A RESIDUAL CURRENT CIRCUIT BREAKER
FIELD OF INVENTION
The present disclosure relates, in general, to a circuit breaker which provides residual current protection with or without integral over current protection, functionally dependent on line voltage for household and similar uses.
More particularly, the present disclosure relates to a microcontroller based residual current circuit breaker for providing protection against electric shock and electrical fire. The present circuit breaker may follow any desired inverse time-current characteristics for residual or earth leakage fault current protection.
BACKGROUND:
Presently, there are two kinds of Residual current operated devices, herein after called RCDs. One is electromechanically operated and other is electronically operated RCDs.
In existing electromechanically operated RCDs, residual current protection is provided by electrical means i.e. by using a current transformer and a permanent magnet relay. The protection provided by this means is not precise and also easily effected by environmental changes like humidity or change in temperature, as it totally depends upon the magnetic property of the relay used.
In electronically operated RCDs, residual current protection is achieved by using comparators circuitry or by using microcontrollers. In comparator based design, it is very difficult to achieve exact inverse time-current characteristics because time delay is provided by using the combination of passive components. This is one of the limitation of comparator based design, which is easily overcome by using microcontroller. Microcontroller is a programming device and it's easy to achieve any desired time-current characteristics by editing the program.
WO 2009/005374 relates to residual current devices (RCD's), also known as residual current circuit breakers (RCCB's), ground fault circuit interrupters (GFCFs) or appliance leakage current interrupters (ALCFs). It emphasizes on the mechanical design of the invention. When the RCD is instructed with the sensitivity level, the microcontroller sets the threshold for fault current inside the internal memory. When current imbalance between phase and neutral lines is detected during normal operation, the microcontroller will only send a signal to the SCR if the current imbalance is above the threshold set in memory. However, in the present disclosure a single threshold value is not stored in microcontroller, instead of that a whole lookup table is stored, which follows inverse time-current characteristics. The input of the microcontroller is compared against a lookup table rather than of one or two threshold values.
US patent 7079,365 provides a microcontroller-based system for detecting ground-fault and grounded-neutral conditions in a monitored circuit of an electrical power distribution system. However, the patent does not contain any test button circuitry.. US patent uses an operational amplifier to gain the sensing circuitry output, but in present disclosure no such operational amplifier is used.
US patent 7,193,827 is the modified version of the US patent 7,079,365. Only modification is that it includes a test button circuitry. According to this patent test button circuitry simply comprises a resistance between the line and neutral to produce desired fault. However, in the present disclosure the circuit is improved and totally different.
US patent 6,621,672 is about bulky circuit breakers rating greater than 63A. Basically, the US patent relates to industrial product, whereas present disclosure relates to domestic products or small size circuit breaker having current rating equal to or less than 63 A.
OBJECTS OF THE INVENTION:
The object of the present disclosure is to provide microcontroller based residual current circuit breaker with or without integral over current protection that saves life by giving protection against electric shock and fire
Yet another object of the present disclosure is to provide a remote trip residual current operated circuit breaker.
Yet another object of the present disclosure is to provide a residual current operated circuit breaker with multiple residual current rating adjuster.
Yet another object of the present disclosure is to provide a residual current operated circuit breaker which detects both residual current AC faults and pulsating DC faults and also comprises a selector switch to decide the functionality of the device as General type or S type (Delay type).
Yet another object of the present disclosure is to provide a residual current operated circuit breaker which trips under leakage current even in the case of supply neutral loss.
At the outset of the description that follows, it is to be understood that the ensuing description only illustrates a particular form of this invention. However, such a particular form is only an exemplary embodiment and is not intended to be taken restrictively to imply any limitation on the scope of the present invention.
SUMMARY AND STATEMENT OF INVENTION
According to this disclosure, a protective device is provided to protect the system against residual current faults and shows repeatability in terms of tripping at the same preset level with the use of an Electronic circuitry and microcontroller based program to give the flexibility of setting residual current levels along with the setting of the device functionality as delay type or without delay type and this can be incorporated in the device with integral overcurrent protection.
The present disclosure provides protection against AC current leakage and pulsating DC current leakage.
The present disclosure relates to residual current devices, earth leakage current devices, ground fault current interrupter and all other same devices which give protection against any residual or leakage current.
The present disclosure is based on the principle that "What amount of current flow goes in must also come out" that means the vector sum of the instantaneous value of current following in the main circuit is equal to zero (expressed in r.m.s. value).
The present disclosure teaches a residual current operated circuit breaker with or without integral over current protection. When the invention is coupled to a circuit breaker module then it's called a residual current operated circuit breaker with integral over current protection. When the invention is used without a circuit breaker module then it's called residual current operated circuit breaker or in some countries called by name earth leakage circuit breaker. The invention can also be used in socket residual current operated devices.
Accordingly, the present disclosure provides a residual current circuit breaker with or without integral over current protection against AC current leakage and pulsating DC current leakage, comprising:
regulated power supply unit for supplying regulated power to the circuit
breaker;
current sensor unit comprising a current transformer and multiple residual
current rating adjuster for sensing the leakage current and producing an output
voltage across the residual current rating adjuster;
microcontroller connected between the power supply unit and the current
sensor unit, configured to monitor the ADC input from the current sensor unit
and comprising means for generating an output signal if the ADC input
exceeds from a predefined threshold limit;
tripping unit receiving the output signal from the microcontroller;
actuating unit connected to the tripping unit which actuates the protective
device and interrupts the power supply to the load
The current sensing unit is further connected to:
test button unit for testing the normal functioning of the breaker at user end,
and/or
remote trip unit for tripping the breaker from remote location
The present circuit breaker comprises the circuit in single or multiple of miniature circuit breaker modules.
The disclosure also provides a method for providing protection against AC current leakage and pulsating DC current leakage comprising the steps of:
comparing the current flowing both in the Active and Neutral conductors of
the electrical circuit through current sensing unit;
adjusting the residual current rating through a multiple residual current rating
adjuster provided in the current sensing unit;
feeding the ADC input to the microcontroller through current sensing unit,
sensing the leakage current in case the ADC input exceeds from a predefined
threshold limit,
generating an output signal from the microcontroller to the tripping unit,
actuating the protective device through actuating unit connected to the
tripping unit, thereby interrupting the power supply to the load
BRIEF DESCRIPTION OF DRAWINGS:
Further objects and advantages of this invention will be more apparent from the ensuing description when read in conjunction with the accompanying figures and wherein:
It is to be noted, however, that the appended drawing illustrates only typical embodiment of this invention and are therefore not to be considered for limiting of its scope, for the invention may admit to other equally effective embodiments.
FIG. 1 shows the block diagram of a residual current circuit breaker, according to the present disclosure.
FIG. 2 shows the circuit diagram of the residual current circuit breaker, according to the present disclosure.
DETAILED DESCRIPTION OF THE INVENTION
Referring to Figures 1 and 2, it illustrates the preferred embodiment of the present invention.
The present disclosure provides microcontroller based residual current circuit breaker with or without integral over current protection that saves life by giving protection against electric shock and fire. Accordingly, in the present disclosure an electronic circuitry is used for residual current protection.
The current sensing unit 106, comprises a current transformer 1 for continuously comparing the current flowing both in the Active and Neutral conductors of the electrical circuit. If the current flow becomes unbalanced, it leads to current leaking to the earth, as some of the current in the Active conductor is not returning back through the Neutral conductor. The current transformer 1 senses this leakage current and produces an output voltage across the burden resistance 23 placed in parallel with the current transformer. The current transformer is capable to sense both AC and pulsating DC leakages. When there is no current unbalance i.e. the vector sum of the current values following through the active and the neutral conductor is zero then there is no voltage drop across the burden resistance 23 of the current transformer 1.
The said burden resistance 23 is actually a variable multi step resistance. By varying its steps user can adjust the defined rating of the residual current (likewise 10mA, 30mA, 100mA, 300mA, 500mA) according to requirement.
The power supply circuit 101 is electrically connected to the current path at the line side. The power supply unit 101 comprises a rectifier 102 that converts AC input signal into full wave DC output signal which is drop down by using a drop down resistance. The drop down DC
voltage is then filtered and fed to a regulator 103. The regulated output is then fed to the VDD of a microcontroller 25 which is positioned within the current path and contains an embedded software program with appropriate code to generate the required tripping pulse . Microcontroller 25 gets ADC input from the current sensing unit 106. The output of the current sensing unit is fed to the ADC channel 1 of the microcontroller by using a low dropout regulator 18 a positive reference is maintained on the ADC channel 1. Microcontroller 25 senses ADC signals and makes decision accordingly. So the microcontroller 25 receives the power from the regulated power supply 101, and ADC signal from the current sensing unit 106 and monitors it. A whole lookup table is stored in the microcontroller, which follows inverse time-current characteristics. The input of the microcontroller is compared against a lookup table rather than of one or two threshold values. When the received ADC signal exceeds from a predefined threshold limit, then the microcontroller 25 generates an output signal after a certain time interval, which trips the protective device 111 and opens the electric circuit. The output of the controller is fed into a tripping unit 109 comprising a switching device 29 which by using an actuating unit 110 comprising a solenoid 31 actuates the device 111 and interrupts the power supply to the load.
The circuit comprises a selector switch 20 to decide the functionality of the device as General type or S type (Delay type), the output of selector switch 20 is fed to the ADC channel 2 of the microcontroller 25. This selection is also user defined.
The remote trip unit 105 and test button unit 104 is intelligently designed by placing a test resistance and two parallel test buttons (denoted in circuit diagram by Test Button 32 and Remote Trip 33) in series with the test button primary winding 3 of the current transformer. The test button unit 104 is used to test the normal functioning of the breaker at consumer end and the remote trip unit 105 is used to trip the breaker from remote location.
It is to be noted that the present invention is susceptible to modifications, adaptations and changes by those skilled in the art. Such variant embodiments employing the concepts and features of this invention are intended to be within the scope of the present invention, which is further set forth under the following claims.

We claim:
1. A residual current circuit breaker with or without integral over current protection
against AC current leakage and pulsating DC current leakage, comprising:
regulated power supply unit for supplying regulated power to the circuit
breaker;
current sensor unit comprising a current transformer and multiple residual
current rating adjuster for sensing the leakage current and producing an output
voltage across the residual current rating adjuster;
microcontroller connected between the power supply unit and the current
sensor unit, configured to monitor the ADC input from the current sensor unit
and comprising means for generating an output signal if the ADC input
exceeds from a predefined threshold limit;
tripping unit receiving the output signal from the microcontroller;
actuating unit connected to the tripping unit which actuates the protective
device and interrupts the power supply to the load.
2. The residual current circuit breaker as claimed in claim 1, wherein the current sensing
unit is further connected to:
test button unit for testing the normal functioning of the breaker at user end;
and/or
remote trip unit for tripping the breaker from remote location
3. The residual current circuit breaker as claimed in claim 1, wherein the multiple residual current rating adjuster is variable multi step burden resistance allowing the user to adjust the defined rating of the residual current.
4. The residual current circuit breaker as claimed in claim 1, wherein the tripping unit comprises a switching device which by using an actuating unit actuates the protective device and interrupts the power supply to the load.
5. The residual current circuit breaker as claimed in claim 1, wherein the actuating unit comprises a solenoid.
6. The residual current circuit breaker as claimed in claim 2, wherein the remote trip unit and test button unit comprises a test resistance and two parallel test buttons in series with the test button primary winding of the current transformer.
7. The circuit breaker as claimed in preceding claims comprising a selector switch to decide the functionality of the device as General type or S type (Delay type).
8. The circuit breaker as claimed in preceding claims comprising a functional earth which provides normal functioning of the breaker in case of supply neutral loss and provides protection in case of leakage current fault.
9. The circuit breaker as claimed in claim 1 comprising the circuit in single or multiple of miniature circuit breaker modules.
10. A method for providing protection against AC current leakage and pulsating DC current leakage comprising the steps of:
comparing the current flowing both in the Active and Neutral conductors of
the electrical circuit through current sensing unit;
adjusting the residual current rating through a multiple residual current rating
adjuster provided in the current sensing unit;
feeding the ADC input to the microcontroller through current sensing unit,
sensing the leakage current in case the ADC input exceeds from a predefined
threshold limit,
generating an output signal from the microcontroller to the tripping unit,
actuating the protective device through actuating unit connected to the
tripping unit, thereby interrupting the power supply to the load.
11. A residual current circuit breaker with or without integral over current protection
against AC current leakage and pulsating DC current leakage substantially as herein
described with reference to and as illustrated in the accompanying drawings.
12. A method for providing protection against AC current leakage and pulsating DC current leakage substantially as herein described with reference to and as illustrated in the accompanying drawings.