FORM 2
The Patents Act 1970
(39 of 1970)
&
The Patent Rules 2003
COMPLETE SPECIFICATION
(See Section 10 and rule 13)
TITLE OF THE INVENTION:
A SENSING AND ACTUATING DEVICE WITH BUILT-IN POWER
GENERATION
APPLICANT:
LARSEN & TOUBRO LIMITED
L&T House, Ballard Estate, P.O. Box No. 278,
Mumbai, 400 001, Maharashtra,
INDIA.
PREAMBLE OF THE DESCRIPTION:
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED

A) TECHNICAL FIELD
[0001] The present invention generally relates to a switch gear applications and particularly to sensing and actuating devices. The invention more particularly relates to thermoelectric devices with built-in power generation system
B) BACKGROUND OF THE INVENTION
[0002] Generally various types of sensors are used to sense a current for measuring the magnitude of the current for protection purposes. These sensors include current transformers, open loop sensors without any secondary winding and closed loop sensors with secondary winding. Both the open and closed loop sensors develop an output voltage using the hall sensors located in the magnetic region. There are other types of current sensors, which use a magneto resistive material to sense the current. The magneto resistive material changes its resistance under the influence of an external magnetic field produced by the current carrying conductor. Similarly an optical sensor uses fiber optic material and coherent light sources to detect the magnetic field created by the current carrying conductor. In all these type of current sensors, the field is sensed through a special core material such as a ferromagnetic material with medium to low permeability especially used for current transformer and open, closed loop Hall Effect sensors. Similarly in other type of current sensors some form of detecting materials such as magnetoresistive and fiber optical materials are used, which surrounds the current carrying conductor.
[0003] The output of the Hall Effect sensors is normally fed to a tripping or actuating device which is separately located from the sensing device. In some current sensors such as current transformer, the heat generated due to copper and iron losses

leads to high temperature rise, which requires for extra class of insulation coordination. Also the heat energy generated goes waste without any utilization.
[0004] Hence there is a need to avoid the magnetic core material surrounding the current carrying part and suitably utilize the extra heat energy developed to convert the heat energy into electric power. Further, there is a need to utilize the extra heat energy to drive the electronic and micro-controller units used in control and protective device. Moreover, there is a need to provide a device which causes actuation of a tripping mechanism at an intended current without the usage of an external protection unit.
[0005] The above mentioned shortcomings, disadvantages and problems are addressed herein and which will be understood by reading and studying the following specification.
C) OBJECTS OF THE INVENTION
[0006] The primary object of the present invention is to provide a current sensing and actuating device with built-in power generation system.
[0007] Another object of the present invention is to provide a current sensing and actuating device to transform the extra heat energy developed during operation to electric power.
[0008] Yet another object of the present invention is to provide a current sensing and actuating device to sense the current flowing through the conductor and the joule heat loss without using any magnetic core surrounding the current carrying path.

[0009] Yet another object of the present invention is to provide a current sensing and an actuating device for protection purpose in the event of a sustained overload or fault condition.
[0010] Yet another object of the present invention is to provide a current sensing and an actuating device to reduce the temperature rise by cooling the heat source during conversion of heat energy into electrical power.
[0011] Yet another object of the present invention is to provide a current sensing and actuating device that causes actuation of a tripping mechanism at an intended current without using an external protection unit.
[0012] These and other objects and advantages of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.
D) SUMMARY OF THE INVENTION
[0013] The above mentioned shortcomings, disadvantages and problems are
addressed herein and which will be understood by reading and studying the following specification.
[0014] The various embodiments of the present invention provide a current sensing and actuating device with built-in power generation system. The sensing and actuating device comprises a thermoelectric generator (TEG) with a series connected N and P thermocouple, an insulator, a terminal corrected to a thermocouple element of the TEG, a conductor bonded with the TEG through the thermal conductive

insulator, a composite actuator and, a compression spring. The device senses the current by thermal means and causes the actuation of the protection unit due to magnetostriction effect of the individual layer of the composite actuator.
[0015] The thermoelectric generator (TEG) is modeled with the current carrying conductor tightly. The conductor is adhered to TEG by means of a highly thermal conductive insulator. The insulator isolates the TEG element from high voltage primary conductor. The actuator is an integral part of the device. The actuator is held by the compression spring, whose one end is connected to the composite strip and other end to the insulator. The actuator senses the magnetic field created by the current carrying parts, which further causes the actuator lever to develop sufficient stroke and force to operate the tripping mechanism.
[0016] According to one embodiment of the present invention, the thermoelectric generator includes a series connected N and P junction thermocouple, connected in an array to create a power generator with adequate wattage. The N and P junction thermocouple elements are connected with respect to each other by means of high electrical conductivity material such as copper, aluminum etc. Each of the N and P junctions is further connected to other junction elements in array using a high electrical conductivity material. This improves the overall output voltage of the thermoelectric generator.
[0017] According to one embodiment, a terminal is connected to the start and end thermocouple element of the thermoelectric generator. The terminal comprises of a silver plated copper conductor. In another embodiment, the insulator is tightly • adhered with the current carrying conductor and the thermoelectric generator. Since the thermoelectric generator is made of a very high thermal conductive material, it

aids in transferring the heat generated at the hot junction of the thermoelectric generator insulator. Under this condition, the lower junction is the cold junction.
[0018] According to one embodiment, the actuator is provided to actuate the tripping mechanism under the influence of magnetic field generated due to current flowing through the conductor. During short circuit condition, the actuator actuates the tripping mechanism associated with a protective device. The actuator consists of three layers each with different magnetostriction coefficient to form a composite strip. The functioning of the actuator is based on the principle of magnetostriction effect in the composite material. The actuator is held by the compression spring, whose one end is connected to the composite strip and other end, to the insulator. Under normal condition, when the current is below 10KA, the spring holds the actuator with a force sufficient to overcome three times of its weight. In the event of a fault, the magnetic field developed is sufficient to cause a positive deflection in the actuator, which overcomes the spring force and actuates the tripping mechanism of a protection unit.
[0019] The actuator senses the magnetic field created by the current carrying part, which further causes the actuator lever to develop sufficient stroke and force to operate the tripping mechanism. The actuator lever consists of a composite material including a ferromagnetic material and an alloy material which are suitably bonded with respect to each other. The magnetic field generated by the current carrying part, develops a differential strain in the alloy as compared to that of the ferromagnetic material. Due to the mutual effect of tension produced in the individual material, the lever of the actuator lifts thus providing the desired stroke to the tripping mechanism.
[0020] According to one embodiment, the device senses the current flowing through the conductor and the joule heat losses without using a magnetic core. The

joule heat loss is sensed by using the thermoelectric generator. The thermoelectric generator converts the sensed extra heat developed in the current carrying parts into electric power, which is then used to drive an electronic or microcontroller units and further to control the protective device. This ensures the maximum utilization of the heat energy developed in the current carrying parts and thus avoids the heat energy from getting wasted. The thermoelectric generator is electrically isolated from the current carrying parts by means of a highly thermal conductive insulated material. The insulating material has thermal properties compatible to the mild steel.
[0021] The response time of the current sensing and actuating device generally varies from a few milliseconds to seconds. The response time of the current sense varies depending on the thermal stabilization of the conducting path. Hence the device is used for protection purpose in the event of sustained overload or fault condition. In some situation, if a delayed thermal overload protection is required, the nonlinear output power of the device is fed to a solenoid followed by a tripping mechanism to provide overload protection with intended time delay.
[0022] According to one embodiment of the present invention, the current sensing and actuation device utilizes the extra heat energy developed in the device by means of transforming the heat energy into electric power. The electric power is further utilized to drive the electronic and micro-controller units used in control and protective device. The conversion of heat energy into electrical power serves the purpose of cooling the heat source thereby reducing the temperature rise. The device actuates the tripping mechanism at an intended current without the usage of a protection unit.

E) BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The other objects, features and advantages will occur to those skilled
in the art from the following description of the preferred embodiment and the accompanying drawings in which:
[0024] FIG. 1 shows a sectional view of a current sensing and an actuating device, according to one embodiment of the present invention.
[0025] FIG. 2 shows a thermoelectric generator of FIG1, according to one embodiment of the present invention.
[0026] FIG. 3 shows an insulator of FIG.1 according to one embodiment of the present invention.
[0027] FIG. 4 shows an actuator of FIG. 1 according to one embodiment of the present invention.
[0028] FIG. 5 shows an electron and hole flow in the N and P type thermocouple element, according to one embodiment of the present invention.
[0029] FIG. 6 shows a transient thermoelectric analysis demonstrating the current distribution in the current carrying conductor due to thermoelectric effect, according to one embodiment of the present invention.
[0030] FIG. 7 shows a transient thermoelectric analysis to illustrate a steady state temperature rise due to joule heat loss corresponding to the fault current according to one embodiment of the present invention.

[0031] FIG. 8 is a graph indicating an output voltage of the thermoelectric generator according to an embodiment of the present invention.
[0032] FIG. 9 shows a transient thermoelectric analysis to illustrate the current distribution in the thermoelectric generator according to one embodiment of the present invention.
[0033] FIG. lOshows a transient thermoelectric analysis to illustrate the temperature due to joule heat loss in the thermoelectric generator according to one embodiment of the present invention.
[0034] FIG. 11 shows a transient thermoelectric analysis to illustrate the voltage output of the thermoelectric generator according to one embodiment of the present invention.
[0035] FIG. 12 shows a transient thermoelectric analysis to illustrate the voltage drop across the terminal according to one embodiment of the present invention.
[0036] FIG. 13 shows a transient thermoelectric analysis to illustrate the thermocouple differential temperature according to one embodiment of the present invention.
[0037] FIG. 14 shows a current distribution across the sensor terminal according to one embodiment of the present invention.
[0038] FIG. 15 shows the temperature due to joule heat loss across the sensor terminal according to one embodiment of the present invention.

[0039] FIG. 16 shows the potential voltage drop across the sensor terminal according to one embodiment of the present invention.
[0040] FIG. 17 is a graph illustrating a variation of the temperature of the conductor with respect to the primary current loaded to the sensor according to one embodiment of the present invention.
[0041] FIG. 18 is a graph illustrating the variation of the secondary current with respect to the primary current loaded to the sensor according to one embodiment of the present invention.
[0042] FIG. 19 is a graph illustrating the variation of the primary current with respect to the secondary voltage in the sensor according to one embodiment of the present invention.
[0043] FIG. 20 is a graph illustrating the secondary burden of the sensor with respect to that of the primary current loaded according to one embodiment of the present invention.
[0044] FIG. 21 shows a current density distribution of the sensor with a thermoelectric P and N type thermocouple element according to one embodiment of the present invention.
[0045] FIG. 22 and 23 shows temperature of the conductor and joule heat loss with PbTe as a thermocouple element according to one embodiment of the present invention.

[0046] FIG. 24, 25, 26 and 27 shows the temperature, secondary voltage, current and VA of the sensor with PbTe as a thermocouple element according to one embodiment of the present invention.
[0047] FIG. 28 shows a current distribution of the sensor using SiGe as the P and N type thermocouple element according to one embodiment of the present invention.
[0048] FIG. 29 shows temperature distribution in the sensor due to joule heat loss using SiGe as thermocouple element according to one embodiment of the present invention.
[0049] FIG. 30, 31, 32 and 33 shows the temperature, output voltage, current and VA of the sensor with SiGe as a thermocouple element according to one embodiment of the present invention.
[0050] FIG. 34 shows a lower differential temperature with SiGe as a thermocouple element according to one embodiment of the present invention.
[0051] FIG. 35 shows an internal force developed in the negative magnetostriction metal according to one embodiment of the present invention.
[0052] FIG. 36 shows the magnetic field distribution on the actuator due to current flowing through the conductor according to one embodiment of the present invention.
[0053] FIG. 37 shows an illustration of the interna! forces and the bending moments in the trimetal when subjected to a magnetic field according to one embodiment of the present invention.

[0054] FIG. 38 and 39 shows the maximum force and stroke developed by the actuator due to material combination according to one embodiment of the present invention.
[0055] FIG. 40 and 41 shows an exemplary illustration of the internal strain and stress developed in the material due to magnetic field generated by the current carrying conductor according to one embodiment of the present invention.
[0056] Although specific features of the present invention are shown in some
drawings and not in others. This is done for convenience only as each feature may be combined with any or all of the other features in accordance with the present invention.
F) DETAILED DESCRIPTION OF THE INVENTION
[0057] In the following detailed description, reference is made to the
accompanying drawings that form a part thereof, and in which the specific embodiments that may be practiced is shown by way of illustration. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments and it is to be understood that the logical, mechanical and other changes may be made without departing from the scope of the embodiments. The following detailed description is therefore not to be taken in a limiting sense.
[0058] The various embodiments of the present invention provide a sensing and actuating device with built-in power generation system. The sensing and actuating device comprises a thermoelectric generator (TEG) with a series connected N and P thermocouple, an insulator, a terminal connected to a thermocouple element of the

TEG, a conductor bonded with the TEG through the thermal conductive insulator, an composite actuator and, a compression spring. The device senses the current by thermal means and causes the actuation of the protection unit due to magnetostriction effect of the individual layer of the composite actuator. The thermoelectric generator (TEG) is modeled with the current carrying conductor tightly adhered to it. The conductor is adhered to TEG by means of a highly thermal conductive insulator. The insulator isolates the TEG element from high voltage primary conductor. The actuator is an integral part of the device. The actuator is held by the compression spring, whose one end is connected to the composite strip and other end, to the insulator. The actuator senses the magnetic field created by the current carrying part, which further causes the actuator lever to develop sufficient stroke and force to operate the tripping mechanism.
[0059] FIG. 1 shows a sectional view of a current sensing and an actuating device 100, according to one embodiment of the present invention. The device 100 senses the current by thermal means and causes an actuation due to magnetostriction effect of the individual layer of the composite actuator. The device 100 comprises of a thermoelectric generator 101, an insulator 103, a terminal 102, a conductor 104, a spring 105 and an actuator 106.
[0060] FIG. 2 shows a thermoelectric generator 101 of FIG. 1 according to one embodiment of the present invention. The thermoelectric generator 101 consists of series connected N and P junction thermocouple, connected in array form so as to create power generator 101 with adequate wattage. The N and P junction 201, 202, thermocouple elements are connected with respect to each other by means of high electrical conductivity material such as copper, aluminum etc.

[0061] Each of the N and P junctions 201, 202 is further connected to other junction elements in array form using any high electrical conductivity material. This improves the overall output voltage of the thermoelectric generator 101. The N and P type thermocouple are made out of special alloy composition such as BiTe, PbTe and SiGe material. Depending upon the temperature range, suitable material can be used as P and N type element. For an instance, BiTe can be used up to a differential temperature of less than 423K. Similarly PbTe and SiGe can be used up to a differential temperature of less than 923K and 1273K. Beyond the intended range of temperature, the basic characteristics and properties of the alloy gets distorted. Both the P and N type elements are derived from these alloys by means of suitable doping.
[0062] According to one embodiment, a terminal 102 is connected to the start and end thermocouple element of the thermoelectric generator 101. The terminal 102 comprises of a silver plated copper conductor.
[0063] FIG. 3 shows an insulator 103 of FIG.l. The insulator 103 is tightly adhered with the current carrying conductor 104 and the thermoelectric generator 101 according to one embodiment of the present invention. The thermoelectric generator 101 is made of very high thermal conductive material, it aids in transferring the heat generated at the hot junction of the thermoelectric generator 101 to the insulator 103. Under this condition, the lower junction is the cold junction, which initially is at ambient temperature of 300K. The insulator 103 electrically isolates the high voltage current carrying conductor 104 from the thermoelectric generator 101. There are various types of material available, which can be used as insulator 103 but the best material as commercially accepted is the aluminum nitride ceramics, which has very high thermal conductivity in the range of 140- 180 w/m/k,

[0064] FIG. 4 shows an actuator 106 of FIG. 1. The actuator 106 is provided to actuate the tripping mechanism under the influence of magnetic field generated due to current flowing through the conductor according to one embodiment of the present invention. During short circuit condition, the actuator 106 actuates the tripping mechanism associated with a protective device 100. The actuator 106 consists of three layers each with different magnetostriction coefficient to form a composite strip. The actuator 106 is held by the compression spring 105, whose one end is connected to the composite strip and other end, to the insulator 103. Under normal condition, when the current is below 10KA, the spring 105 holds the actuator 106with a force sufficient to overcome 2 to 3 times of its weight. In the event of a fault, the magnetic field developed is sufficient to cause a positive deflection in the actuator, which overcomes the spring 105 force and actuates the tripping mechanism of a protection unit.
[0065] The actuator 106 is an integral part of the device 100. The actuator 106 senses the magnetic field created by the current carrying part, which further causes the actuator 106 lever to develop sufficient stroke and force to operate the tripping mechanism. The actuator 106 lever consists of composite material consisting of a ferromagnetic material and special alloy which are suitably bonded with respect to each other. The magnetic field generated by the current carrying part, develops 10 to 20% differential strain in the alloy as compared to that of the ferromagnetic material. Due to the mutual effect of tension produced in the individual material, the lever of the actuator 106 is lifted thus providing the desired stroke to the tripping mechanism. Several combinations of metal and alloy are tried for development of the actuator 106 lever, which shows variation in the force developed due to magnetostriction effect.

[0066] FIG. 5 shows the electron and hole flow in the N and P type thermocouple element, according to one embodiment of the present invention. When the current flows through a conductor, the joule heat loss is sensed by the device 100. The high thermal conductive material such as Aluminum nitride ceramics or by other means adhered to the conductor 104and thermoelectric generator 101 transfers the heat loss to the hot junction of the thermoelectric generator 101 (TEG). The lower end of the TEG initially remains at ambient temperature, thereby creating a differential temperature between the hot and cold junction. The differential temperature excites the electrons to flow from the P type to N type element and thereby absorb the heat produced at the hot junction and expel it at cold junction.
[0067] The mobility of electrons between the elements causes a flow of current from N type element to P type element. Due to this thermoelectric effect, depending upon the seebeck coefficient of the individual P and N type element, each of the thermocouple develops output voltage in mV rang.. Several such thermocouples are connected in series in rectangular array form to increase the output of the TEG up to few volts. At rated thermal current the output volta,ge is in few mV as the conductor 104 temperature is of the order of 338K (assuming a 40° C temperature rise) whereas at overload & abnormal condition, at 1KA, the steady state temperature of the conductor 104 reaches to 1050K.The output voltage depending upon the material of the thermocouple element, is in the order of few volts. Unlike to conventional measuring current transformer, the response time of the sensor depends upon the thermal stabilization of the current carrying conductor. At low current, the response time of the sensor could be of the order of few seconds and at high current it is in the order of few milliseconds. Hence application of the current sensor is for indication and protection circuit rather than for measuring purpose. The ratio of primary to secondary current will depend upon the burden attached to the output of sensor. Also as the ambient temperature varies, the sensitivity of the device 100 also varies.

[0068] At rated and overload condition, the flux density is in the order of few mT. The longitudinal strain developed in the individual layer of the composite material is 1% of the total length of the actuator. The deflection and the force due to 1% strain is in few μm and gm. However, under abnormal condition at 15KA and above, the flux density in the actuator 106 is of the order 0.33T to 0.7T. The longitudinal strain developed due to magnetostriction is up to a maximum of 10% depending upon the material selected. The deflection and force that can be obtained by the actuator 106is 0.75mm to 12.1mm & 0.5 to 7.6Kg respectively. Several combination of material is tried for development of composite strip, which is used for actuator 106 of the device 100. The actuator 106 with composite strip formed out of Mild steel-MSMA and CRNGO — Mild steel, provides the maximum stroke and actuation force,
[0069] According to the present invention, the sensing and actuation device 100 is obtained by means of a suitable improvement to an existing composition of matter. To realize the functioning of the device 100 as a sensor, the thermoelectric generator 101 is modeled with a current carrying conductor 104 tightly adhered to it by means of a highly thermal conductive insulator 103. The insulator 103 isolates the TEG element from high voltage primary conductor. Three different N and P type thermocouple element such as Bismuth telluride, lead Telluride and silicon germanium is used for the purpose. The functionality of the sensor is initially validated through electro-thermal static and transient analysis using ANSYS versionl 2. The results of ANSYS analysis are plotted and shown in FIG. 6 to FIG. 33.
[0070] A similar analysis is done to understand the functioning of the device 100 as an actuator 106 based on the principle of magnetostriction effect in the composite material. Functioning of the device 100 as an actuator 106 is validated through

electromagnetic analysis, which provides the parameters such as magnetic field distribution in the composite material due to current flowing in the conductor. Corresponding to the B and H obtained from the above analysis, λ of each material is selected from the magnetostriction characteristics curve suitable for various materials. The internal force developed in each layer of the actuator 106 due to stress in the material is then calculated. A detailed structural analysis is performed with the internal force acting upon the actuator 106 to find out the resultant force and stroke for various combination of material. The results of the analysis are shown in FIG. 36 to FIG. 41 to support the development.
[0071 ] FIG. 6 shows a transient thermoelectric analysis to demonstrate the current distribution in the current carrying conductor 104due to thermoelectric effect, according to one embodiment of the present invention. In order to understand the current sensing phenomenon, a sensing unit is rnodeled without inclusion of the actuator 106 and spring 105 as shown in FIG. 6, The model is then analyzed for thermoelectric analysis (static type) in ANSYS version 12. The thermoelectric static analysis is performed for 1KA current loaded to the current carrying conductor, to which the generator 101 is tightly adhered. The material for P and N type element of the thermocouple is chosen as BiTe for the above analysis. FIG. 6 shows the current distribution in the current carrying conductor.
[0072] FIG. 7 shows a transient thermoelectric analysis to illustrate a steady state temperature rise due to joule heat loss corresponding to the fault current according to one embodiment of the present invention. FIG. 8 shows an output voltage of the thermoelectric generator 101 according to one embodiment of the present invention. The maximum output voltage of 1.12 volt is obtained. On the same model, a transient thermoelectric analysis is done by means of loading the conductor 104 with 0.474KA for duration of 335 ms in order to restrict the temperature below the

intended range of BiTe thermocouple element, which is < 450K. The detail results are shown in the subsequent figures.
[0073] FIG. 9. 10 and 11 shows a transient thermoelectric analysis to illustrate the current distribution, temperature due to joule heat loss and voltage output of the thermoelectric generator 101, which senses the current flowing through the conductor according to one embodiment of the present invention. As shown in FIG. 10, the temperature of the conductor 104 and insulator 103 surrounding to it is reduced to temperature (325.6K) very near to the ambient temperature, for instance 300K. This reduction in temperature is because of heat transfer by the insulator 103 and absorption of heat by the thermocouple element to the hot junction of the thermoelectric generator 101. The surface of the insulator 103 holding the thermocouple is increased to 377.3K.
[0074] FIG. 12 shows a transient thermoelectric analysis to illustrate the voltage drop across the terminal 102 according to one embodiment of the present invention.
[0075] FIG. 13 shows a transient thermoelectric analysis to illustrate the thermocouple differential temperature according to one embodiment of the present invention. The thermocouple of the differential temperature is 183 K, which develops an output voltage of 4V. In actual case the output voltage varies with the variation in the seebeck coefficient, thermal conductivity and electrical conductivity of the P and N type element, which normally varies with temperature. The study was further extended to understand the effect of resistive burden of lohm upon the performance of sensor VA. Transient analysis was done for a current of 0.474K for 0.39 s with 1 ohm resistor connected to the output of the sensor.

[0076] FIG, 14, 15 and 16 shows a current distribution, temperature, joule heat loss and potential drop across sensor terminal 102.
[0077] FIG. 17, 18, 19 and 20 shows a variation of temperature of the conductor, secondary current, output voltage and secondary burden of the sensor with respect to that of the primary current loaded according to one embodiment of the present invention. The temperature of the conductor 104 steadily increases from ambient temperature to 150°C. During the rise in temperature, the basic property of the material such as the seebeck coefficient, the electrical conductivity and the thermal conductivity, varies with the temperature. Hence instead of steady rise in voltage with respect to primary current, the voltage and the VA obtained is nonlinear in nature. The effect of material property variation can also be prominently seen in the secondary current curve, which is not linear with a fixed slope. The ratio of primary to secondary remains constant after the rated current of the sensor. FIG. 17, which shows that the operating temperature range of sensor with BiTe is up to 150°C. The maximum output voltage and current that can be derived from this sensor is 0.2A at 0.5 Volt. The VA rating is less than 0.14.
[0078] FIG. 21 shows a current density distribution of the sensor with PbTe as the thermoelectric P and N type thermocouple elements according to one embodiment of the present invention. The current loaded into the conductor 104 is 1K.A for 710ms. An electro-thermal analysis is done for P and N type PbTe material. As compared to BiTe material, it is used for higher range of temperature from 300K to 923K. At room temperature, the resistivity is 40% that of P type BiTe (0.68e-5 ohm-m as against 1.72e-5 ohm-m). The seebeck coefficient of P type PbTe is 285.5μ.V/K as compared to P type BiTe, which is of 220μ A7K. Above room temperature, the seebeck coefficient of N type BiTe material reduces with temperature until it gets saturated to a value of 85μ,V/K as against N type PbTe material whose seebeck

coefficient remains constant in the range 200 to 249ΜV/K irrespective with change in temperature. From the analysis performed, it can be confirmed that the PbTe material not only increases the range of operating temperature of the thermoelectric generator 101 but also improves the output voltage and power of the sensor. This is because the output voltage of the thermoelectric generator 101 depends upon the seebeck coefficient, which is higher in case of PbTe as compared to BiTe.
[0079] FIG. 22 and 23 shows a temperature of the conductor 104due to joule heat loss with PbTe as a thermocouple element according to one embodiment of the present invention. After thermal stabilization of the sensor, the steady state temperature of the conductor 104 and surrounding insulator 103 is 406K. The heat generated is transferred through the insulator 103 and is expelled at the hot junction of the thermoelectric generator 101. At the hot junction of TEG, the temperature observed to be 609 K and across the P and N type element, temperature observed to be 914K. The differential temperature of the sensor observed to be 508K, which is much below the operating range of PbTe materia].
[0080] FIG. 24, 25, 26 and 27 shows the temperature, secondary voltage, current and VA of the sensor with PbTe as a thermocouple element according to one embodiment of the present invention. The operating temperature range of PbTe is up to 650°C. The maximum secondary voltage and current observed to be 1.4V and 1.9A. The VA rating of the sensor with this material is 2.8 as against 0.14. This shows the superiority of PbTe TEG element over the BiTe material. Thus the output power of sensor with PbTe material is approximately 20 times higher to that with BiTe material.
[0081] Further an analysis is performed using a sensor with SiGe as thermoelectric material. The operating temperature band of SiGe is even higher than

that of the PbTe TEG element. The sensor made out of SiGe rises up to a maximum operating temperature of 1273K.
[0082] The resistivity of SiGe is 20 to 25% to that of BiTe and 15% to that of PbTe. Hence SiGe is a high electrical conductive material as compared to BiTe and PbTe. For the same voltage drop across the PN junction thermocouple, the current drawn by these elements will be higher. The thermal conductivity of SiGe material is 3.5 times higher than that of BiTe and PbTe. This leads to increase in the temperature gradient of the TEG. Hence for the same seebeck coefficient, the output voltage will be higher to that of other material. Also the power output of the sensor is expected to be higher with SiGe TEG element. The seebeck coefficient of N type SiGe at room temperature is similar to that of the PbTe and is lower to that of the BiTe. As the temperature increases, the seebeck coefficient of BiTe reduces drastically before it gets saturated. On contrast to this, the seebeck coefficient of PbTe and that of SiGe increases with temperature until it gets saturated at a higher value of 240 - 300μV/k. This shows the superiority of PbTe and SiGe as far as the seebeck coefficient is concerned.
[0083] FIG. 28 shows current distribution of the sensor using SiGe as the P and N type thermocouple element according to one embodiment of the present invention. The current corresponding to the density as shown in the figure is 1KA for 710ms. FIG. 29 shows the temperature distribution in the sensor due to joule heat loss using SiGe as thermocouple element. The temperature across the conductor 104and that of the insulator 103 observed to be 383.5K whereas the thermocouple element temperature observed to be 863K. Differential temperature between the hot and cold junction of the thermocouple element, is observed to be 480K. Corresponding to the differential temperature, the output voltage of the sensor with SiGe is compatible as

that of the PbTe. However due to higher electrical conductivity, the current drawn by the thermocouple elements would be higher.
[0084] FIG. 30, 31, 32 and 33 shows the temperature, output voltage, current and VA of the sensor with SiGe as a thermocouple element according to one embodiment of the present invention. The operating range of temperature for sensor with SiGe as the thermocouple material is up to 1273K. Owing to this, the current rating of the sensor is 381A as compared to BiTe and PbTe, whose rating is limited to 150A and 320A respectively. Due to higher current rating, the output parameters are expected to be high. At a primary current rating of 279A, the secondary current, voltage and VA of the sensor observed to be 3A, 1 V and 3.1 VA respectively. With the same output voltage as that of PbTe, the output current is higher because of lower resistivity of the P and N type SiGe thermocouple element. The nonlinearity observed in the output voltage is due to variation in the properties (with respect to operating temperature) of the P and N type SiGe material used in the sensor.
[0085] The present invention restrict its scope within these three material selected for the sensor thermocouple element. Further, improvement in performance can be achieved by using special material with higher seebeck coefficient, operating temperature range and material with least effect with respect to temperature variation. Also the rating of the sensor as mentioned above is for continuous inspection of the circuit. In case of intermittent duty and short circuit condition, the rating of the sensor is in the order of KA for few ms provided the power input of the sensor is maintained within its specified range, which for BiTe, PbTe and SiGe are 5.7,61 and 115.6 watt respectively.
[0086] The test sample consists of thermoelectric generator 101 with size 40 x 40 x 4 and total area of 1600 mm2. Total number of thermocouple element connected in

series is 127 with a current density of 0.079A/mm2. The differential temperature between the hot & cold junction of the thermoelectric generator 101 was maintained at 45°C. With this differential temperature, the output voltage observed to be 1.17 V. FIG. 34 shows the measured output voltage of the TEG device with respect to differentia! temperature.
[0087] The present invention is towards development of an actuator, which is based upon the principle laid down as per magnetostriction effect. The magnetostriction effect provides very high force even at very low stroke. It provides the intended longitudinal strain in a strip due to alignment of the dipoles within a single domain, along the direction of the magnetic field applied. The magnetostriction coefficient of the single domain, is given by:
λ = 3/2*).s ({cos2Ø}av - 1/3) - 3/2* λs ({cos2Ø}o - 1/3) Where 0 is the angle between the direction of magnetization and the direction in which the change in length is measured. {cos20}av represents the distribution of the domain at any time and {cos20}o represents the initial distribution of the domain. It is assumed that magnetostriction is independent of the crystallographic direction of magnetization and that the change in volume is zero. The zero point of λ,l is equal to the longitudinal change in length λs when 0 = 0, when the material gets saturated.
[0088] Since the actuator 106 comprises of tri-metal with different magnetostriction coefficient, in the event of magnetic field applied along its length, it causes change in the length of the individual material, which are ferromagnetic in nature. The magnetostriction coefficient of these materials can be positive and negative depending upon their characteristics and behavior. Due to difference in strain developed in individual material and tension between the layers, causes an upward deflection of the actuator 106 normal to the direction of the magnetic field applied. The magnetic field is developed due to the current flowing through the

current carrying conductor, as shown in FIG. 1. Several ferromagnetic materials are tried to find out the optimal combination of trimetal, which provides the highest force and stroke. Typical material that were selected for the tri-metal actuator, is mild steel, CRNGO electrical steel, magnetically shape memory alloy, Tromadur 526 and Terfenol - T (TbO.3DyO.7FeO.9). Eight possible combinations of tri - metal were developed from the material as mentioned.
[0089] Mild steel is a low permeability (or = 2000) material with high coercivity and poor Br and finds application in current transformers and low grade transformers. Mild steel has a Negative magnetostriction coefficient in the order of 5 to 8 μ.m/m and high young's modulus of elasticity of 210 GPa. Under the influence of magnetic field applied along its longitudinal direction, as the field intensity and hence the magnetic flux density increases, the negative magnetostriction coefficient increases in a nonlinear way, which saturates to -l2.5μm/m at a flux density of IT. Due to its negative value the stress developed in the material causes a tension, which increases and hence leads to increase in length of the metal.
[0090] FIG. 35 shows the internal force developed in the negative magnetostriction metal according to one embodiment of the present invention. The CRNGO electrical steel (with 3% silicon content) is a medium permeability (μ.r = 5000 to 7000) material with coercivity in the range of few hundred A/m and moderate Br. Mostly it is used in electromagnets, actuators etc. Unlike to mild steel, it has a positive magnetostriction coefficient in the order of 10u.m/m and lower young's modulus of elasticity of 124-150 GPa. As the magnetic field intensity is increased, the magnetostriction coefficient of the material increases steadily in a nonlinear way until it saturates at lOKA/m. Depending upon the oxidation and element content, the magnetostriction coefficient (λ) of the material vary from 5 to

20μm/m. Due to the positive λ value, stress developed in the material causes a tension, which reduces with increase in magnetic field intensity.
[0091] Probably the highest positive λ (100μ.m/mm) material, which is available is the magnetically shape memory atloy, which is an alloy comprising of Ni, Mn and Ga material. It has a very low permeability of the order 1.5 - 40, which is several times lower than that of the other magnetic materials. The coercivity of this material is in the range of 400 KA/m and has low young's modulus of elasticity of 7.7GPa. This makes the material highly suitable for actuator, which can produce force in several KN for a lower stroke in few mm. The magnetic field is applied either in the longitudinal or lateral direction depending upon the requirement. With flux density, the λ value increases in a nonlinear way until it saturates to 0.1 m/m at IT. Due to the positive λ value it produces a tension, which reduces with increase in flux density.
[0092] Yet there is another material such as plastic bonded magnetic material commercially known Tromadur 526, which is made of ferrite along with polyamide and PPS through injection molded process. Tromadur 526 material has very low young's modulus of elasticity in the range of 2-6 GPa as compared to mild steel. Being an extruded composition of ferrite and plastic material, its magnetic behavior is similar to that of magnetic insulator 103. Hence the relative permeability of the material is 1.01 with lower Br (0.165T) and higher coercivity (130KA/m). Similar to that of mild steel, Tromadur 526 exhibits negative λ value of - 200 to -252μ.m/m, which is 20 to 25 times higher and also increases the tension in the material as the magnetic field increases.
[0093] Terfenol - T exhibits higher positive λ value (1000-2000μm/m) as compared to all the material except MSMA and has moderate young's modulus of elasticity of 25 - 35 GPa. Similar to that of the Tromadur 526, Terfenol - T material

has lower relative permeability of the order 3-10. The Coercivity of Terfenol - T is in the range of few (50-200) KA/m. Owing to positive λ, the tension produced in the material decreases with magnetic field.
[0094] The various combination of the actuator 106 with different magnetic material is given in table-1 below, which provides information about the individual layer of actuator 106with length L = 40mm and width W = 1.8mm.

Combination Material Thickness(mm)
First Second Third First Second Third
Layer layer layer Layer layer layer
Mild Mild
1 steel MSMA steel 1.2 1.8 1.2
Mild
2 MSMA steel MSMA 1.2 i.8 1.2
3 MSMA CRNGO MSMA 1.2 1.8 1.2
4 MSMA CRNGO MSMA 1.2 0.6 1.2
Tromadur
5 MSMA 526 MSMA 1.2 0.6 1.2
Tromadur
6 Terfenol 526 Terfenol 1.2 0.6 1.2
Tromadur Mild Tormadur
7 526 steel 526 1.2 0.6 1.2
Mild
8 CRNGO steel CRNGO 1.2 0.6 1.2

[0095] A static electromagnetic analysis is done on the various combinations (1-8) of actuator 106 so as to understand the static magnetic field distribution in the individual layer of the actuator. The analysis is done at a current of 1 OKA and 50KA.
[0096] Table-2 shows the flux density and magnetic field intensity of various combination of material at fault level of 15KA. Figure - 35 shows the magnetic fiefd distribution on the actuator 106 due to current flowing through the conductor.

Magnetic parameter at 15KA due to various combination of material
Combination number Material combination H(KA/m) B(T)
1 MILD STEEL(1.2)+MSM(0.6)+MILD STEEL(1.2) 271.11 0.42
2 MSM(1.2)+Mildsteel(0.6)+MSM(1.2) 271.19 0.70
3 MSM(1.2)+CRNGO(1.8)+MSM(1.2) 271.22 0.34
4 MSM(1.2)+CRNGO(0.6)+MSM(1.2) 57.07 0.46
5 MSM(1.2)+TROMADUR(0.6)+MSM(1.2) 264.49 0.33
6 TERFNOL(1.2)+TROMADUR(0.6)+TERFNOL(1.2) 54.96 0.27
7 TROMADUR(1.2)+Mild stcel(0.6)+TROMADUR(1.2) 264.77 0.59
8 CRNGO(1.2)+Mild steel(0.6)+CRNGO(l .2) 56.24 0.30
Table - 2
[0097] As mentioned above, the magnetostriction coefficient of various materials depend upon its magnetic field intensity and hence upon the flux density, which varies in a nonlinear manner. Corresponding to the above values of B& H as shown

in table - 2, X of different material was selected from X Vs H curve. This is because X of a magnetostrictive metal is a complicated three-dimensional function of the magnetic field intensity H and the stress tensor in the metala, i.e. λ. = λ(H, a). Composite strips employing metals having magnetostriction which depends on normal stresses are not likely to give linear response to an applied magnetic field. This is so because the non-uniformity of normal stresses during bending of the strip due to a magnetic field. This is more so in the case of temperature-compensated strip where different initial temperature changes result in different initial thermal stresses. Dependence of λ also on a makes it impossible to accurately determine the radius of curvature of the bent composite strip when the magnetic field is applied. Subsequently, only two cases are taken into consideration
[0098]
λ is proportional to the magnetic field, i.e.λ= λ 'H
Where
λ = dA/dH = constant.
(11) λ is a function of H only, i.e. λ=λ (H)
The first case is applied at lower magnetic field intensities before a saturation
condition is approached. In first case, a composite strip having a linear response to a
magnetic field is used. In second case, the linear response is not achieved due to the
nonlinear behavior of X with respect to the H. In both cases it is possible to
determine the radius of curvature and bending stresses of the trimetal as function of
the magnetic fields.
[0099] FIG. 37 shows an internal forces and bending moments in the trimetal, when subjected to a magnetic field H according to one embodiment of the present invention. In case λ 1>λ 2 for a given magnetic field intensity, the trimetallic strip becomes convex in an upward direction and vice versa. According to the principle of

superposition of linear elasticity, the stress and strains which develop due to the application of the magnetic field are algebraically additional to those which rise because of temperature changes. Neglecting the thermal effect, the stresses and strains upon the material is created due to the magnetic field only. The internal forces in the bent metallic strip can be reduced to the force Fi and the couple Mi.
[00100] Since every cross section of the bent trimetallic strip is in equilibrium, the
sum of the forces in the z-direction is given by
Fl - F2 + F3 = 0 1
The sum of the moments due to Fl, F2 and F3, taken for the purpose of convenience with respect to point A, should be equal to the sum of the bending moments:

Simple beam-bending theory gives the relationships:

Where Ii and ri are the moment of inertia and the radius of curvature of the ith metallic strip respectively. Since the radius of curvature of a single strip is much greater than that of the thickness of the composite strip, the sum of moments will be equal to a resultant moment with average radius of curvature of the trimetal. Consequently equation (2) will have the form:

The RHS of equation (3) is sum of the bending moment.
[00101] The equality of the longitudinal strains of two adjoining metallic strips at their interface gives two equations. When the behavior of the magnetostrictive


The equality of the strains at the interface of metals 2 and X gives the equation:

metals is according to case (I), the equality of longitudinal strains at the interface of metals 1 and 2 results in the equation:
[00102] Equations (1), (3), (4) and (5) can be considered as four linear algebraic equations with four unknown: 1/r, Fl, F2 and F3. The equations are valid only when magnetostrictive materials do not experience a noticeable change in Young's modulus while being magnetized.
[00103] Solving the above four equations will result into a state variable equation
AX = B
Where



Solution for the equation is X = A"'B, which calculates the internal force developed in each layer of the actuator. Table - 3 shows the internal force developed in the actuator 106due to magnetostriction effect in the individual layer. Using the calculated internal force, static structural analysis is done on the actuator 106 to find out the resultant force and stroke developed by the actuator. The analysis is done using ANSYS version 12,

8 5.66E-07 -9.00E-06 5.66E-07 'HI 9,fifi '111

combination of material

Combination number D(m/m) first layer □ (m/m)
second
layer D(m/m) third layer Force(N) F, Force(N) F2 Force(N) Fj
1 -9.00E-06 0.00E+00 -9.00E-06 30.46 60.7 30.27
2 0.00E+00 -9.00E-06 0.00E+00 15.43 158.6 174
3 0.00E+00 5.66E-07 O.OOE+00 4.83 9.66 4.83
4 0.00E+00 5.66E-07 0.00E+00 4.19 8.38 4.19
5 0.00E+00 -5.00E-05 0.00E+00 28.2 56.3 28.2
6 0.00E+OO -5.00E-05 0.00E+00 29.4 58.8 29.4
7 -5.00E-05 -9.00E-06 -5.00E-05 37.1 74 36.9

Table - 3 [00104] Table - 4 and 5 shows the force and stroke developed by the actuator 106 due to the internal stress in the material owing to magnetostriction effect. From the data obtained from the structural analysis, the maximum force and stroke is observed in combination 8, which represents actuator 106 with composite material consisting of CRNGO and Mild steel. The individual layer consists of CRNGO (1.2mm thick) + Mild steel (0.6mm thick) + CRNGO (1.2mm thick). The maximum force and stroke observed to be 7.6 Kg and 11.5mm. The combination which represents actuator 106 with composite material consisting of MSM and Mild steel provides maximum force and stroke of 2.43Kg and 12.1mm. The worst combination of material observed in 4 & 3, where the actuator 106 forces are in few gm and stroke less than or equal to 0.1mm. Actuator 106with material combination 1,5,6,7, shows moderate force & stroke, which is less than or equal to 650gm & 0.8mm respectively.

Force obtained at 15KA due to various combination of material
Combination number Material combination Force(kg)
4 MSM( 1.2)+CRNGO(0.6)+MSM( 1.2) 0.0737
3 MSM( 1.2)+CRNGO( 1.8)+MSM( 1.2) 0.0849
5 MSM(1.2)+TROMADUR(0.6)+MSM(l .2) 0.4957
6 TERFNOL( 1,2)+TROMADUR(0.6)+TERFNOL( 1.2) 0.5168
1 MILD STEEL(1.2)+MSM(0.6)+MILD STEEL(!.2) 0.5319
7 TROMADUR(1.2)+Mild steel(0.6)+TROMADUR( 1.2) 0.6494
8 CRNGO(l .2)+Mild steel(0.6)+CRNGO(l .2) 7.6110
2 MSM(1.2)+Mild steel(0.6)+MSM(l .2) 2.4350

Stroke obtained at 15KA due to various combination of material
Combination number Material combination Stroke(mm)
4 MSM( 1.2)+CRNGO(0.6)+MSM(l .2) 0.1110
3 MSM( 1.2)+CRNGO( 1.8)+MSM(l .2) 0.1290

5 MSM(L2)+TROMADUR(0.6)+MSM(1.2) 0.7500
6 TERFNOL(l .2)+TROMADUR(0.6)+TERFNOL(1.2) 0.7830
1 MILD STEEL(1.2)+MSM(0.6)+MILD STEEL(1.2) 0.7920
7 TROMADUR(1.2)+MiId steei(0.6)+TROMADUR(l .2) 0.9720
8 CRNGO(l .2)+Mild steel(0.6)+CRNGO(l .2) 11.5000
2 MSM(1.2)+Mildsteel(0.6)+MSM(1.2) 12.1400

Table - 5 [00] 05J FIG. 38 and 39 shows the maximum force and stroke developed by the actuator 106 due to the material combination according to one embodiment of the present invention. FIG. 40 and 41 shows the internal strain and stress developed in the material due to magnetic field generated by the current carrying conductor 104at 15KA. The internal strain developed by the actuator 106is -3.7%, which is due to the negative magnetostriction coefficient material Mild steel, which has higher tension as compared to positive λ material CRNGO. The middle layer made out of mild steel is under higher tension as compared to the upper layers and lower layer made out of CRNGO. The stress developed in the actuator 106 due to domain orientation is 0.87e8 N/m2.This corresponds to an internal longitudinal force of 0.484KN, which match with the calculated force developed by the individual upper & lower layer.

[00106] The device 100 as disclosed is a current sensor which senses the current thermally through N and P type thermocouple element array attached to a high thermally conductive insulator 103, which is tightly adhered to current carrying parts. The continuous rating of the sensor is from 3 range of 150 to 380A depending upon the material selected for the thermocouple element. Intermittent current and short circuit level of the sensor could be in few KA for ms. The current ratio of the sensor will be a nonlinear characteristics unlike to a current transformer, which has linear characteristics up to a certain range of primary current. The sensor can be used for protection purpose in addition to measuring the current. Maximum continuous secondary current, voltage and VA that can be derived from the sensor is in the range of 0.2A to 3A, 0.5 to 1.4V and 0.14 to 3.1 VA depending upon the material selected for the thermocouple element. In addition to acting as a sensing device, the device 106 can also be used as an actuator with maximum force of 7.6 Kg and stroke of 11.5 mm.
G) ADVANTAGES OF THE INVENTION
[00107] The various embodiments of the present invention provide a sensing and actuating device with built-in power generation system. Accordingly the device utilize the extra heat energy developed in the current carrying parts to transform it into electric power to drive an electronic and micro-controller unit for control and protective device. The device senses the current flowing through the conductor and the joule heat loss without using any magnetic core surrounding the current carrying path. A high thermal conductive insulating material electrically isolates the sensing device from the high voltage current carrying parts. The device reduces the iron losses to a great extent. The sensing and actuating device is used for protection purpose in the event of a sustained overload or fault condition. It reduces the temperature rise in the device by cooling the heat source during conversion of heat

energy into electrical power. The device causes actuation of the tripping mechanism at an intended current without using any external protection units.
[00108] Although the invention is described with various specific
embodiments, it will be obvious for a person skilled in the art to practice the invention with modifications. However, all such modifications are deemed to be within the scope of the claims.
[00109] It is also to be understood that the following claims are intended to
cover all of the generic and specific features of the present invention described herein and all the statements of the scope of the invention which as a matter of language might be said to fall there between.

CLAIMS
What is claimed is:
1. A current sensing and actuating device comprising;
a thermoelectric generator (TEG);
a thermocouple element coupled to the thermoelectric insulator;
a terminal connected to the thermocouple element of the TEG;
an insulator;
a conductor bonded with the TEG through the insulator;
an actuator and;
a compression spring;
Where in the device sense the current flowing through the conductor using
the thermoelectric generator and causes the actuation of the protection unit
due to magnetostriction effect of the individual layer of the composite
actuator.
2. The device according to claim 1, wherein the thermocouple element includes a plurality of a series connected N and P junction thermocouples.
3. The device according to claim 2, wherein the plurality of N and P type thermocouple elements are connected with each other by means of high electrical conductivity materials.
4. The device according to claim 3, wherein the high electrical conductivity
materials includes at least one of copper and aluminum.
5. The device according to claim 2, wherein the plurality of N and P type
thermocouple elements is selected from a group comprising of Bismuth

telluride (BiTe), lead Telluride (PbTe) and silicon germanium (SiGe) material.
6. The device according to claim 1, wherein the insulator is a thermal conductive element arranged between the current carrying conductor and the TEG.
7. The device according to claim 1, wherein the insulator is adapted to transfer the heat generated in the current carrying conductor to a hot junction of the TEG.
8. The device according to claim 1, wherein the insulator is an aluminum nitride ceramic.
9. The device according to claim 1, wherein the terminal is a silver plated copper conductor connected to the thermocouple element of the TEG.
10. The device according to claim 1, wherein one end of the compression spring is connected to at least one of the actuator and the insulator.

11. A device according to claim 1, wherein the actuator is arranged on top of the insulator.
12. The device according to claim 1, wherein the actuator is a composite material including at least three layers with different magnetostriction coefficients.

13. The device according to claim 12, wherein the composite material includes at least one of a ferromagnetic material and an alloy material bonded to each other.
14. The device according to claim 1, wherein the actuator is adapted to sense a magnetic field created by the current carrying conductor which causes the actuator lever to develop a sufficient stroke and force to operate the tripping mechanism.

15. The device according to claim 1, wherein the magnetic field generated by the current carrying conductor lifts the actuator lever to provide the sufficient stroke for tripping.
16. The device according to claim 1, wherein the TEG is adapted to maintain a lower end at an ambient temperature creating a differential temperature between a hot junction and a cold junction of TEG.
17. The device according to claim 15, wherein the differential temperature excites the electrons to flow from a P-type element to N-type element of the thermocouple to absorb the heat produced at the hot junction.
18. The device according to claim 1, wherein thermocouple elements are connected in series in rectangular array form to increase the output of the TEG.
19. The device according to claim 1, wherein the spring holds the actuator with a force sufficient to overcome three times of the weight of the spring.

20. The device according to claim 1, wherein the magnetic field creates a positive deflection in the actuator to overcome the spring force to actuate the tripping mechanism of the protection unit.