DESC:Linear Electromagnetic Operator

Field of the invention

The present invention relates to an electrical operator and more particularly, to a linear electromagnetic operator suitable for operating a manually driven switching device.

Background of the invention

Electrical operator is a device, which converts manually operated devices to a remotely operated automatic device. Broadly, it can be classified into two categories viz. a motor operator and a solenoid operator. In case of the motor operator, the torque speed characteristics are nonlinear and for the solenoid operator, it is inverse hyperbolic flat force – stroke (F-S) characteristics. Hence for a particular size of the operator, the effective power provided by either of the above mentioned operator to the switching device is very low. Also, it demands for a high stroke length of the device. The useful power transmitted by the operator can be improved by means of providing a constant force – stroke characteristics as against the nonlinear or inverse hyperbolic F-S characteristics.

Attempts have been made in the prior art to develop electromagnetic operators. For example, US Patent No. 3241006, to D.B. Products Inc, Corporation of California, discloses transducers and solenoids for converting electrical energy to linear mechanical force and has its general objective to provide a solenoid, which provides a substantially constant output force throughout its stroke. The invention provides an electromagnetic operator embodying a means for shunting magnetic flux lines across a neutral force path so as to provide a substantially constant force throughout its movement range. More specifically, the invention provides an electromagnetic operator of the solenoid type with an armature and coil arbor structure for shunting flux across a neutral force path so as to provide constant output force. The armature and coil arbor structure of the electromagnetic operator are provided with connected axial and radial air gaps which interrupt the magnetic circuit of the operator. The axial gap continues the actuating flux which provides the operating force and radial gap serves as variable flux shunting path across balance and neutral path.

However, the invention has several drawbacks like power consumption of the coil is high, power output to weight ratio is low, power output to stroke ratio is low. Also, the useful flux to drive power is very low due to shunting of the main flux path. The invention is suitable for low VA output of the actuator. The force claimed to be constant may not have a flat characteristics and hence not suitable for short travel of the actuator.

Another US Patent No. 2671863 discloses an improved control device where in the initial operating force obtained is high as compared to the standard electromagnetic device, which provides minimum starting force. The force is obtained by means of electric induction in one part and another part of the operation by magnetic attraction.

However, unlike conventional operators, though the starting force is higher, but still the F-S characteristics are not constant. Hence, power consumption of the coil is high, power output to weight ratio is low and power output to stroke ratio is low.

The US Patent File No. 2422260 describes low energy consumption electromagnetic operators and more particularly to those of iron clad single working gap type. Another US patent no. 2358828 discloses an electromagnetic operator of the series working gap type, the energy consumption of which is very small in comparison to electromagnetic operators of conventional form and capable of performing equivalent work. The improvement is due to provision of a core having at its ends enlargements forming pole faces, which are considerably greater in area than cross-sectional area of the body of the core.

The basic patent relates towards development of a solenoid operator, which does not get saturated due to increase in the flat pole face area of the plunger. This reduces the flux density below the knee point of the B – H curve. However, F-S characteristics is still not a constant characteristics, force developed by prime mover is not effectively utilized, starting force will not be high to drive the switching device against inertia of the moving system and the power output to weight and stroke ratio is low.

Another US Patent File No. 2629007 discloses electromagnetic operators and solenoids. The principle objective of the invention is to provide improved solenoid which is capable of delivering a greater force at the beginning of its stroke compared to the remainder of its stroke relative to those known in the art. The increase in the starting force is due to reduced air gap (SHADE).

However, the invention has drawbacks like though the starting force is high, the force variation over the entire travel is not constant. Power output to stroke ratio and power output to weight ratio is low and not suitable for short stroke actuator.

One more US Patent No. 2850685 relates to electromagnetic operators of the type which comprise a U shaped core and an armature rockably mounted on one of the side arms of the core and having a portion adjacent to the other side arm for attraction there towards. It is an object of this invention to provide improved and frictionless means for maintaining the armature in position relative to the core and for guiding the armature in its operative movements.

However, the invention has drawbacks like the force is not constant throughout the travel of the switching device. Rather it is an inverse – hyperbolic function. The power output to stroke or power output to weight ratio is low and not suitable for short stroke actuator.

The linear electromagnetic operator works on the Basic Lorent’z force principle which states that when a current carrying conductor is placed inside a magnetic field, it experiences a force and this force is proportional to the current applied to the coil.
From the Lorentz force equation, the force on an N turn coil of average turn length ‘L’ is
F= ?vol BINL dv

Where, F is the force developed by the operator, B is the magnetic flux density perpendicular to the coil direction and I is the current flowing through the coil. The force F is perpendicular to both B and the current direction. The vectorial representation of the three planar quantities is decided by means of the Flemming’s left hand rule.

Most of the conventional electrical operators have nonlinear force stroke characteristics and hence for a particular frame size, the effective power delivered by these operators to the basic switching device is not the same throughout the travel. In such devices, the starting force provided to the switching device is low and hence demands for higher NI so as to overcome the operating force of the switching device. In case of solenoid operator, due to increase in the NI, the core gets saturated very near to the sealing point of the electromagnet. This restricts the effective usage of the electromagnet. In order to avoid this, core and plunger area should be increased by a substantial amount. Hence, the overall dimension of the operator increases.

Accordingly, there exists a need to provide a linear electromagnetic operator with constant force stroke characteristics which overcomes the drawbacks of the
prior art.

Objects of the invention

An object of the present invention is to develop a linear electromagnetic operator with constant force stroke characteristics.

Another object of the present invention is to use an insulated former coil as a driving component for an operation of a manually operated device.

Summary of the invention

Accordingly, the present invention provides a linear electromagnetic operator for operating a manually driven switching device. The linear electromagnetic operator is mounted on the switching device. The linear electromagnetic operator comprises an electromagnet assembly, a cover assembly and a mounting plate assembly.

The electromagnet assembly includes a plurality of grooves configured at each corner thereof and a central rectangular pole face. The electromagnet assembly comprises a core, an insulated coil, a leaf spring and a permanent magnet. The insulated coil former includes a winding, an extended rectangular part resting around a periphery of the central rectangular pole face, a plurality of grooves configured at two adjacent sides thereof and a pair of cuts configured at extreme ends thereof. The extended rectangular part is extended into a rectangular shape profile. The profile on the top surface carries a self adhesive sticker/printing/flag indicator for status indication of the operation of the switching device. The leaf spring is accommodated inside the plurality of grooves of the insulated coil former. The permanent magnet is attached along four surfaces of the core for creating a radial magnetic field.

The cover assembly includes a bottom cover, an electronic module, a pair of top covers, an incoming cable, a lens, a shroud, a padlock, a key and a push to trip stud. The bottom cover includes a lower housing and an upper housing. The electronic module is accommodated partially inside the upper housing of the bottom cover. The pair of cuts configured at extreme ends of the insulated coil former carries a plurality of output terminals projecting out of the electronic module.

The pair of top covers is provided for the lower housing and the upper housing of the bottom cover. One of the top cover of the pair of top covers includes a rectangular hollow solid part. The incoming cable is used for feeding rated supply. The lens is accommodated inside a plurality of ribs configured on a front surface of the bottom cover. The lens is a convex shaped insulated material with a convex profile and a flat profile. The shroud is connected to the bottom cover through a click fit. The padlock is used for locking a knob of the switching device. The key is used for manual operation of the switching device and the linear electromagnetic operator. The push to trip stud is used for testing functioning of the switching device.

The mounting plate assembly includes an upper mounting plate, a lower mounting plate, an upper hinge plate, a lower hinge plate and a pin. The lower mounting plate and the upper mounting plate are “C” shaped steel sheets. The upper mounting plate includes a pair of rectangular slots for entry of the push to trip stud and entry of tools to set the current. The upper mounting plate is mounted on the core through the plurality of embossing configured at a bottom surface of the core. The lower mounting plate includes a first rectangular opening and a second rectangular opening. The second rectangular opening is provided for visibility of a marking upon the switching device.

The lower mounting plate includes a first set of at least four counter shank holes for mounting on the switching device and the upper mounting plate includes a second set of at least four counter shank holes for mounting the core of the operator along with the bottom cover of the cover assembly. The upper hinge plate is welded to the upper mounting plate and includes a tubular plate. The lower hinge plate is welded to the lower mounting plate and includes a tubular plate. The pin enters through the tubular plates for connecting the upper hinge plate and the lower hinge plate.

Brief description of the drawings

Figure 1 shows a sectional view of a linear electromagnetic operator in OFF state of operation of a switching device, in accordance with the present invention;

Figure 2 shows a 3D view of the linear electromagnetic operator of figure 1;

Figure 3 shows a back view of the linear electromagnetic operator of figure 1;

Figure 4 shows a bottom view of the linear electromagnetic operator of figure 1;

Figure 5 shows a side view of the linear electromagnetic operator along with the switching device in an un-mounted position, in accordance with the present invention;

Figure 6 shows a perspective view of a core of the linear electromagnetic operator of figure 1;

Figure 7 shows a side perspective view of an insulated coil former of the linear electromagnetic operator of figure 1;

Figure 8 shows a permanent magnet of the linear electromagnetic operator of figure 1;

Figure 9 shows a leaf spring of the linear electromagnetic operator of figure 1;

Figures 10a to 10c show a bottom cover of a cover assembly of the linear electromagnetic operator of figure 1;

Figure 11 shows a lens of the linear electromagnetic operator of figure 1;

Figure 12a shows a position of a PCB of an electronic module inside the bottom cover, in accordance with the present invention;

Figure 12b shows a PCB assembly of the electronic module, in accordance with the present invention;

Figure 12c shows a control circuit diagram of the electronic module, in accordance with the present invention;

Figure 12d shows an output terminal of the electronic module, in accordance with the present invention;

Figure 13 shows means of an incoming cable routing from the linear electromagnetic operator of figure 1;

Figures 14a and 14b show a pair of top covers of the cover assembly, in accordance with the present invention;

Figure 15 shows a padlock arrangement, in accordance with the present invention;

Figure 16 shows a side perspective view of a key used to operate the switching device manually, in accordance with the present invention;

Figure 17 shows a side perspective view of a push to trip stud, in accordance with the present invention;

Figure 18 shows a perspective view of a shroud, in accordance with the present invention;

Figure 19 shows a perspective view of a lower mounting plate of a mounting assembly of the linear electromagnetic operator of figure 1;

Figure 20 shows a perspective view of an upper mounting plate of the mounting assembly of the linear electromagnetic operator of figure 1;

Figures 21a and 21b show an upper hinge plate and a lower hinge plate of the mounting assembly, in accordance with the present invention;

Figure 22 shows a pin connecting the upper hinge plate and the lower hinge plate, in accordance with the present invention;

Figure 23 shows an extended extruded part of the linear electromagnetic operator of figure 1;

Figure 24 shows a perspective view of the cover assembly fitment with the core of an electromagnet assembly, in accordance with the present invention;

Figure 25 shows winding end terminations, in accordance with the present invention; and

Figure 26 shows a means of the insulated coil former feature of the linear electromagnetic operator, in accordance with the present invention.

Detailed description of the invention
The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art, techniques and approaches are overcome by the present invention as described below in the preferred embodiments.

The present invention provides a compact linear electromagnetic operator that offers excellent control characteristics where linear actuation is required over long distance. The operator develops force in either of the direction by reversing the polarity of the excitation. Applying a voltage across terminals of the operator causes the operator to move to one direction. Reversing the polarity of the applied voltage moves the operator to the opposite direction. The generated force is proportional to radial magnetic flux density, number of turns, length of turn and current that flows through a coil. This force is almost constant in a specified stroke range of the operator.

The present invention is illustrated with reference to the accompanying drawings, throughout which reference numbers indicate corresponding parts in the various figures. These reference numbers are shown in bracket in the following description.

Referring to figures 1-6, a linear electromagnetic operator (500) (hereinafter “the operator (500)”) for operating a manually driven switching device (600) (hereinafter “the switching device (600)”) in accordance with the present invention is shown. Specifically, the operator (500) is mounted on the switching device (600) such as a molded case circuit breaker as shown in figure 2.

The operator (500) comprises an electromagnet assembly (100), a cover assembly (300) and a mounting plate assembly (not numbered).

The electromagnet assembly (100) comprises a core (20), an insulated coil former (40), a leaf spring (60) and a permanent magnet (80).
The core (20) is a low to medium permeable hollow rectangular core with an open top surface. The core (20) is configured with a plurality of grooves (5) at each corner (not numbered) thereof for screw fitment and a plurality of embossing (10) at a bottom surface (not numbered). In an embodiment, the plurality of embossing (10) is a threaded embossing. The core (20) includes a central rectangular pole face (15).

The insulated coil former (40) (hereinafter “the coil (40)”) rests around a periphery of the central rectangular pole face (15). The coil (40) includes a winding (not shown), an extended rectangular part (32), a plurality of grooves (34), a pair of cuts (36) and at least four protruded parts (38). The at least four protruded parts (38) are configured at a bottom surface (not numbered) of the coil (40) for providing adequate resiliency and play.

The extended rectangular part (32) projects out from a top surface (not numbered) of the coil (40). The extended rectangular part (32) encloses and rests over the central rectangular pole face (15) of the core (20). The extended rectangular part (32) is extended into a rectangular shape profile (30) (hereinafter “the profile (30)”). The profile (30) on a bottom surface (not numbered) is configured with a slotted groove (not shown) to extend into an extruded part (not numbered) of the operator (500). The bottom surface of the profile (30) also includes an extended part (24) attached thereto to drive a knob (550) of the switching device (600). The profile (30) on a top surface (not numbered) is configured with a pair of holes (26). The profile (30) on the top surface also carries a self adhesive sticker/printing/flag indicator (28) (hereinafter “the flag indicator (28)”) for status indication of the operation of the switching device (600).

The plurality of grooves (34) is provided at two adjacent sides (not numbered) of the coil (40) to accommodate the leaf spring (60). The leaf spring (60) has two geometrical shapes, a first shape (45) is configured in such a way to get the desired snap action of the leaf spring (60) and a second shape has “L” shape bending (50) for termination of the winding of the coil (40).

The permanent magnet (80) is attached along four surfaces of the core (20). In an embodiment, the magnet (80) is a medium to high permeable sintered type alnico or rare-earth permanent magnet that creates radial magnetic field, which is cut by a current flowing through the coil (40), thus developing a force in forward or reverse direction depending upon the polarity of the supply voltage.

The cover assembly (300) comprises a bottom cover (130), a pair of top covers (140), an electronic module (150), an incoming cable (160), a lens (170), a shroud (180), a padlock (190), a key (200) and a push to trip stud (210).

The bottom cover (130) and the pair of top covers (140) are insulated. The bottom cover (130) includes a first opening (102) on a front surface (not numbered) for status indication of the switching device (600) and a second opening (104) on a back surface (not numbered) for easy entry of the knob (550) of the switching device (600). Above the front surface of the bottom cover (130), a first pair of slots (106) is provided to accommodate the shroud (180) which indicate mode of operation and a second pair of slots (108) to accommodate the push to trip stud (210) and for setting the current.

The bottom cover (130) includes a cut (110) to accommodate the padlock (190). Just beneath the front surface of the bottom cover (130), a plurality of ribs (112) is provided to accommodate the lens (170) to enlarge image of the flag indicator (28). The lens (170) is a convex shaped insulated material with a convex profile (164) and a flat profile (168). The bottom cover (130) at a top surface (not numbered) is provided with a rectangular opening (114) for easy entry of the coil (40) when in motion along with the switching device (600).

The bottom cover (130) includes a lower housing (118) and an upper housing (126). The lower housing (118) and the upper housing (126) includes an opening (not shown) at respective top surface. The lower housing (118) includes a plurality of threaded grooves (116) at each corner (not numbered) thereof for screw entry. The upper housing (126) at a one side (not numbered) is provided with a cut (120) for routing out the incoming cable (160) to the electronic module (150).

The upper housing (126) serves as an upper surface of the bottom cover (130) and includes two cut bearings (122) at adjacent sides to accommodate a plurality of output terminals (not numbered) projecting out of the electronic module (150). The upper surface (126) also includes two holes (124) for easy entry of the tool.

The bottom cover (130) accommodates the electronic module (150) therein. As shown in figures 12a and 12b, the electronic module (150) comprises a PCB (148), the plurality of output terminals, electronic components (not numbered), a microcontroller (not numbered), MOSFET driver IC (not numbered) and two pair of MOSFETS (144). The electronic components include active and passive components. The two pair of MOSFETS (144) is used for the desired functioning of the electronic module (150) such as precise operating limits of operation, restoring power to the coil (40) and supply for a stipulated period of time and back up supply in the event of power failure.

The microcontroller is programmed to perform the desired functioning of maintaining the operating limits of the operator (500) and isolating the supply to the coil (40) after desired time period. The On time of the operator (500) is maintained through the microcontroller. Figures 12b and 12c show the PCB (142) and a control circuit diagram of the operator (500).

The pair of cuts (36) configured at extreme ends (not numbered) of the coil (40) carries the plurality of output terminals projecting out of the electronic module (150). As shown in figure 12d, the plurality of output terminals of the electronic module (150) consists of a cylindrical protrusion (146) for soldering wires coming out of the electronic module (150). The electronic module (150) at a bottom end (not numbered) includes a wedge shaped protrusion (148) for attachment with the leaf spring (60) resting in the coil (40). The electronic module (150) at top surface includes a counter shank hole (149) for screw fitment with the bottom cover (130). Figure 13 shows the incoming cable (160) routing to the operator (500). Rated supply is fed to the operator (500) through the incoming cable (160).

As shown in figures 14a and 14b, the pair of top covers (140) is provided for the respective housings (118, 126) of the bottom cover (130). Each top cover (not numbered) of the pair of top covers (140) includes a plurality of holes (132) for proper fitting with the bottom cover (130). One of the top cover of the pair of top covers (140) includes a rectangular hollow solid part (136) to accommodate the padlock (190). The rectangular hollow solid part (136) includes two protruded parts (134) configured thereon to hold a restraining spring (not shown) to dampen the motion of the coil (40) at an extreme end of its motion.

The padlock (190) is used during OFF position of the switching device (600), in case inhibit operation is required. In an embodiment, a rectangular insulated padlock (190) is used (Refer figure 15). The padlock (190) includes a circular hole (182) configured at a top surface (not numbered) thereof and an engraved marking (184) of “LOCK” is being done for indication purpose. The padlock (190) also includes extended protruded parts (186) at a bottom surface (not numbered) to accommodate a helical spring (not shown) that aids in returning back the padlock (190) when not in use.

The key (200) is provided for manual operation/mode of the switching device (600) and the operator (500). The key (200) is inserted into the pair of holes (26) of the profile (30) for operating the operator (500) in the manual mode. The key (200) includes a first oblong shaped insulated part (192), a first oblong shaped insulated part (194) and a pair of projected parts (196). The pair of projected parts (196) gets inserted inside the pair of holes (26) of the profile (30) of the coil (40).

The testing of the switching device (600) is done by means of the push to trip stud (210) as shown in figure 17. The push to trip stud (210) includes a first cylindrical solid part (206) and a second cylindrical solid part (208). The first cylindrical solid part (206) includes an engraving (202) at a top surface (not numbered) thereof to indicate a test button marking as “T”. The shroud (180) is used to show the operation of the operator (500) in an auto and a manual operation/mode through engravings (174). The shroud (180) is connected to the bottom cover (130) through a click fit (178).

As shown in figure 1, the mounting plate assembly comprises a lower mounting plate (330), an upper mounting plate (350), an upper hinge plate (360), a lower hinge plate (370) and a pin (380).

In an embodiment, the mounting plates (330, 350) are “C” shaped steel sheets. As shown in figure 19, the lower mounting plate (330) includes a first set of at least four counter shank holes (310) (hereinafter “the counter shank holes (310)”), an oblong hole (312), a plurality of holes (314), a first rectangular opening (316), a second rectangular opening (318) and a pair of rectangular slots (320). The counter shank holes (310) are configured at each corner (not numbered) of the lower mounting plate (330) and adapted for mounting on the switching device (600). The oblong hole (312) is provided for accessing the power terminal of the switching device (600) through the lower hinge plate (370).

The plurality of holes (314) is provided to access other power terminals of the switching device (600) while the operator (500) is in mounting open position (Refer figure 19). The first rectangular opening (316) is configured at a centre of the lower mounting plate (330) for entry of the extended knob (550) of the switching device (600). The second rectangular opening (318) is provided for visibility of the marking upon the switching device (600). At the extreme left and right sides of the lower mounting plate (330), the pair of rectangular slots (320) are provided for entry of the push to trip stud (210) and a tool (not shown) to set the current setting.

The upper mounting plate (350) is mounted on the core (20) through the plurality of threaded embossing (10). The upper mounting plate (350) includes a second set of at least four counter shank holes (340) (hereinafter “the counter shank holes (340)”), a hole (342), a rectangular opening (344) and a pair of rectangular slots (346). The counter shank holes (340) are configured at each corner (not numbered) of the upper mounting plate (350). The counter shank holes (340) lock the upper mounting plate (350) with the core (20). The upper mounting plate (350) is adapted to mount the core (20) of the operator (500) along with the bottom cover (130) of the cover assembly (300).

The hole (342) is provided for accessibility of the screw for fitment of accessory to the bottom cover (130) through the upper hinge plate (350). The rectangular opening (344) is configured at a centre of the upper mounting plate (350) for entry of the insulated knob (550) of the switching device (600). At the extreme left and right sides of the upper mounting plate (350), the pair of rectangular slots (346) is provided for entry of the push to trip stud (210) and the tool to set the current setting.

The hinge plates (360, 370) are attached to the mounting plates (330, 350) through suitable welding process. The upper hinge plate (360) includes a central hole (354) and a tubular plate (358). The central hole (354) of the upper hinge plate (360) is used for easy access of the tool to tighten a terminal screw (not shown) of the switching device (600). The lower hinge plate (370) includes a central hole (364) and a tubular plate (368). The pin (380) is entered through the tubular plates (358, 368) to connect the respective hinge plates (360, 370).

As shown in figure 23, extended insulated parts (not numbered) of a bobbin (not shown) firmly get fitted with the knob (550) of the switching device (600). The extended insulated part is a rectangular shaped solid part with the surface through a rubber pad (81) touching surface of the knob (550) of the switching device (600).

Assembly:

Referring to figures 24-26, an assembly (not numbered) of the core (20) and the bottom cover (130) is shown. The coil (40) enters the bottom cover (130) through the rectangular opening (114) (Refer figure 10c) provided at the top surface of the bottom cover (130). The coil (40) rests upon the central rectangular pole face (15) of the core (20) with the extended rectangular part (32) firmly getting fitted into the knob (550) of the switching device (600) (Refer figure 6). The control supply terminals are fitted into the bottom cover (130) through the counter shank hole (149). As shown in figure 12d the wedge shaped protrusion (148) glides over the leaf spring (60) provided in the coil (40).

In an embodiment, the electronic module (150) can be suitably placed inside the upper housing (126) provided at the top of the bottom cover (130) or with higher VA rated operator can be placed partially external. The plurality of output terminals projecting out of the electronic module (150) is inserted between the pair of cuts (36) of the coil (40) and the leaf spring (60) thereby getting adequate contact pressure for the coil (40) termination. The leaf spring (60) is at resting position inside the coil (40). The plurality of output terminals of the electronic module (150) after engaging with the leaf spring (60) get flushed with the surface of the bottom cover (130). While in motion, the coil (40) collects the control supply from the electronic module (150) by gliding over the surface of the leaf spring (60).

The windings of the coil (40) are connected to the “L” bend end (50) of the leaf spring (60) and rest upon the pair of cuts (36) configured at the extreme ends of the coil (40). The coil (40) being the movable part of the operator (500), while moving forward or reverse gets the supply voltage via the electronic module (150). The top surface of the coil (40) is provided with the flag indicator (28) to show the status of the switching device (600). The plurality of ribs (112) of the bottom cover (130) accommodates the lens (170) that further enlarges the image of the flag indicator (28).

The core (20) is made to fit with the bottom cover (130) by means of a fastener (not shown) such as cheese head screws and then fitted with the pair of top covers (140). The entire assembly is then mounted on the upper mounting plate (350) of the mounting plate assembly. The lower mounting plate (330) and the upper mounting plate (350) are connected with respect to each other via the hinge plates (360, 370) attached to the respective mounting plates (330, 350). The lower mounting plate (330) is mounted on the switching device (600) and then after locking with the upper mounting plate (350), the operator (500) is mounted. The padlock (190) is provided for locking the knob (550) of the switching device (600). The push to trip stud (210) is provided to test the functioning of the switching device (600) even in assembled condition.

Operation:

Again referring to figures 1-26, in an operation, when external voltage is supplied to the electronic module (150), the coil (40) gets supply from the plurality of output terminals. The current flowing through the coil (40) cuts the radial flux passing due to the permanent magnet (80) attached to the opposite surface of the core (20). Force is developed in accordance to Lorentz law, which is responsible for driving the coil (40) either in forward or reverse direction depending upon the polarity of supply voltage. When the coil (40) moves, the connection between the leaf spring (60) and the plurality of output terminals of the electronic module (150) ensures continuous supply to the coil (40). The extended part (24) configured on the bottom surface of the profile (30) of the coil (40) being attached to the knob (550) of the switching device (600), operates the knob (550) to the desired state from a rest state of operation.

The operator (500) provides a constant force throughout the travel of the switching device (600) in both the forward and the reverse directions of the operation. The provision of the electronic module (150) ensures a precise control of the operator (500) motion in either of the direction. Additional extended protruded insulated parts along with variation of the coil parameters ensure the adaptability of the operator (500) for different frame size of the switching device (600). In case of field failure of the coil (40), the operator (500) ensures easy replacement of the coil (40) by means of removing the pair of top covers (140) attached thereto. The overall power consumption of the switching device (600) is quiet low as compared to other electrical operators.

The following graphical representation shows the constant force-stroke characteristics of the operator (500) in accordance with the present invention.

In an embodiment, the operator (500) is designed to operate a 125 A rated MCCB which requires a closing force of maximum 2 kg for a stroke of 22 mm. The design has been done for 24 / 48 and 110 V DC. The test results for 110 V DC are as illustrated
Pick up Voltage : - 48 – 54 V DC
Coil pick up current : - ? 0.65 A
Coil resistance : - < 92 ohm
Coil Number of turns : - 1800
Maximum VA consumption :- < 35 VA @ pick up voltage
Mechanical life completed :- 30,000 (With no wear out)

Advantages of the invention

1. The operator (500) technology is adaptable to different variants and gives precise control of the operator (500) motion.
2. The operator (500) facilitates ease of coil replacement, ease of mounting on the switching device (600) and avoids shock through restraining energy of the spring.
3. The operator (500) provides high power to stroke ratio, high power to weight ratio and constant power output.
4. The operator (500) enables auto and manual operations.
5. The coil (40) being the movable part of the operator (500) collects the supply voltage via the electronic module (150) while in motion.
6. The operator (500) facilitates ease of wiring, installation and avoids complicated mechanisms.
7. The operator (500) enables excitation of the coil (40) in short time and provide ON, Trip and OFF flag indication.
8. The operator (500) provides excellent control characteristics where linear actuation is required.
9. The operator (500) provides higher and reliable life with low intermittent power consumption.
10. The operator (500) provides a rugged and modular compact design and avoids mechanical wear and tear.

The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, and to thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient, but such omissions and substitutions are intended to cover the application or implementation without departing from the spirit or scope of the claims of the present invention.
,CLAIMS:We Claim:

1. A linear electromagnetic operator (500), the linear electromagnetic operator (500) being mounted on a switching device (600) for operation thereof, the linear electromagnetic operator (500) comprising:
an electromagnet assembly (100) having
• a core (20) having a plurality of grooves (5) configured at each corner thereof and a central rectangular pole face (15),
• an insulated coil former (40) having a winding, an extended rectangular part (32) resting around a periphery of the central rectangular pole face (15) and a plurality of grooves (34) configured at two adjacent sides thereof,
• a leaf spring (60) being capable of accommodating inside the plurality of grooves (34) of the insulated coil former (40), and
• a permanent magnet (80) attached along four surfaces of the core (20) for creating a radial magnetic field;
a cover assembly (300) having
• a bottom cover (130) having a lower housing (118) and an upper housing (126),
• an electronic module (150) being capable of accommodating partially inside the upper housing (126) of the bottom cover (130),
• a pair of top covers (140) for the lower housing (118) and the upper housing (126) of the bottom cover (130), one of the top cover of the pair of top covers (140) having a rectangular hollow solid part (136),
• an incoming cable (160) for feeding rated supply,
• a lens (170) being capable of accommodating inside a plurality of ribs (112) configured on a front surface of the bottom cover (130),
• a shroud (180) being capable of connecting to the bottom cover (130) through a click fit (178),
• a padlock (190) being capable of accommodating inside the rectangular hollow solid part (136), the padlock (190) being adapted for locking a knob (550) of the switching device (600),
• a key (200) for manual operation of the switching device (600), and
• a push to trip stud (210) for testing functioning of the switching device (600); and
a mounting plate assembly having
• an upper mounting plate (350) having a pair of rectangular slots (346), the pair of rectangular slots (346) provided for entry of the push to trip stud (210) and entry of tools to set the current,
• a lower mounting plate (330) having a first rectangular opening (316) and a second rectangular opening (318), the second rectangular opening (318) provided for visibility of a marking upon the switching device (600),
• an upper hinge plate (360) welded to the upper mounting plate (350),the upper hinge plate (360) having a tubular plate (358),
• a lower hinge plate (370) welded to the lower mounting plate (330), the lower hinge plate (370) having a tubular plate (368), and
• a pin (380) being capable of entering through the tubular plates (358, 368) for connecting the upper hinge plate (360) and the lower hinge plate (370).

2. The linear electromagnetic operator (500) as claimed in claim 1, wherein the upper mounting plate (350) is mounted on the core (20) through a plurality of embossing (10) configured at a bottom surface of the core (20).

3. The linear electromagnetic operator (500) as claimed in claim 1, wherein the insulated coil former (40) includes a pair of cuts (36) configured at extreme ends thereof to carry a plurality of output terminals projecting out of the electronic module (150).
4. The linear electromagnetic operator (500) as claimed in claim 1, wherein the extended rectangular part (32) is extended into a rectangular shape profile (30) of the insulated coil former (40), the profile (30) on a top surface carries a self adhesive sticker/printing/flag indicator (28) for status indication of the operation of the switching device (600).

5. The linear electromagnetic operator (500) as claimed in claim 1, wherein the lower mounting plate (330) and the upper mounting plate (350) are “C” shaped steel sheets.

6. The linear electromagnetic operator (500) as claimed in claim 1, wherein the lower mounting plate (330) includes a first set of at least four counter shank holes (310) for mounting on the switching device (600) and the upper mounting plate (350) includes a second set of at least four counter shank holes (340) for mounting the core (20) of the operator (500) along with the bottom cover (130) of the cover assembly (300).

7. The linear electromagnetic operator (500) as claimed in claim 1, wherein the lens (170) is a convex shaped insulated material with a convex profile (164) and a flat profile (168).