Patent Grant
8274355
The present application is based on, and claims priority from, Korean Application Number 10-2008-0138852, filed Dec. 31, 2008, the disclosure of which is incorporated by reference herein in its entirety.
The present disclosure relates to a trip device, and more particularly to a trip device applied to a molded case circuit breaker (MCCB) which provide protection of electrical circuitry from damage due to an over-current condition when an electrical failure such as overload or short-circuit occurs.
The molded case circuit breaker (MCCB) integrally housing an open/close device and a trip device in a vessel of an electrically-insulated material can open/close an electrical conductive path in response to manual or electrical manipulation, and protect an electrical circuitry from damage due to an over-current condition such as overload or a relatively high level short-circuit or fault condition by interrupting current.
In general, the MCCB refers to a circuit breaker in a molded case used for protection of an electrical circuitry of less than AC 600 volts or DC 250 volts. The MCCB is widely used to replace the conventional knife switch and fuse due to small size, easiness in manipulation and less cumbersomeness of maintenance or repair that requires replacement of fuse.
The trip device may be categorized into three types, that is, a bimetal type which carries out a trip operation by being heated and bending in response to a persistent over-current condition, an electromagnetic field type which operates by sucking a core in response to an electromagnetic field formed on a coil when an over-current flows, and an electronic type which adopts a microprocessor.
The trip characteristic is that trip activation is not operated even if a 100% rated current continuously flows but is operated for a predetermined period of time in a case when a current exceeding 125% or 150% of the rated current flows.
The present disclosure is directed to solve drawbacks of low-voltage circuit breaker and high-voltage circuit breaker and provide a multi-purpose trip device capable of improving sensitivity during interruption of over-current and obtaining reliability during interruption of short-circuited current.
In describing the present disclosure, detailed descriptions of constructions or processes known in the art may be omitted to avoid obscuring appreciation of the invention by a person of ordinary skill in the art with unnecessary detail regarding such known constructions and functions. Accordingly, the meaning of specific terms or words used in the specification and claims should not be limited to the literal or commonly employed sense, but should be construed or may be different in accordance with the intention of a user or an operator and customary usages. Therefore, the definition of the specific terms or words should be based on the contents across the specification.
In accordance with one general aspect of the present disclosure, a trip device comprises: a power source side heater connected to a power source side of a molded case circuit breaker (MCCB) to receive current; a load side heater connected to a load side of the MCCB to receive the current; and a bimetal including a direct heat unit contacting the power source side heater and an indirect heating unit facing the power source side heater, wherein the bimetal is partially fixed between the power source side heater and the load side heater and is curved when over-current or short-circuited current flows in the MCCB.
The trip device according to the present disclosure takes up both advantages of the direct heating type trip device and an indirect heating type trip device to be used as a multi-purpose trip device for both the low voltage and high voltage MCCBs.
First of all, an explanation is given to an imaginary exemplary embodiment as compared with the present invention.
In a case when sensitivity is compensated for an over-current interruption to have a distinct difference for each section of a low voltage current in a low-voltage (40 A) MCCB, a trade-off may be generated that is weak in interruption of short-circuited current having an instantaneous peak value. Meanwhile, there is a drawback in a high voltage MCCB in that the over-current interruption characteristic is not distinct for each section of current size.
The bimetal may be classified into two types based on heating method, that is, an indirect heating type and a direct heating type.
The current bypasses a bimetal 13 to directly flow to a load side terminal 15. The heating of the rotor 12 by the current applied to the power source side serves to heat the bimetal 13, and the heated bimetal 13 is thermally deformed to activate the open/close device, whereby the stator 11 and the rotor 12 are disconnected to interrupt the over-current or the short-circuited current.
The trip device of
The indirect heating type trip device may be adequate to a high voltage MCCB, because the bimetal 13 is not over-deformed over an entire area but is heated later by heat transmission to adjacent elements, compared to the direct heating type trip device that directly applies the current to the bimetal 13. However, there is a limit in applying to a low voltage MCCB requiring sensitivity to over-current interruption, due to the fact that the bimetal 13 is not sensitively thermally-deformed to a narrow variation width of rated current.
An armature 17 is instantly activated when a failure such as short-circuit is generated in a circuit to interrupt the current, where the armature 17 is therefore activated separately from the bimetal 13.
The present disclosure provides a multi-purpose trip device that is incorporated with advantages and that compensates disadvantages of the indirect and direct heating type trip devices, and the multi-purpose trip device proposed in the present disclosure takes up only the advantages of the indirect and direct heating type trip devices to thereby be applied to low-voltage MCCB and high-voltage MCCB at the same time.
The present disclosure now will be described more fully hereinafter with reference to
An MCCB according to
The open/close device 130 may include a handle 131 rotatably supported by the body 110, a latch 132 connected to the handle 131 to be changed in response to the rotation of the handle 131 and to move the rotor 150, a latch holder 133 connected to the latch 132 to restrict the operation of the latch 132, a driving pin 134 connected to the latch holder 133 to move in response to the movement of the latch holder 133, and a cross bar 135 restricting the latch holder 133.
The warning device 140 may include a micro switch 141 mounted inside the body 110 and having a contact point 144 thereunder, a switching lever 142 rotatably mounted at the body 110 to be restricted by the driving pin 134 of the open/close device 130, and a spring 143 connected to the switching lever 142 to provide a restoring force.
The open/close device 130 is released by two operations, that is, a mechanical operation and an electrical operation.
First, in case of release of the open/close device 130 by the mechanical operation, a user depresses a trip button to release the open/close device 130, or the trip device 200 is activated to release the open/close device 130, the operations of which are explained below.
In a case a restricted condition of the latch holder 133 is released by the operation of the cross bar 135 to rotate the latch holder 133, the restricted condition of the latch 132 restricted by the latch holder 133 is removed, and as a result thereof, the restriction of the rotor 150 is removed to interrupt a circuit between the power source side and the load side.
At the same time, in a case the driving pin 134 is moved by the movement of the latch holder 133, the restriction of the switching lever 142 is released. As a result, the switching lever 142 is rotated clockwise by the resilient restoring force of the spring 143 to allow a distal end of the switching lever 142 to depress the contact point of the micro switch 141, whereby the micro switch 141 sends a warning signal to the outside to indicate an interrupted condition of the circuit breaker.
The release operation of the open/close device 130 by the electrical failure such as over-current or short-circuited current is explained under.
First, the cross bar 135 is pushed and moved by a curved bimetal 230 in a case an over-current flows. The latch holder 133 supported by the cross bar 135 in response to the movement of the cross bar 135 is moved to release the restriction of the latch 132 restricted by the latch holder 133, whereby the rotor 150 is released of its restriction to interrupt the circuit between the power source side and the load side.
At the same time, the driving pin 134 is moved in response to the movement of the latch holder 133 to release the restriction of the switching lever 142, and as a result thereof, the switching lever 142 is rotated clockwise by the resilient restoring force of the spring 143 to allow a distal end of the switching lever 142 to depress the contact point of the micro switch 141, whereby the micro switch 141 sends a warning signal to the outside to indicate a tripped condition of the circuit breaker.
Meanwhile, the trip device 200 according to the present disclosure may include a power source side heater 210 connected to a power source side of the MCCB {e.g., a stator (not shown)} or to the rotor 150 to receive the electric power or a current, a load side heater 220 connected to a load side of the MCCB to transmit a current of the power source, and a bimetal 230.
The bimetal 230 is partially contacted and fixed between the power source side heater 210 and the load side heater 220 to be curved when an over-current or a short-circuited current flows in the MCCB. In a case the bimetal 230 is curved, a contact piece 232 at a distal end of the bimetal 230 pushes out the cross bar 135 to release the open/close device 130.
The bimetal 230 may include a direct heating unit (L2) that is directly contacted to the power source side heater 210 to get conducted, and an indirect heating unit (L1) disposed in opposition to the power source side heater 210. The bimetal 230 is heated at the direct heating unit (L2) by heat conduction and an ohmic resistance of the direct heating unit (L2).
The bimetal 230 and the power source side heater 210 face each other to transmit the heat by way of radiation. In this case, the bimetal 230 and the power source side heater 210 may face each other as shown in
That is to say, as shown in the exemplary embodiments of
Meanwhile, as illustrated in the exemplary embodiment of
To wrap up, the bimetal 230 and the power source side heater 210 may be mutually contacted and fixed at the direct heating unit (L2) and directly heated by the direct heating unit (L2) in the form of ohmic resistance to thereby obtain a heating effect by heat conduction. This corresponds to the function of the direct heating type device. In the meantime, an indirect heating effect may be obtained by using the indirect heating unit (L1) in the form of convection or conductive heat transmission. This corresponds to the function of the indirect heating type device.
Therefore, the trip device according to the present disclosure can take up both the advantages of the direct heating type trip device and the indirect heating type trip device, such that the trip device according to the present disclosure can be used as a multi-purpose trip device that can be used for both the low-voltage MCCB and the high voltage MCCB.
Meanwhile, the bimetal 230 of the direct heating unit (L2) is configured in such a manner that a first surface 230a is contacted and fixed by the power source side heater 210, and a second surface 230b (which is a rear surface of the first surface 230a) is contacted and fixed by the load side heater 220. Material of the first surface 230a is different from that of the second surface 230b in the bimetal 230 which is a combination of different materials.
In a case the first surface 230a is fixed by the power source side heater 210 and the load side heater 220, only one material may be heated as shown in
It is also preferable that the power source side heater 210 and the load side heater 220 be fixed to the bimetal 230 by a rivet 250. The reason of fixing by rivet 250 is to reduce or restrict the occurrence of defect of
Meanwhile, a fixed contact position of the power source side heater 210 and a fixed contact position of the load side heater 220 relative to the bimetal 230 are preferably placed at the same height when viewed in a direction the bimetal 230 is extended. Therefore, the entire area of the bimetal 230 is not affected by the occurrence of over-current which only affects the direct heating unit (L2), such that the over-current affects part of the bimetal 230 to prevent the possible defect as exemplified in
Meanwhile, a fixed contact position of the power source side heater 210 and a fixed contact position of the load side heater 220 relative to the bimetal 230 are preferably placed at different places when vertically viewed in a direction the bimetal 230 is extended, which enables formation of the riveted positions at the same height as noted above, and obtainment of heating effect by the ohmic resistance of the direct heating unit (L2) at each riveted position.
It will be appreciated that the examples disclosed herein are not to be construed as limiting of the disclosure as they are intended merely as illustrative of particular embodiments of the disclosure as enabled herein. Indeed, various modifications of the disclosure in addition to those shown and described herein will become apparent to those skilled in the art from the foregoing description and fall within the scope of the appended claims. It is therefore evident that the particular embodiments disclosed above may be all or partially altered or modified, and such features or aspects may be combined with one or more other features and/or aspects of other implementations as may be desired.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2008-0138852 | Dec 2008 | KR | national |
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