Molded-case circuit breaker for DC

The present invention relates to a molded-case circuit breaker for direct current (DC), and more particularly, to a molded-case circuit breaker for DC that contains an internal connecting conductor connecting adjacent terminals to improve insulation performance and assemblability and reduce occupied space. There is provided a molded-case circuit breaker for DC that contains a plurality of interruption units within an outer casing, the DC circuit breaker including a two-unit connecting heater that connects fixed contacts of adjacent interruption units, the two-unit connecting heater being placed within the outer casing.

CROSS-REFERENCE TO RELATED APPLICATION

Pursuant to 35 U.S.C. § 119(a), this application claims the benefit of earlier filing date and right of priority to Korean Application No. 10-2016-0184409, filed on Dec. 30, 2016, the contents of which are incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a molded-case circuit breaker for direct current (DC), and more particularly, to a molded-case circuit breaker for DC that contains an internal connecting conductor connecting adjacent terminals to improve insulation performance and assemblability and reduce occupied space.

2. Description of the Conventional Art

In general, a molded-case circuit breaker (MCCB) is an electrical device that protects a circuit and a load by automatically interrupting the circuit when there is an electrical overload or short circuit. The circuit breaker includes a terminal portion provided on the front and rear and forming a circuit connection, a mechanism divided into a fixed contact and a movable contact and mechanically opening and closing a circuit, a trip portion detecting an over-current or short-circuit current in the circuit and causing the mechanism to trip, and an extinguisher for extinguishing an arc produced when interrupting a fault current.

Such a circuit breaker is generally used for alternating current (AC) and may be converted for use in DC applications. In order to convert a circuit breaker for AC to one for DC, in the conventional art, connecting conductors (also referred to as “externally connected conductors or common bus bars”) may be added to the terminal portion of the existing circuit breaker to configure and use circuits in series.

A molded-case circuit breaker for DC according to the conventional art will now be described. A molded-case circuit breaker including an even number of poles (units) and a molded-case circuit breaker including an odd number of poles (units) will be discussed separately.

First of all, a molded-case circuit breaker with an even number of poles (e.g., four poles) will be described.

FIG. 1depicts a perspective view of a four-pole (four-unit) molded-case circuit breaker for AC according to the conventional art.FIG. 2depicts a perspective view of a four-unit molded-case circuit breaker for DC according to the conventional art.FIG. 3is an internal perspective view of the circuit breaker ofFIG. 2, from which the cover is partially cut away and the externally connected conductors are separated.FIG. 4is a perspective view of a trip portion shown inFIG. 3.FIG. 5is an exploded perspective view of tripping mechanisms, terminals, and an externally connected conductor shown inFIG. 4.FIG. 6depicts a wiring diagram of the four-unit molded-case circuit breaker for DC according to the conventional art.

As is generally known, a molded-case circuit breaker for AC according to the conventional art includes a switch mechanism3, a contact portion7, a trip portion5, and a terminal portion2a,2b,2c,2d,2e,2f,2g, and2hwhich is placed within an outer casing consisting of a case1aand a cover1b. Other internal components than the switch mechanism3are provided for each phase (unit). That is, in the four-unit circuit breaker, these components are provided for each of four phases: R phase, S phase, T phase, and N phase. The terminal portion2a,2b,2c,2d,2e,2f,2g, and2hincludes a front terminal portion2a,2b,2c, and2don the front of the circuit breaker and a rear terminal portion2e,2f,2g, and2hon the rear of the circuit breaker. For better comprehension, each unit will be described with respect to the R phase, S phase, T phase, and N phase of a circuit breaker for AC). A power source and a load may be connected to the rear terminal portion2e,2f,2g, and2h.

In order to use the circuit breaker for DC applications, externally connected conductors4aand4bare attached to the rear terminal portion2e,2f,2g, and2hand the front terminal portion2a,2b,2c, and2d.FIG. 3shows an example of a molded-case circuit breaker for DC to which the externally connected conductors are connected The front terminal portion2a,2b,2c, and2dhas a plurality of U-shaped externally connected conductors that connect a pair of adjacent terminals. In this example, an N phase front terminal2aand an R phase front terminal2bare connected by a U-shaped externally connected conductor4a, and an S phase front terminal2cand a T phase front terminal2dare connected by a U-shaped externally connected conductor4b. In the rear terminal portion2e,2f,2g, and2h, an I-shaped externally connected conductor4bmay be connected to each phase. In the terminal portion2e,2f,2g, and2hon the power source side and the front terminal portion2a,2b,2c, and2d, an insulation barrier6may be mounted between each of the externally connected conductors4aand4bin order to ensure insulation.

Referring mainly toFIGS. 3 to 5, the trip portion5includes a crossbar5bmounted across a trip portion case5a, a heater5dconnected to a fixed contact (not shown) of the contact portion7, bimetal5cthat is bent by heat generated from the heater5din case of an over-current in a circuit and that presses a contact region5b1of the crossbar5bto rotate the crossbar5b, a magnet5ethat has a magnetic force, an armateur5fthat is magnetized in case of a sudden over-current ad rotates in the direction of the magnet5e, and a trip spring5g. A tripping mechanism including the heater5d, bimetal5c, magnet5e, amarteur5f, and trip spring5gis provided for each phase. Each terminal of the front terminal portion2a,2b,2c, and2dmay be connected to the heater5d. Each terminal of the front terminal portion2a,2b,2c, and2dmay be formed integrally with the heater5d.

FIG. 5depicts a pair of tripping mechanisms, a pair of terminals, and a U-shaped externally connected conductor4aconnecting the pair of terminals. The U-shaped externally connected conductor4aserves to connect a pair of adjacent terminals. In this case, the U-shaped externally connected conductor4ais exposed out of the outer casing1aand1b.

FIG. 6shows a wiring diagram of the molded-case circuit breaker for DC according to the conventional art. The U-shaped externally connected conductor4ais attached to the front terminal portion2a,2b,2c, and2din such a manner that a pair of adjacent terminals are connected. A load8and a power source9aand9bare connected to the rear terminal portion2e,2f,2g, and2h.

Next, a molded-case circuit breaker with an odd number of poles (e.g., three poles) will be described.

FIGS. 7 and 8depict a perspective view and internal structure diagram of a three-unit molded-case circuit breaker for DC according to the conventional art.FIG. 9depicts a trip portion and a terminal.FIG. 10depicts a wiring diagram of the three-unit molded-case circuit breaker for DC according to the conventional art.

In the three-phase (three-unit) circuit breaker, three phases: R phase, S phase, T phase are provided. I-shaped externally connected conductors4bare provided at the T-phase rear terminals2f,2g, and2h(on the power source side) and the R-phase front terminal2b(on the load side). A U-shaped externally connected conductor4ais provided at the S-phase and T-phase front terminals2cand2dto connect them together. The I-shaped externally connected conductors4bare optionally mounted in order to ensure consistency with the externally connected conductor4ain terms of the arrangement of terminals or the amount of current carried. If the I-shaped externally connected conductors4bare omitted, the power source or load may be connected directly to the terminal portion2b,2c,2d,2f,2g, and2h.

When the above circuit breaker with an odd number of poles is connected in series, the input and output are not easily distinguishable in terms of position. That is, both poles9aand9bof the power source and one pole, i.e., the minus pole8bin this case, of the load are aligned in the same direction. In other words, both poles8aand8bof the load are arranged respectively on the front and rear of the outer casing1. Thus, an externally connected conductor, i.e., a connecting conductor4c, is mounted to the outside of the outer casing1(seeFIG. 10), in order to make the load terminals distinguishable from the power source terminals (for example, in order to arrange the load terminals on the front and the power source terminals on the rear) or in order to improve the assemblability of the load terminals. A cable or a bus bar may be used as the connecting conductor4c.

Since the DC circuit breaker according to the conventional art requires an U-shaped externally connected conductor4aor a connecting conductor4con the outside of the outer casing1, additional user operation is needed. Moreover, the conductive connection structure exposed out of the outer casing1may cause a possible insulation breakdown and take up more space. Additionally, even when adjacent phases (poles) are integrally connected by a U-shaped externally connected conductor, two tripping mechanisms (trip portions) still exist, and this redundancy leads to a waste of components.

SUMMARY OF THE INVENTION

The present invention has been made in an effort to solve the above-described problems, and an aspect of the present invention is to provide a molded-case circuit breaker for DC that contains an internal connecting conductor connecting adjacent terminals to improve insulation performance and assemblability and reduce occupied space.

An exemplary embodiment of the present invention provides a molded-case circuit breaker for DC that contains a plurality of interruption units within an outer casing, the DC circuit breaker including a two-unit connecting heater that connects fixed contacts of adjacent interruption units, the two-unit connecting heater being placed within the outer casing.

The two-unit connecting heater may be formed in a U-shape, and may include: a pair of head portions respectively connected to the fixed contacts of the adjacent interruption units; a pair of body portions extending downward from the head portions; and a leg portion connecting the pair of body portions.

The head portions and the leg portion may be horizontal planes, and the body portions may be vertical planes.

One of the pair of body portions may have a tripping mechanism that detects an over-current in a circuit and interrupts the circuit.

Front terminal receiving portions and rear terminal receiving portions may be provided on the front and rear of the outer casing, and insulation covers may be provided to close the front terminal receiving portions or the rear terminal receiving portions.

A trip portion case for receiving the two-unit connecting heater and the tripping mechanism may be placed within the outer casing, and a trip portion insulation cover may be provided on the front of the trip portion case.

Assembly holes may be formed in the leg portion so as to couple with the trip portion case.

The trip portion case may have a partition for insulation between the interruption units, and a cut groove may be formed on a part of the partition to insert the leg portion.

The DC circuit breaker may further include a connecting conductor, one end of which is connected to a rear terminal of an interruption unit on one side, and the other end of which is mounted in the front terminal receiving portion of the interruption unit on one side, with the connecting conductor being mounted within the outer casing.

The connecting conductor may include: a first terminal attached to the rear terminal of the interruption unit on one side; a second terminal mounted in the front terminal receiving portion of the interruption unit on one side; and a connecting portion connecting the first terminal and the second terminal.

The outer casing may include: a box-shaped case with the top and part of the front and rear being open; and a cover attached to the top of the case, wherein the case may have a first protrusion protruding from the bottom of one sidewall, the first protrusion may have a first receiving slot formed along the length, the cover may have a second protrusion protruding out from one sidewall, and the second protrusion may have a second receiving slot formed along the length to communicate with the first receiving slot, with the connecting conductor being inserted into the first and second receiving slots.

An extension may extend downward along the outer wall of the second protrusion, and the extension may have such a length at which it can adjoin the first protrusion.

The second protrusion may have the same width as the first protrusion.

A cut groove may be formed on one sidewall of the case to insert part of the connecting conductor.

According to a molded-case circuit breaker for DC according to an embodiment of the present invention, a U-shaped two-unit connecting heater is provided to connect a pair of adjacent units and therefore no front terminals and no externally connected conductors are required. Accordingly, the user does not need to add more connecting conductors, and the assemblability of the power source and load is improved.

Moreover, external insulation breakdown is prevented since a connecting conductor is configured within the outer casing. In addition, no front terminal portion is needed, thus improving insulation performance and reducing occupied space.

Further, the number of tripping mechanisms can be reduced, thus leading to a reduction in parts and production cost.

According to a molded-case circuit breaker for DC according to another embodiment of the present invention, the circuit breaker has a connecting conductor within it, the power source terminals and the load terminals are configured on the front and rear of the DC circuit breaker in an easily distinguishable manner. Thus, the user does not need to add more connecting conductors, and the assemblability of the power source and load is improved.

Moreover, external insulation breakdown is prevented since the connecting conductor is configured within the outer casing. In addition, part of the terminal portion is eliminated, thus enhancing insulation from the outside.

Further, unlike a heater provided at the R phase, a U-shaped, two-unit connecting heater is provided at the S phase and the T phase to directly connect them, and therefore the number of tripping mechanisms can be reduced, thus leading to a reduction in parts and production cost.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A molded-case circuit breaker for DC according to embodiments of the present invention will be described in detail with reference to the drawings.

A molded-case circuit breaker for DC with a plurality of interruption units according to an embodiment of the present invention includes: a two-unit connecting heater41that connects fixed contacts33bof adjacent interruption units, with the two-unit connecting heater41being placed within an outer casing of the circuit breaker.

FIGS. 11 and 12depict front and rear perspective views of a molded-case circuit breaker for DC according to an embodiment of the present invention.FIG. 13depicts a perspective view of the circuit breaker ofFIG. 11with externally connected conductors attached to it.FIG. 14is a perspective view of the circuit breaker ofFIG. 13, from which the cover is partially cut away.FIGS. 15 and 16are perspective views of a base assembly and a trip portion assembly applied to a molded-case circuit breaker for DC according to an embodiment of the present invention.

A molded-case circuit breaker for DC according to an embodiment of the present invention includes a plurality of interruption units. The interruption units correspond to interruption units applied to respective phases (poles) of a molded-case circuit breaker for AC. Therefore, for better comprehension, a four-unit molded-case circuit breaker will be described with respect to the R phase, S phase, T phase, and N phase. A DC four-unit circuit breaker10according to an embodiment of the present invention includes a case11and a cover18that constitute an outer casing, a switch mechanism30(seeFIG. 25) that provides opening and closing forces, a base assembly35provided for each phase and having a contact portion, a trip portion assembly40provided on the front of the base assembly35, and a two-unit connecting heater41.

The case11forms the bottom of the outer casing. The case11may have the approximate shape of a box with its top and part of its front and rear being open. The base assembly35is accommodated in the internal space of the case11. Since the four-unit circuit breaker has a four-unit circuit of the R phase, S phase, T phase, and N phase, it contains four base assemblies35. The case11may be divided into four segments.FIG. 11depicts an example in which the N phase, R phase, S phase, and T phase are arranged in this order from right. Front terminal receiving portions12and rear terminal receiving portions13are provided on the front and rear of the case11. The front terminal receiving portions12and the rear terminal receiving portions13provide a space where a load terminal or power source terminal can be mounted. The terminal receiving portions on either the front or rear (the front in this embodiment) remain unoccupied.

The cover18is attached to the top of the case11. The top side of the cover18is partially open, with a top cover19mounted on it. A handle31of the switch mechanism30is exposed through a hole at the center of the top cover19, thereby allowing the user to manually apply an actuating force to it.

The front terminal receiving portions12may be covered with insulation covers26. As the front terminal receiving portions12have no terminals mounted in them, they are covered with the insulation covers26, thus improving insulation performance.FIG. 14shows that some of the front terminal receiving portions12have no terminals mounted in them since the insulation covers26have been removed.

In the rear terminal receiving portions13, terminals of the respective phases are mounted and exposed. That is, an N phase terminal36a, an R phase terminal36b, an S phase terminal36c, and a T phase terminal36dare provided in terminal receiving portions of the respective phases, respectively.

FIGS. 13 and 14show that externally connected conductors20are attached to the respective terminals of the rear terminal receiving portions13. The externally connected conductors20are provided to facilitate attachment of the positive and negative terminals of a power source60aand60bor load70. The externally connected conductors20may be formed from an I-shaped flat plate.

An insulation barrier25may be provided between each externally connected conductor20. The insulation barrier25improves insulation between each phase.

The base assembly35and the trip portion assembly40will be described with reference toFIGS. 14 to 16. The base assembly35is provided for each phase. In the four-unit circuit breaker, four base assemblies35to be respectively applied to the N phase, R phase, S phase, and T phase are arranged in parallel. Each base assembly35has a contact portion within a base mold39formed from an injection-molded material. The contact portion includes fixed contacts33aand33band movable contacts34. As depicted inFIG. 15, in the case of twin contact type, the contact portion includes fixed contacts consisting of a rear fixed contact33aand a front fixed contact33band symmetrical movable contacts34. The rear fixed contact33ais connected to the terminal36a,36b,36c, or36dof each phase. The rear fixed contact33aand the terminal36a,36b,36c, or36dof each phase may be integrally formed. The terminal36a,36b,36c, or36dof each phase protrudes from one side (the rear side) of the base assembly35, and the base assembly35is exposed through the rear terminal receiving portion13when attached to the case11. Among the terminals36a,36b,36c, and36dof the respective phases, the N phase terminal36aand the T phase terminal36dmay be connected to the power source60aand60b. Also, the R phase terminal36band the S phase terminal36cmay be connected to the load70.

The movable contacts34are mounted on a shaft37and rotate with the shaft37. Each shaft37is connected by a shaft pin38and all the shafts37rotate together, thereby causing the contact portions of the four units to open and close simultaneously. The switch mechanism30is mounted on the base assembly35of a certain phase, typically, the S phase base assembly, and transfers actuating force to the shaft pin38that is attached to a part of the switch mechanism30. The operations of the movable contacts and switch mechanism30are identical to those in the conventional art, so any further detailed descriptions of them will be omitted.

The trip portion assembly40is mounted on the front of the base assembly35. The trip portion assembly40detects an over-current flow in a circuit and interrupts it, and may include a trip portion case45, a two-unit connecting heater41connected to a pair of adjacent front fixed contacts, bimetal42that can be bent by heat, a crossbar43that is rotated by the bimetal42, and a chute44that rotates when released from the crossbar43to strike a nail32of the switch mechanism30and allow the switch mechanism30to perform an off operation.

The crossbar43may have a plurality of contact regions43aand43cthat protrude to make contact with the bimetal42. Each contact region may be formed at only one of two adjacent phases. For example, the first contact region43ais provided at one of the S and T phases, and the second contact region43cis provided at one of the N and R phases. That is, no contact region may be provided at the other of the S and T phases and the other of the N and R phases.

A tripping mechanism is common to two adjacent phases. For example, a tripping mechanism may be provided for a pair of interruption units connecting the N phase and the R phase and also for a pair of interruption units connecting the S phase and the T phase.

The trip portion case45has a partition45afor insulation between each phase (unit). The partition45amay be made from a double wall to improve insulation performance. A cut groove45bmay be formed by partially cutting away the bottom of the partition45a. A leg portion41cof the two-unit connecting heater41may be inserted into the cut groove45b.

A trip portion insulation cover54is provided on the front of the trip portion case45. The trip portion insulation cover54may be formed to completely close the front of the trip portion case45. Insulation performance can be improved because the trip portion is insulated by the trip portion insulation cover54. Insulation performance can be greatly improved because the front terminal receiving portions12each have a double wall that is formed by an insulation cover26and the trip portion insulation cover54.

Referring further toFIGS. 16 to 18, the two-unit connecting heater41is provided to connect the front fixed contacts33bof a pair of adjacent front phases (e.g., the S phase and the T phase). The two-unit connecting heater41is formed in a U-shape. One end of the two-unit connecting heater41is connected to the front fixed contact33bof any one (e.g. the S phase) of the pair of adjacent phases, and the other end of the two-unit connecting heater41is connected to the front fixed contact33bof the other (e.g. the T phase) of the pair of adjacent phases. Tripping mechanism components may be provided on one side (either the S phase or the T phase) of the two-unit connecting heater41. That is, the components of the tripping mechanism, except the heater, including a fixing bracket47, a magnet48, an amarteur49, and a trip spring49a, may be provided at one (e.g., the S phase) of a pair of adjacent phases but not at the other phase (e.g., the T phase).

The two-unit connecting heater41may include a pair of head portions41aconnectable to a pair of adjacent front fixed contacts33b, a pair of body portions41bextending downward from the head portions41a, and a leg portion41cconnecting the pair of body portions41b. The head portions41aand the leg portion41cmay be horizontal planes, and the body portions41bmay be vertical planes. The body portions41bmay be partially bent so as to keep a certain distance from the tripping mechanism. Center holes41dand41emay be formed in the regions of contact between the head portions41aand the body portions41band the regions of contact between the body portions41band the leg portion41c, in order to improve strength and facilitate the formation of bends. Also, assembly holes41fmay be formed in the leg portion41cso as to couple with the trip portion.

A pair of adjacent phases (e.g., the S phase and the T phase) are connected by the two-unit connecting heater41, and it means that two phases may be covered by one heater. Moreover, the two-unit connecting heater41serves as a current-carrying path. Therefore, the two-unit connecting heater41requires no front terminals (2a,2b,2c, and2din the conventional art) (compareFIG. 1andFIG. 14and compareFIG. 4andFIG. 16).

Since a pair of adjacent phases are directly connected by the two-unit connecting heater41, a pair of adjacent terminals and an externally connected conductor connecting them are unnecessary. Thus, there are no components that are exposed out of the front terminal receiving portions12. Accordingly, insulation performance is improved.

Moreover, since the front terminal receiving portions12have no terminals within them and therefore no components are exposed externally, the front terminal receiving portions12may be covered by the insulation covers26. Accordingly, insulation performance is further improved.

In addition, the tripping mechanism41A (which collectively refers to42,46,47,48, and49) is provided on any one of a pair of adjacent phases, thus reducing the number of parts and cutting costs.

A wiring diagram of a four-unit molded-case circuit breaker for DC according to an embodiment of the present invention will be described with reference toFIG. 19.

The power source60aand60band the load70are connected to the terminals of respective phases provided on the rear of the DC circuit breaker10. For example, the plus pole60aof the power source60aand60bis connected to the T phase terminal36a, and the minus pole of the power source60aand60bis connected to the N phase terminal36bon the power source side. Also, the plus pole of the load70is connected to the S phase terminal36c, and the minus pole of the load70is connected to the R phase terminal36b.

To connect a pair of adjacent phases, the two-unit connecting heater41is attached to the pair of adjacent front fixed contacts. Since the pair of adjacent phases is connected directly by the two-unit connecting heater41, no front terminals and no externally connected conductors are required. Also, the two-unit connecting heater41is contained within the outer casing of the DC circuit breaker10, it is closed off from the outside, thus improving insulation performance.

Only one trip mechanism41A is provided for a pair of adjacent phases (units), but without a heater.

According to a molded-case circuit breaker for DC according to an embodiment of the present invention, a U-shaped two-unit connecting heater is provided to connect a pair of adjacent units and therefore no front terminals and no externally connected conductors are required. Accordingly, the user does not need to add more connecting conductors, and the assemblability of the power source and load is improved.

Moreover, external insulation breakdown is prevented since a connecting conductor is configured within the outer casing. In addition, no front terminal portion is needed, thus improving insulation performance and reducing occupied space.

Further, the number of tripping mechanisms can be reduced, thus leading to a reduction in parts and production cost.

Next, a molded-case circuit breaker with an odd number of poles (three poles) according to a second embodiment will be described. The same components as the foregoing embodiment will be denoted by the same reference numerals.

A DC circuit breaker10A according to an aspect of the present invention includes a plurality of interruption units, an outer casing with front and rear terminal receiving portions12and13for each interruption unit provided on the front and rear, and a front terminal55and rear terminals36b,36c, and36dfor respective phases provided in the front and rear terminal receiving portions12and13, with fixed contacts (not shown) of a unit on one side and an adjacent unit being connected together, and a power source60being connected to the rear terminals36cand36dof a unit on the other side and an adjacent unit. The DC circuit breaker10A includes a connecting conductor50, one end of which is connected to the rear terminal36bof the unit on one side, and the other end of which is mounted in the front terminal receiving portion12of the unit on one side, with the connecting conductor50being mounted within the outer casing, and the load70being connected to the front terminal55of the unit on the other side and the other end of the connecting conductor50.

A DC circuit breaker10A according to another aspect of the present invention includes a plurality of interruption units, an outer casing with front and rear terminal receiving portions12and13for each interruption unit provided on the front and rear, and a front terminal55and rear terminals36b,36c, and36dfor respective phases provided in the front and rear terminal receiving portions12and13, with fixed contacts (not shown) of a unit on one side and an adjacent unit being connected together, and a power source60being connected to the rear terminals36cand36dof a unit on the other side and an adjacent unit. The outer casing includes a case11A with the top, front, and rear being open, and a cover18A attached to the top of the case11A, wherein the case11A has a first protrusion15protruding from the bottom of one sidewall14, the first protrusion15has a first receiving slot16formed along the length, the cover18A has a second protrusion22protruding out from one sidewall21, and the second protrusion22has a second receiving slot23formed along the length to communicate with the first receiving slot16.

First, reference will be made with respect toFIGS. 20 to 25. This embodiment provides a circuit breaker with three interruption units. Therefore, for better comprehension, the circuit breaker will be described with respect to the R phase, S phase, and T phase. ADC three-unit circuit breaker10according to an embodiment of the present invention includes a case11A and a cover18A that constitute an outer casing, a switch mechanism30, a base assembly35provided for each phase and having a contact portion, a trip portion assembly40provided on the load side (front) of the base assembly35, and a connecting conductor50.

The case11A forms the bottom of the outer casing. The case11A may have the approximate shape of a box with its top and part of its front and rear being open. The base assembly35is contained in the internal space of the case11A. Since the three-unit circuit breaker has a three-phase circuit of the R phase, S phase, and T phase, it contains three base assemblies35. Front terminal receiving portions12and rear terminal receiving portions13are provided on the front and rear of the case11A. The front terminal receiving portions12and the rear terminal receiving portions13provide a space where a front terminal or rear terminal (a load terminal or power source terminal) can be mounted.

One sidewall (e.g., the outer wall of the R phase)14protrudes from the bottom and forms the first protrusion15. The first protrusion15may be formed longitudinally along the sidewall14. The first receiving slot16is formed along the length within the first protrusion15. The connecting conductor50may be partially inserted into the first receiving slot16.

An insertion slot17is formed on the front and rear ends of the sidewall14. The insertion slot17communicates with the front terminal receiving portion12of the R phase or the rear terminal receiving portion13of the R phase.

The cover18A is attached to the top of the case11A. The top side of the cover18A is open at the center, with a top cover19mounted to the open part. A handle31of the switch mechanism30is exposed through a hole at the center of the top cover19, thereby allowing the user to manually apply an actuating force to it. One sidewall (e.g., the outer wall of the R phase)21of the cover18A may protrude outward, thereby forming a second protrusion22. The second protrusion22has the same width as the first protrusion15of the case11A. The second protrusion22has a second receiving slot23formed within it that communicates with the first receiving slot16. The first receiving slot16may be longitudinally formed along the length of the cover18A. The connecting conductor50may be partially inserted into the first receiving slot16.

An extension24extends downward along the outer wall of the second protrusion22. The extension24may be referred to as a skirt. The extension24has such a length at which it can adjoin the first protrusion15of the case11A. The cover18A is symmetrical with respect to a vertical cross-section since the second protrusion22and the extension24are formed on one side of the cover18A.

The first protrusion15is provided on the case11A, and the second protrusion22is provided on the cover18A. Thus, the connecting conductor50is inserted and mounted into the first receiving slot16of the first protrusion15and the second receiving slot23of the second protrusion22and therefore not exposed to the outside.

The base assembly35and the trip portion assembly40will be described with reference toFIGS. 21, 25, and 26. The base assembly35is provided for each phase. In the three-unit circuit breaker, three base assemblies35to be respectively applied to the R phase, S phase, and T phase are arranged in parallel. Each base assembly35has a contact portion within it. The contact portion includes fixed contacts and movable contacts. The rear fixed contact extends to form the rear terminal36b,36c, or36dof the R, S, or T phase. The rear terminal36b,36c, and36dof each phase protrudes from one side of the base assembly35. Among the rear terminals36b,36c, and36dof the respective phases, the S phase terminal36cand the T phase terminal36dmay be exposed through the rear terminal receiving portions13and connected to the power source60.

The movable contacts34are mounted on a shaft37and rotate with the shaft37. Each shaft37is connected by a shaft pin38mounted to pass through the three phases and all the shafts37rotate together, thereby causing the contact portions of the three units to open and close simultaneously. The switch mechanism30is mounted on the base assembly35of a certain phase, typically, the S phase base assembly, and transfers actuating force to the shaft pin38that is attached to a part of the switch mechanism30. The operations of the movable contacts and switch mechanism30are identical to those in the conventional art, so any further detailed descriptions of them will be omitted.

The trip portion assembly40is mounted on the load side of the base assembly35. The trip portion assembly40interrupts an over-current flow in a circuit, and may include heaters41and46connected to fixed contacts on the load side, bimetal42that can be bent by heat, a crossbar43that is rotated by the bimetal42, and a chute44that rotates when released from the crossbar43to strike a nail32of the switch mechanism30and allow the switch mechanism30to perform an off operation. In this case, the T-phase trip mechanism may be identical to the conventional trip mechanism. That is, the heater46and bimetal42of the T phase trip mechanism may be identical to the heater and bimetal according to the conventional art (seeFIGS. 9 and 26). Moreover, the T phase front terminal (load terminal)45may be connected to the heater41and exposed through the front terminal receiving portions12. In some embodiments, the T phase front terminal55may be formed integrally with the heater46.

The crossbar43has a plurality of contact regions43aand43cthat protrude to make contact with the bimetal42. The contact regions may be formed at two phases. For example, the first contact region43ais provided at the T phase, and the second contact region43cis provided at the R phase or the S phase. That is, no contact region may be provided at one of the R and S phases.

Referring further toFIG. 28, the R phase and the S phase may have a single, common tripping mechanism. A two-unit connecting heater41connecting the R phase and the S phase is provided.

The S phase and the T phase are connected by the two-unit connecting heater41, and it means that the two phases may be covered by one heater. Moreover, the two-unit connecting heater41serves as a current-carrying path. Since the R phase and the S phase are directly connected by the two-unit connecting heater41, the two-unit connecting heater41has no terminals on the load side. Referring toFIG. 26, it is depicted that the trip portion assembly40has a load terminal55only at the T phase but no load terminals at the R and S phases.

Referring further toFIG. 27, a connecting conductor50is provided to connect the rear terminal (R phase terminal in this embodiment) at one of the two phases to a front terminal receiving portion. The connecting conductor50may include a first terminal51attached to the R phase terminal36b, a second terminal52mounted in the R phase front terminal receiving portion12, and a connecting portion53connecting the first terminal51and the second terminal52. In this case, the first terminal51and the second terminal52are formed in parallel with the R phase terminal36b, and the connecting portion53is formed perpendicular to the first terminal51and the second terminal52. Accordingly, the expanded volume of the second protrusion22may be reduced to a minimum, thereby allowing for a compact circuit breaker design.

Although not listed and depicted separately herein, the connecting conductor50may exist in various embodiments. The connecting conductor50may be formed in various shapes and placed at appropriate positions within a range in which it comes with a compact design to be contained in the DC circuit breaker10. For example, the connecting conductor50may be placed in a slot formed at the bottom of the case11A.

The first terminal51is attached with a screw to the R phase terminal36b. The second terminal52is inserted and mounted into the R phase front terminal receiving portion12through the insertion slot17on the sidewall14of the case11A. The second terminal52serves as the R phase front terminal (load terminal). The connecting portion53is received in the first receiving slot16of the first protrusion15and the second receiving slot23of the second protrusion22.

Since the connecting conductor50is contained and mounted within the outer casing, i.e., the case11A and the cover18A, of the DC circuit breaker10, it is not exposed to the outside, thereby improving insulation performance. Moreover, the presence of the connecting conductor50allows for configuring the power source terminals and the load terminals on the front and rear of the DC circuit breaker, respectively, thus making it easy to recognize and use them. That is, a power source connecting terminal portion and a load connecting terminal portion are clearly and distinctively recognizable, and it is easy to connect a load without having to add an externally connected conductor, thereby improving assemblability.

Meanwhile, due to the presence of the two-unit connecting heater41, an externally connected conductor for connecting load terminals of the R and S phases is unnecessary, and the number of components exposed out of the front terminal receiving portions12is reduced. This contributes to improvement in insulation performance.

Referring toFIG. 20, an externally connected conductor20may be attached to terminals connected to a power source (the S phase- and T phase rear terminals36cand36din this embodiment) and terminals connected to a load (the T phase front terminal55and the second terminal52in this embodiment). The externally connected conductor20is exposed out of the rear terminal receiving portions13or the front terminal receiving portions12, thus providing convenience to the user.

Referring toFIGS. 20 to 22, insulation covers26may be provided at the R phase rear terminal receiving portion13and S phase front terminal receiving portion12where no externally connected conductor20is provided. Because of the insulation covers26at the R phase rear terminal receiving portion13and S phase front terminal receiving portion12, insulation performance is improved.

Moreover, an insulation barrier25may be provided between the R phase and the S phase, thereby ensuring the insulation between the phases.

Referring toFIG. 29, a wiring diagram of a three-unit molded case circuit breaker for DC according to an embodiment of the present invention will be described.

The power source60is connected to terminals on the rear of the DC circuit breaker10A. The power source60is connected to the rear terminals of two phases (units) located on the other side of the DC circuit breaker10A which are farthest from the phase (unit) where the connecting conductor50is provided.

In this embodiment, the plus pole of the power source60is connected to the T phase rear terminal36d, and the minus pole of the power source60is connected to the S phase rear terminal36c.

The load70is connected to front terminal (load terminal) on the front of the DC circuit breaker10A. The load70is connected to the load terminals of two phases (units) located on both sides of the DC circuit breaker10A. In this embodiment, the plus pole of the load70is connected to the T phase front terminal55, and the minus pole of the load70is connected to the R phase front terminal, i.e., the second terminal52of the connecting conductor50.

An externally connected conductor20may be provided at the terminals connected to the power source and load. The externally connected conductor20is for providing assemblability to the user and regulating the amount of current carried, and may be optionally used.

Since the connecting conductor50and the two-unit connecting heater41are contained in the DC circuit breaker10, insulation performance is greatly improved. The tripping mechanism41A (which collectively refers to42,46,47,48, and49), except the heater, may be provided at one of the two phases connected to the two-unit connecting heater41. That is, no tripping mechanism is provided at one of the R and S phases.

The R phase- and S phase terminals are eliminated from the front terminals (load terminals). The second terminal52of the connecting conductor50is substituted for the R phase terminal.

While this embodiment has been described with respect to a three-phase (three-unit) molded case circuit breaker for DC, it is needless to say that the present invention may be applied to a DC circuit breaker with an odd number of phases (units) more than or equal to three phases (units). In this case, it should be noted that the power source (or load) is connected to two adjacent rear terminals on one side, and the load (or power source) is connected to two front terminals on both sides (one of which that is located on the other side is the second terminal of the connecting conductor). For the other terminals, a two-unit connecting heater is used between adjacent terminals.

According to a molded-case circuit breaker for DC according to an embodiment of the present invention, the circuit breaker has a connecting conductor within it, the power source terminals and the load terminals are configured on the front and rear of the DC circuit breaker in an easily distinguishable manner. Thus, the user does not need to add more connecting conductors, and the assemblability of the power source and load is improved.

Moreover, external insulation breakdown is prevented since the connecting conductor is configured within the outer casing. In addition, part of the terminal portion is eliminated, thus enhancing insulation from the outside.

Further, unlike the heater provided at the T phase, a U-shaped, two-unit connecting heater is provided at the R phase and the S phase to directly connect them, and therefore the number of tripping mechanisms can be reduced, thus leading to a reduction in parts and production cost.