JPH04236180A - Short-circuiting device for ac circuit - Google Patents

Abstract

PURPOSE:To simplify wirings for connecting terminals of electromagnetic contactors in a device for short-circuiting star points of an AC circuit of a delta short-circuiting system by using the contactors. CONSTITUTION:Terminals adjacent at opposite sides of contacts (s) of an electromagnetic contactor S, i.e., terminal Nos. 2-4 and 3-5 of two of three phases in main circuits R, S, T of the contactor S shown in a lower Figure such as R-S and S-T are connected by wirings A1 and A2, and the residual T-R are connected terminal Nos. 6-1 by a crossover wiring B, thereby realizing a delta short-circuiting system of a star point SP as shown in an upper Figure. Thus, only one crossover wiring B is used to simplify the wirings.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention relates to an AC circuit shorting device mainly used for starting a three-phase induction motor, and more specifically to a device for shorting the star point of a three-phase AC circuit using a delta short circuit method using an electromagnetic contactor. Regarding.

0002

[Prior Art] Some magnetic contactors are used to control the operation of three-phase induction motors such as squirrel-cage induction motors and wound-wound induction motors, which short-circuit the star point of an AC circuit. There are star short circuit method and delta short circuit method. This will be explained below using a star-delta starter as an example.

A star-delta type starter is widely used to smoothly start a three-phase squirrel cage induction motor, and FIG. 4 shows its connection diagram. In Fig. 4, three-phase alternating current supplied from power supplies R, S, and T via molded circuit breakers CB is applied to squirrel cage motor M by closing circuit of power supply magnetic contactor MC, but at startup, star magnetic contactor The electromagnetic contactor S for delta is closed and the delta electromagnetic contactor D is opened to put the stator winding of the motor in a star connection state, suppressing the starting voltage and smoothing the starting. Thereafter, when the electric motor M is accelerated to a predetermined speed, the electromagnetic contactor S is opened and then the electromagnetic contactor D is closed, the windings are switched to the delta connection state, and the supply voltage is directly applied to the windings.

[0004] In such a starter, as a method of short-circuiting the star point SP shown in the figure with an electromagnetic contactor S, (A
) and the delta short circuit method (B). The current flowing through the contacts of the magnetic contactor S is IS /√3 in the delta short circuit method compared to IS in the star short circuit method, so the delta short circuit method uses a smaller magnetic contactor S than the star short circuit method. It has the advantage of being possible.

FIG. 5 is a wiring diagram showing the connection between the terminals of the electromagnetic contactor S, and (A) shows the case of the star short circuit method, and (
B) is the case of the delta short circuit method. Numbers in the figure indicate terminal numbers. As shown in the figure, in the star short circuit method of (A), adjacent terminal numbers 2-4 and 4-6 may be connected using electric wires A1 and A2, respectively. On the other hand, in the delta short circuit method of (B), it is necessary to straddle contact s and connect terminal numbers 2-3, 4-5, and 6-1 with crossover wires B1, B2, and B3, respectively. . That is, the delta short circuit method requires more complicated wiring than the star short circuit method.

[0006]

[Problem to be Solved by the Invention] As stated above, when trying to short-circuit a star point using an electromagnetic contactor, if the delta short-circuit method is adopted, the current of the electromagnetic contactor will be lower than that of the star short-circuit method. Although the capacitance is reduced to 1/√3, a problem arises in that the wiring between the terminals of the electromagnetic contactor becomes complicated. The present invention is an attempt to solve these problems, and aims to provide an AC circuit shorting device that employs a delta shorting method for shorting star points and that simplifies wiring. .

[0007]

[Means for Solving the Problems] The present invention provides an AC circuit shorting device for short-circuiting star points of a three-phase AC circuit using a delta short circuit method using an electromagnetic contactor. For two of these, wiring is simplified by connecting adjacent terminals on opposite sides of the contacts of this electromagnetic contactor. The short circuit device described above can be applied to a star-delta starter or a Condorpha starter for a squirrel-cage induction motor, as well as a secondary resistance starter for a wound induction motor.

[0008]

[Operation] Wiring is simplified because two of the three phases can be wired between adjacent terminals.

[0009]

[Embodiment] Fig. 1 shows an embodiment of the present invention in a star-delta starter, (A) is a connection diagram of the main parts, and (B)
is a wiring diagram of the electromagnetic contactor part. In Fig. 1(B), among the three phases R-S, S-T, and T-R in the main circuit R, S, and T of the electromagnetic contactor S, the terminal number 2-4 between R and S is It is connected with wiring A1, and between ST and T, terminal number 3- is connected on the opposite side of contact s with respect to wiring A1.
5 is connected by a wiring A2, and the remaining terminals T and R are connected by a crossover wiring B between terminals 6 and 1 across the contact s. Terminal numbers 1, 2, and 3 are connected to stator winding terminals X, Y, and Z of electric motor M, respectively.

[0010] With such a connection, as shown in FIG. 1(A), a delta short circuit type short circuit in which a contact s is inserted between each phase at the star point SP is realized. According to such a connection, two of the three wires A1, A2, B connecting between the terminals of the electromagnetic contactor S are connected between adjacent terminals, and the contact point s
Since there is only one crossover wiring B that spans the area, the wiring is simpler than in the conventional example shown in FIG. 5(B).

FIGS. 2 and 3 show an embodiment in which the short circuit device of the present invention is applied to another starter for a three-phase induction motor. FIG. 2 shows an example of a Condorfer starter, in which an autotransformer T for starting a squirrel cage induction motor M is short-circuited using an electromagnetic contactor S. Furthermore, Fig. 3 is an example of a secondary resistance short-circuit starter, in which starting resistors R1 and R2 inserted on the secondary side of a wound wire induction motor are successively short-circuited using electromagnetic contactors S1 and S2. .

0012

[Effects of the Invention] According to the present invention, even in the delta shorting method, only one crossover wiring is required, so a shorting device of the delta shorting method can be configured with simple wiring while taking advantage of the small current capacity of the magnetic contactor. can do.

[Brief explanation of the drawing]

FIG. 1 (A) is a main part connection diagram showing an embodiment of the present invention;
(B) is a wiring diagram of the electromagnetic contactor portion.

FIG. 2 is a connection diagram showing another embodiment of the invention.

FIG. 3 is a connection diagram showing still another embodiment of the invention.

[Figure 4] (A) is a connection diagram explaining the star short circuit method;
B) is a main part connection diagram explaining the delta short circuit system.

[Figure 5] (A) is a wiring diagram of a star short circuit type short circuit device,
(B) is a wiring diagram of a conventional delta shorting type shorting device.

[Explanation of symbols]

M Three-phase induction motor S Magnetic contactor SP Star Point

Claims (4)

[Claims] Claim 1: A shorting device for an AC circuit that shorts star points of a three-phase AC circuit using a delta short circuit method using a magnetic contactor, in which two of the three phases in the main circuit of the magnetic contactor are short-circuited. A short circuit device for an alternating current circuit, characterized in that adjacent terminals on opposite sides of the contacts of an electromagnetic contactor are connected to each other. 2. A star-delta starter for a three-phase induction motor, characterized in that the device according to claim 1 is used. 3. A Condorpha starter for a three-phase induction motor, characterized in that the device according to claim 1 is used. 4. A secondary resistance starter for a three-phase induction motor, characterized in that the device according to claim 1 is used.