JPH0589754A - Static switch - Google Patents

Abstract

PURPOSE:To enhance safety to electric shock, and simultaneously realize the suppressing of temperature rise of a semiconductor switching element and the miniaturization of the whole body. CONSTITUTION:Between each pair of power source side terminals R, S, T and load side terminals U, V, W, a parallel circuit of thyristor 13, 14 connected in reverse parallel and a serge absorbing circuit 15, and a parallel circuit of thyristor 16, 17 connected in reverse parallel and a serge absorbing circuit 18 are connected, respectively, and relay contacts 11a, 11b, 11c are interposed in each current carrying path through them. An input circuit part 20 immediately turns on the relay contacts 11a-11c when an external operating signal is inputted and turns on the thyristors 13, 14, 16, 17 after the lapse of a determined delay time. When the input of the external operating signal is stopped, the thyristors 13, 14, 16, 17 are immediately off, and the relay contacts 11a-11c are off after the lapse of the delay time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a static switch in which a load circuit is opened and closed by a semiconductor switching element.

[0002]

2. Description of the Related Art Conventionally, a large number of electromagnetic contactors have been used for opening and closing a circuit that uses a motor as a load. It is becoming more common to use static switches that use semiconductor switching devices. That is, it is considered useful to use a static switch that can be expected to have a long service life without contact wear, for devices such as an overhead crane and a hoist that frequently perform inching operation of an electric motor.

FIG. 3 shows a circuit configuration of essential parts in a conventional three-phase static switch. In FIG. 3, the main circuit unit 1 includes power source side terminals R, S, T and load side terminals U, V, W.
And a power absorbing thyristor 2, 3 which is a semiconductor switching element, are connected in anti-parallel between each pair and a surge absorbing circuit 4 including a non-linear resistance element 4a, a capacitor 4b and a resistance 4c. .. In this case, a trigger signal is applied to the gates of the thyristors 2 and 3 of each phase according to the input of the external operation signal. Therefore, the main circuit unit 1 is turned on in the state where the external operation signal is input and exhibits a closed state in which the terminals R, S, T and the terminals U, V, W are electrically connected to each other, and the external operation signal Is turned off in the state of inputting, and an open circuit state in which the terminals R, S, T and the pairs of terminals U, V, W are cut off is exhibited.

[0004]

One of the drawbacks of the static switch having the above construction is a safety problem. That is, in the main circuit portion 1, even if the main circuit portion 1 is in the open circuit state, a leakage current flows through the surge absorbing circuit 4, so that the voltage is constantly applied to the ground side (load side terminals U, V, W side).
Therefore, for example, when the static switch is used for controlling the electric motor, even if the main circuit unit 1 is switched to the open circuit state, a certain amount of voltage is applied to the electric motor side due to the reason described above.

Therefore, at the time of start-up inspection of the device using the electric motor as a drive source, even if the main circuit portion 1 is switched to the open state, an electric shock accident may occur at the time of inspection of the electric motor. Electric shock current in this case is usually 30m
Since it is A or less, there is no possibility that an inspected worker who receives an electric shock will be directly damaged, but if the device is an overhead crane, that is, if the electric motor to be inspected is installed at a high place, an electric shock is generated. The shock may cause a serious accident in which the worker falls.

In order to deal with such a problem and enhance safety, conventionally, an auxiliary device for manually opening and closing the main circuit is provided in front of the static switch, and the above auxiliary is provided when inspecting the electric motor. The device is being opened. However, such an auxiliary device is not necessary when an electromagnetic contactor is used to control the electric motor,
In particular, an operator who has become accustomed to a device using an electromagnetic contactor often forgets to open the auxiliary device before performing the inspection work, which cannot sufficiently enhance safety. ..

Further, in the static switch, since it is necessary to suppress the temperature rise of the thyristors 2 and 3 caused by the load current flowing to the rated junction temperature or less, it is possible to attach radiating fins to the thyristors 2 and 3. Has been done. However,
In the conventional static switch, the thyristors 2, 3 are provided for each phase.
However, since the thyristors 2 and 3 are interposed, the space required for attaching the thyristors 2 and 3 and the heat radiation fins becomes large, which causes a problem that the size of the entire apparatus is increased.

In order to cope with such a problem, the power supply side terminal and the load side terminal for one phase are connected by a short-circuit piece instead of the thyristor.
Also, it is considered to reduce the space required for attaching the heat radiation fin, but with this configuration, a large electric shock current will flow in the event of an electric shock accident as described above, and safety will increase. It was difficult to realize from the viewpoint of sex. If the load current becomes larger,
A cooling fan is also provided in addition to the radiation fins. However, with this configuration, the size of the entire device is further increased, and the service life of the static switch is shortened depending on the service life of the cooling fan. become.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a semiconductor switching element and a surge absorbing circuit connected in parallel between a power source side terminal and a load side terminal, while ensuring safety against electric shock. (EN) Provided is a static switch which has the effects of improving the property and suppressing the temperature rise of the semiconductor switching element and realizing the miniaturization of the entire semiconductor switching element at the same time.

[0010]

In order to achieve the above object, the present invention provides an external operation signal between two pairs of a power supply side terminal and a load side terminal pair for each phase provided in a three-phase energization path. The semiconductor switching element and the surge absorbing circuit that are turned on and off by the above are connected in parallel, and the other pair is connected by a short-circuit piece, and then a relay contact is interposed in each phase energization path, and the semiconductor switching element The control means is provided to turn on the relay contact before turning on the relay contact and to turn off the relay contact after turning off the semiconductor switching element.

[0011]

The relay contact interposed in each phase energization path is turned on before the semiconductor switching element is turned on, and turned off after the semiconductor switching element is turned off. Since it is performed by the element, there is no possibility of shortening the life due to contact wear. When the semiconductor switching element is turned off, the relay contact is also turned off, and the power supply path for each phase is completely cut off.In this state, leakage current may flow to the load side via the surge absorption circuit. Thus, the power supply voltage is not applied to the load side via the short-circuit piece, and the electric shock accident on the load side is reliably prevented.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

In FIG. 1 showing the circuit structure, normally open type relay contacts 11a, 11b, 11c are provided between each pair of power source side terminals R, S, T and load side terminals U, V, W. The circuit unit 12 is connected.

The main circuit section 12 includes an anti-parallel circuit of power thyristors 13 and 14 which are semiconductor switching elements in the first phase (RU phase) corresponding to the relay contact 11a.
Non-linear resistance element 15a, capacitor 15b and resistance 1
The third phase (T-W phase) corresponding to the relay contact 11c is connected in parallel with the surge absorbing circuit 15 composed of 5c.
In the anti-parallel circuit of the power thyristors 16 and 17 which are semiconductor switching elements, and the surge absorbing circuit 15
And a surge absorbing circuit 18 having the same configuration as the above are connected in parallel. In the main circuit section 12, the second phase (SV phase) corresponding to the relay contact 11b is connected by the short-circuit piece 19.

The input circuit section 20, which is a control circuit, has a voltage input section 21 for receiving an external operation signal output through an input terminal A1 to A3 in response to an ON operation of an automatic reset type normally open ON command switch (not shown). The operation control section 22 receives the output of the voltage input section 21.

The operation control section 22 turns on the first light emitting diode 22a according to the rise of the external operation signal when the external operation signal is applied through the voltage input section 21, and turns on the second light emitting diode 22b for a predetermined time. The lights are delayed by .tau.1 and the light emitting diodes 22a and 22b are turned off at the same time when the input of the external operation signal is stopped. In addition, the operation controller 22 controls the first light emitting diode 2
ON command signal Son to line 22c in synchronization with lighting of 2a
Output is started, and when the predetermined time τ2 has passed after the second light emitting diode 22b was turned off, the ON command signal S
Stops output of on.

The indicator 23 lights up with the ON command signal Son being output to the line 22c, and the relay control section 24 is also provided with the ON command signal Son being output to the line 22c. ~ 11c is configured to be turned on.

The auxiliary output circuit section 25 comprises a light receiving section 26 and an auxiliary opening / closing section 27. The light receiving unit 26 has a phototransistor 26a that constitutes a photocoupler with the first light emitting diode 22a, and turns on an auxiliary contact (not shown) in the auxiliary opening / closing unit 27 with the phototransistor 26a turned on. Is configured. still,
In the ON state of the auxiliary contact, the circuit for applying the external operation signal to the terminals A1 to A3 is configured to be self-holding. Such a self-holding state is an automatic reset type normally closed type not shown. It is released in response to the off operation of the off command switch.

The trigger circuit section 28 comprises a light receiving section 29 and a trigger circuit 30. The light receiving section 29 has a phototransistor 29a that forms a photocoupler with the second light emitting diode 22ba, and in the state where the phototransistor 29a is turned on, the gate of each of the thyristors 13, 14, 16, 17 is passed through a trigger circuit 30. Is configured to provide a gate signal to.

Next, the operation of the above configuration will be described with reference to FIG.

Now, at a timing t1 in FIG. 2, when an external operation signal is applied to the terminals A1 to A3 in response to an ON operation of an automatic reset type ON command switch (not shown),
In response to this, in the input circuit section 20, the operation control section 22
However, the first light emitting diode 22a is turned on, the ON command signal Son is output to the line 22c, and the second light emitting diode 22b is turned on at the timing t2 when the predetermined delay time τ1 has elapsed.

Then, at the timing t1, the phototransistor 26a in the auxiliary output circuit section 25 is turned on in response to the lighting of the first light emitting diode 22a, so that the auxiliary contact (not shown) in the auxiliary opening / closing section 27 is turned on. , A circuit for applying an external operation signal to the terminals A1 to A3 in response to the turning on is self-held. Therefore, even after the ON operation of the ON command switch is released after this,
External operation signals are continuously applied to the terminals A1 to A3. Further, at the timing t1, the display 23 is turned on by the ON command signal Son, and the relay controller 24 turns on the relay contacts 11a to 11c.

Further, at the timing t2 which is delayed by time τ1 from this, the phototransistor 29a in the trigger circuit unit 28 is turned on in response to the lighting of the second light emitting diode 22b, so that the light receiving unit 29 causes the trigger circuit. A gate signal is applied to each gate of the thyristors 13, 14, 16 and 17 through 30 and these thyristors 13, 14, 1 and
6 and 17 will be turned on.

Therefore, the power source side terminals R, S, T and the load side terminals U, V, W are brought into a conductive state, respectively, and thus each phase energization path for the load is formed.

When the automatic reset type OFF command switch (not shown) is turned off at the timing t3 in FIG. 2 in such an energized path forming state, the above-mentioned external contact by the auxiliary contact (not shown) in the auxiliary opening / closing part 27 is performed. The self-holding state of the operation signal is released. Then, the input circuit unit 2
At 0, the operation control unit 22 turns off the first light emitting diode 22a and the second light emitting diode 22b, and stops outputting the ON command signal Son to the line 22c when the delay time τ2 elapses after the turning off. Like

Therefore, at the timing t3, since the phototransistor 26a in the auxiliary output circuit section 25 is turned off, the auxiliary contact (not shown) in the auxiliary opening / closing section 27 is turned off to return to the initial state, and the trigger is generated. Since the phototransistor 29a in the circuit unit 28 is turned off, the light receiving unit 2
9 stops the output of the gate signal through the trigger circuit 30 to turn off the thyristors 13, 14, 16 and 17, and accordingly the respective phase energization paths are cut off.

At the timing t4 which is delayed by the time τ2 from this interruption, the operation control section 22 causes the ON command signal Son to occur.
To stop the output, the relay controller 24 causes the relay contact 1
The display 23 is turned off while turning off 1a to 11c.

In summary, the relay contacts 11a to 11c interposed in each phase energization path are the thyristors 13 and 14,
It is turned on for a time τ1 before turning on 16 and 17,
In addition, the thyristors 13, 14, 16 and 17 are turned off when the time .tau.2 has elapsed after the thyristors 13, 14, 16 and 17 were turned off. Therefore,
Opening and closing of the load energizing path is performed by thyristors 13, 14, 16, 1
7 is performed, and there is no risk of shortening the life due to contact wear.

In this case, the thyristors 13, 14, 16,
In the state where 17 is turned off, the relay contacts 11a to 11c
Is also turned off to completely shut off each phase energization path. In this state, leakage current flows to the load terminals U, V, W through the surge absorbing circuits 15 and 18, short circuit pieces The power supply voltage is not applied to the load terminals U, V, W via 19 and the electric shock accident on the load side is reliably prevented.

Moreover, among the three-phase load conducting paths, the power source side terminal S and the load side terminal V for one phase are connected by the short-circuit piece 19, so that the thyristors 13 and 1 are provided.
The area of the radiation fins required to cool 4, 16, 17 and thus their thyristors 13, 14, 16, 17
Also, the installation space for the radiation fins can be reduced, and the overall size of the device can be reduced.

Incidentally, when the switching capacity of the main circuit portion is 50 A, in the prior art, it is necessary to install the main circuit portion of 2A.
While the area of about 42 cm ² is required, the area required for the installation of the main circuit portion 12 configured as in the above embodiment is about 165 cm ² . Further, when the opening / closing capacity of the main circuit portion was 50 A, in the prior art it was necessary to provide a cooling fan in addition to the radiation fins. However, according to the configuration of this embodiment described above, the radiation fins are installed. A cooling fan can be dispensed with simply by expanding the area to about 546 cm ² , and it is possible to prevent the size of the entire apparatus and the shortening of the life due to the provision of the cooling fan.

In the above embodiment, the internal signal transmission is performed by an optical signal, but such a configuration may be adopted if necessary.

[0033]

According to the present invention, as is clear from the above description, the semiconductor switching element and the surge absorbing circuit are connected in parallel between the power source side terminal and the load side terminal, but the opening and closing of the load conducting path is performed. Is performed by turning on and off the semiconductor switching element, and when the semiconductor switching element is turned off, the load energization path is cut off by the relay contact, so that the safety against electric shock can be improved without impairing the original advantage of extending the life. In addition, since one of the three phases is connected by the short-circuit piece instead of the semiconductor switching element, it is possible to suppress the temperature rise of the semiconductor switching element and to reduce the overall size at the same time. ..

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention.

FIG. 2 is a timing chart for explaining the operation

FIG. 3 is a partial circuit configuration diagram for explaining a conventional example.

[Explanation of symbols]

In the figure, R, S and T are power supply side terminals, U, V and W are load side terminals, 11a, 11b and 11c are relay contacts, 12 is a main circuit section, 13, 14, 16 and 17 are thyristors (semiconductor switching). Elements), 15 and 18 are surge absorbing circuits, 19
Is a short-circuit piece, 20 is an input circuit unit (control circuit), 22 is an operation control unit, 24 is a relay control unit, and 28 is a trigger circuit unit.

Claims (1)

[Claims] 1. A semiconductor switching element and a surge absorbing circuit that are turned on / off by an external operation signal are connected in parallel between two pairs of power-side terminals and load-side terminal pairs for each phase provided in a three-phase energization path. And a static switch formed by connecting another pair by a short-circuit piece, wherein the relay contacts are respectively interposed in the current-carrying paths for each phase, and the relay contact is provided prior to turning on the semiconductor switching element. And a control means for controlling the relay contact so that the relay contact is turned off after the semiconductor switching element is turned off.