JPS5937613B2 - Semiconductor circuit breaker - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor breaker, and more particularly to a semiconductor breaker using a power transistor as a switching element.

There is a thyristor breaker using a thyristor as a conventional semiconductor breaker.

Since the SIRISC circuit breaker was designed to turn off by passing a reverse current through the SIRISK in the event of a failure, it required a commutation circuit to supply reverse current.

The thyristor breaker will be briefly explained below with reference to FIG.

In Figure 1, 1' is a power supply, 2' is a current transformer, 3' is a main thyristor unit, 4' is a load, 5' and 6' are auxiliary diodes, 7' is an auxiliary thyristor, 8', 9' and 10'
is a charging/discharging circuit, 11' is a detection circuit, 12' is a control circuit,
13' is a rectifier, 14' is a transformer, and 15' is an AC power source.

As shown in FIG. 1, the AC power supply 15' is normally connected to the rectifier 13
' converts it to direct current and charges the capacitor 10'-1, and in the event of a short-circuit failure, the current transformer 2' detects it and fires the auxiliary thyristor 7' through the detection circuit 11' and the control circuit 12'. , a reverse current was flowing through the main thyristor unit 3' through the auxiliary diodes 5' and 6'.

For this reason, a charging/discharging circuit 8' including a capacitor 10'-1,
9', 10', auxiliary diode 5/.

A commutation circuit including circuit breaker 6', etc. is required, and each component forming this commutation circuit accounts for about 30% of the total cost of the breaker.

In addition, it occupies 35% of the space, and the charging voltage of capacitor io'-i is usually higher than the main circuit voltage, so even if the main circuit voltage is low, capacitor 10'
-1 voltage is high voltage and has the disadvantage of being treated as high voltage.

These drawbacks arise from the fact that, due to the use of thyristors, it is necessary to flow a reverse current when current limiting is cut off.

The present invention has been made in view of the above points, and uses a power transistor as the main circuit current element to eliminate the need for a conventional thyristor type commutation circuit for flowing reverse current, resulting in significant cost reduction and space saving. In order to improve safety by reducing the size of the circuit breaker and making it possible to use only low-voltage circuits, when a fault current occurs, three phases are cut off at the same time to prevent phase loss from being supplied to the load. To provide a semiconductor breaker capable of supplying maximum allowable current to a load even if the waveform of the load current changes or the ambient temperature changes in an inverter power source.

An embodiment of the present invention will be described below with reference to FIG.

In Figure 2, 1 is a 3-phase AC power supply, 1-1゜1-2, 1-
3 is a power supply for each phase of R phase, S phase, and T phase.

2 indicates a three-phase load, 2-1.2-2゜2-3 is the R phase,
The load of each phase of S phase and T phase is shown.

3 is a current transformer, and 3-1 and 3-2 are current transformers for each phase, R phase and T phase.

4 is the auxiliary transformer 4-L4-2.4-3.4-4.4-
5 is each winding from the first order to the fifth order.

5 is an R-phase semiconductor breaker unit, a single-phase full-wave rectifier consisting of diodes 5-1 to 5-4, 5-5 a resistor,
5-6 is a capacitor, 5-7 is a resistor, 5-8 is a photocoupler light receiving element, 5-9 is a resistor, 5-10 is a speed-up capacitor, 5-11 and 5-12 are power transistors, -13 is a diode, 5-14 is a non-linear surge absorption element, 5-15 is a diode, 5-16 is a resistor, 5-17 is a capacitor, and 5-18 is a temperature-sensitive resistance element. ing.

Reference numerals 6 and 7 denote S-phase and T-phase semiconductor breaker units, which are the same as the R-phase semiconductor breaker unit 5, so the details will be omitted.

8 is a semiconductor breaker control circuit, 8-1 to 8-4 are diodes that constitute a single-phase full-wave rectifier, 8-5 is a resistor,
8-6 is a capacitor, 8-7 is a person, contact point for disconnection signal, 8-
8 is a large display light emitting diode, 8-9 is an NPN) transistor, 8-10 is a constant voltage diode, 8-11 is a diode, 8-12 is a diode, 8-13 is a constant voltage diode, 8-14 is a resistor , 8-15 to 8-17 are photocoupler light emitting elements, 8-18 is a resistor, 8-19 is a capacitor, 8-20 is a constant voltage diode, 8-21 is a resistor, 8-22 is a light emitting diode, 8-23 is a gate turn-off thyristor (hereinafter referred to as GTO), 8-24 is a diode, 8-25 is a diode, 8-26 is a constant voltage diode, 8-27 is a variable resistor, 8-28 is a resistor,
8-29 is an overload relay, 8-30 to 8-35 are diodes that constitute a three-phase full-wave rectifier, 8-36 is a resistor, 8-37 is a diode, 8-38 is a variable resistor, 8-36 is a resistor, 8-37 is a diode, 8-38 is a variable resistor, −
Reference numeral 39 denotes a constant voltage diode, which is composed of each of these elements.

9 is a control power source for the semiconductor breaker.

Next, the operation of the semiconductor breaker having the above configuration will be explained.

Control power for the semiconductor breaker is supplied from a control power source 9.

It is transformed by converting it into an auxiliary transformer, is supplied to the semiconductor breaker control circuit from the fifth winding 4-5, and is connected to the diode 8-1.
It is converted into a DC voltage by a single-phase full-wave rectifier constituted by 8-4.

A filter circuit is configured by a resistor 8-5 and a capacitor 8-6 to smooth the DC voltage.

When the signalable contact 8-7 is closed, the resistor 8-18 is connected between the parallel circuit of the constant voltage diode 8-20 and the capacitor 8-19, the resistor 8-2l, the NPNI, and the base and emitter of the transistor 8-9. - The base current of the NPNI transistor 8-9 flows through the path of the resistor 8-14 and the light emitting elements 8-15 to 8-17 of the photocoupler.

As a result, a collector current flows and the large display light emitting diode 8-8 lights up.

Sufficient current flows through the light emitting elements 8-15 to 8-17 of the photocoupler and the light receiving element 5- in the semiconductor breaker unit 5.
8 phototransistors each switch on at high speed.

As described later, this causes the power transistor 5-
12 is switched on and power is supplied to the load 2.

Similarly, the S-phase and T-phase semiconductor breaker units 5 and 7 are also switched on, and power is supplied to the load 2.

Next, when a short circuit fault occurs, the fault current is detected by current transformer 3-1 or 3-2, and this secondary current is further processed by a three-phase full-wave rectifier consisting of diodes 8-30 to 8-35. rectified, resistor 8-28 and variable resistor 8-
27 into a voltage signal.

When the voltage across the variable resistor 8-270C-L exceeds the Zener voltage value of the constant voltage diode 8-26, a signal is supplied to the gate of the GTO 8-23 via the diode 8-25, and the GTO 8-23 Turn on.

As a result, the charge on the capacitor 8-19 is transferred to the light emitting diode 8-22-GTo 8--23 A- for trip display.
Between - constant voltage diode 8-13 - diode 8-1
2-flow through the path of resistor 8-21, and photocoupler light emitting elements 8-17 to 8-15-resistor 8-14-NPN
) It flows between the emitter and base of the transistor 8-9 and through a parallel circuit of the constant voltage diode 8-10 and the diode 8-11.

This supplies a reverse current between the emitter and base of the NPN transistor 8-9, causing it to switch on at high speed.

Since the overcurrent withstand capacity and allowable heat loss of the power transistor 5-12 are small, if the base signal is not turned off quickly in the event of a failure, the power transistor 5-12 will be destroyed, so a technique for switching off the base signal quickly is required.

By supplying a reverse current to the aforementioned NPN) transistor 8-9, the photocoupler light emitting elements 8-15 to 8-17
The light emission stops at a high speed.

The supply of reverse current turns off the NPN transistors 8-9 at an extremely high speed.

This is because the accumulated carriers are removed at high speed by the reverse current.

As a result, the photocoupler light emitting elements 5-8, (61,
7-8) is switched on at high speed, power transistors 5-12 and (6-12, 7-12) are simultaneously switched on at approximately μSeC order, and the fault current is removed at high speed.

Since the GTO 8-23 remains on, the trip display light emitting diode 8-22 remains on.

GTO8-23 reset operation is on/off signal contact 8-
By turning off GTO8-23, the current of GTO8-23 is made lower than the holding current and turned off.

Next, the tripping operation at the time of overload will be explained.

During overload, a voltage signal is generated by overload relay 8-29, which supplies a gate signal to the gate of GTO 8-23 via diode 8-24.

The subsequent operation is the same as the tripping operation when a short-circuit fault occurs, so it will be omitted.

Next, the operation of each phase semiconductor breaker unit 5, 6, and 7 according to the commands of the semiconductor breaker control circuit 80 will be explained.

Insulation of the semiconductor breaker unit 5.6.7 of each phase and supply of control power are performed by the second to fourth artificial windings 4-2 to 4-4 of the auxiliary transformer.

The operation of the R-phase semiconductor breaker unit 5 will be explained.

The AC voltage of the secondary winding 4-2 of the auxiliary transformer 4 is rectified by a single-phase full-wave rectifier consisting of diodes 5-1 to 5-4, and is composed of a resistor 5-5 and a capacitor 5-6. The bases of power transistors 5-11 and 5-12 are smoothed by a filter and connected to the bases of power transistors 5-11 and 5-12 through a resistor 5-7, a photocoupler light receiving element 5-8, a resistor 5-9, and a speed-up capacitor 5-10. Supply base current between emitters.

When the light receiving element 5-8 of the photocoupler is switched on, the speed is increased by the capacitor 5-10, and the Darlington-connected power transistors 5-11 and 5-12 are switched on at high speed.

A half-wave of AC power is supplied to the load 2 through a diode 5-13, and a reverse half-wave is supplied to the load 2 through a power transistor 5-12.

Surge energy when the power transistor 5-12 is switched on is absorbed by the capacitor 5-17 through the diode 5-15.The resistor 5-16 is a resistor for discharging the capacitor 5-17.

Surge energy is also absorbed by the non-linear surge absorbing element 5-14.

The contact 8-7 of the OFF signal is opened, the NPNI transistor 8-9 is switched off, and the light emitting element 8 of the photocoupler is turned off.
-15 stops emitting light, the photocoupler's light receiving element 5-
8 is turned off and the base current is cut off.

The photocoupler response ranges from 100Nsec to several μs.
Many are in the ec range.

The response of the photocoupler used in the present invention is also sufficient within this range, and the time required from the occurrence of a short-circuit accident to the removal of the fault current is within several tens of microseconds, and high-speed cutoff is possible. 12 is not destroyed.

For overcurrent protection, when an overload failure occurs, the overload is detected by the overload relay 8-29, and the power transistors 5-12. (6i2,7-12) is turned off.

When driving a high-frequency motor with an MG, the overload relay may be designed to detect the magnitude and frequency of the sinusoidal current in the flowing load current from startup to steady operation. In addition to the magnitude and frequency of the load current, the waveform also changes, so it is difficult to detect the magnitude of the load current with equal constraints based on the current peak value.

The output voltage waveform changes depending on the inverter's commutation method, and the load current waveform also differs.

On the other hand, if a filter is installed in the overload relay and the charging/discharging time is kept constant (0.1 seconds to 1 second), a practical actual value current can be detected, but in the event of an overload failure, the peak current will also increase and the power will increase. The voltage between the emitter and collector of transistor 5-12 increases, which may cause overheating.

In the present invention, the time constant for charging and discharging the filter is set at around 0.7 seconds, and even before the operation time of the overload relay 8-29, the power transistors 5-12, (6-12
, 7-12) is detected by the temperature-sensitive resistance element 5-18 which is integrally attached to the power transistor, and when the temperature of the power transistor rises to the upper limit of the allowable rise value, the temperature-sensitive resistance element 5-18 is detected. 18 is detected as a resistance change, the base signal of the power transistor 5-12 is cut off, and the main circuit current is turned off.

As a method other than the present invention, until the influence of the waveform disappears,
There is a method of increasing the rated current of the breaker, but in this case, it is necessary to increase the rated current to about 1.5 times that of the present invention, which has the drawback of being extremely uneconomical.

Increasing the rated current by 1.5 times usually requires a large one-rank fin, power transistor, or a power transistor with a large rating, so the space is also large (which has the disadvantage of being large).

The present invention eliminates these drawbacks by the means described above.

Next, this operation will be explained.

integrally attached to the power transistor 5-12,
A constant DC voltage is applied to the temperature-sensitive resistance element 5-18 through a filter circuit of a resistor 8-36 and a constant voltage diode 8-39, and this constant voltage causes a constant bias current to flow through the temperature-sensitive resistance element 5-18. Increase the temperature response speed of the temperature sensitive resistance element.

As a result, when the temperature of the power transistor 5-12 reaches a set temperature value that does not exceed the allowable rise value, the resistance is changed in about several microseconds to respond.

What was always a divisor of 10 Ω has been changed to an operating special divisor of 100 Ω.
can be suddenly changed.

When the temperature sensitive resistance element operates, the voltage between the variable resistor 8-380C-L increases and the voltage across the GTO 8-2 increases through the diode 8-37.
Send gate signal to 3.

The subsequent operation is similar to the operation at the time of short-circuit failure or overload described above, and the power transistor 5-12 is turned off at a high speed.

Since a temperature-sensitive resistance element is used, even if the ambient temperature changes throughout the seasons and the allowable current of the power transistor 5-12 varies throughout the seasons (allowable current rate at high ambient temperature), the power is maintained by the temperature-sensitive resistance element 5-18. Since the temperature rise of the transistor 5-12 is detected and turned off before it is destroyed, the set value of the overload relay 8-29 can be increased to the maximum allowable value if requested by the load side.

Therefore, it is used very efficiently and is economical.

Even if the semiconductor breaker of the present invention is used at the lower level and the silice breaker is used at the upper level, even in the event of a short-circuit accident, the lower level breaker will maintain the value of the base current of the power transistor multiplied by the DC current amplification factor (hFE). Only collector current flows,
The current value does not reach the set operating value of the upper thyristor breaker, and the lower breaker is reliably tripped first, ensuring selective breaker.

On the other hand, if a thyristor breaker is used on both the upper and lower sides, until the lower circuit breaker trips when a short circuit occurs,
The same fault current flows in both the upper and lower parts, and its maximum value is much larger than the maximum value when the breaker of the present invention is used in the lower part.The detection circuit of the upper thyristor breaker also operates, and the thyristor breaker of the lower part and the upper part Problems sometimes occurred in which the circuit breakers tripped at the same time.

This drawback can be completely eliminated by using the semiconductor breaker of the present invention.

The present invention, which uses a power transistor in the main circuit and uses a current transformer to detect current, has extremely superior features compared to a thyristor type semiconductor breaker.

In a thyristor-type semiconductor breaker, the fault current in the main circuit increases in proportion to the magnitude of the back power, from when the fault current is detected to when the fault current is limited by supplying a reverse current. However, the disadvantage was that the current would flow through it.

However, when a power transistor is used in the main circuit, the value obtained by multiplying the base current by the DC amplification factor (hFE) only flows as the collector current, and it is not related to the bank power (the flowing current is constant and the current transformer Since only a constant current flows through each when short-circuited, resistor 8-28 and variable resistor 8-2
It also has the advantage that the voltage across the terminal 7 is extremely small compared to when a thyristor breaker is used.

This feature eliminates the need for a semiconductor breaker control circuit and an overvoltage control circuit (a combination of a voltage regulator diode and a resistor, or the use of a varistor), making it possible to use an extremely reliable and compact semiconductor breaker control circuit. There are certain advantages.

Conventional thyristor circuit breaker could not have this feature.

Unlike thyristor circuit breakers, there is no need to provide a reverse current supply circuit, resulting in smaller size and higher reliability.
High-speed reloading is possible.

As described above, since the semiconductor breaker according to the present invention does not require a commutation circuit for flowing reverse current, it is possible to significantly reduce costs and space.

In addition, since there is no need for a high-voltage circuit to charge the capacitor for flowing reverse current to the main thyristor, the entire circuit of the circuit breaker is a low-voltage circuit, which improves safety. It can be used because a transistor is used as the main circuit current switching element, and even if the waveform of the load current is different or the ambient temperature changes, the temperature of the power I transistor itself is detected, so it can be used for general purpose. It has the advantage of being able to be used for many purposes, has a large breaking current, allows for high-speed re-opening, and can be opened and closed frequently.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing a conventional thyristor breaker;
The figure is a circuit diagram showing a semiconductor breaker according to an embodiment of the present invention. 1... 3-phase AC power supply, λ... 3-phase load, DI... current transformer, 4... auxiliary transformer,
5, 6, 7... Semiconductor breaker unit, 5-
18...Temperature sensitive resistance element, 8...Control circuit, 8-9...NPNI-transistor, 8-1
5-8-17...Photocoupler light emitting element, G
TO......Gate turn-off thyristor, 8-2
9... Overload relay, 9... Control power supply.

Claims (1)

[Claims] 1. In a semiconductor circuit breaker using a transistor as a switching element between a power source and a load, a first circuit breaker detects a short circuit fault and an overload fault and cuts off the base current of the transistor when the current value reaches a set value. A protector is provided, and a temperature-sensitive resistance element is provided integrally with the transistor and detects a temperature change of the transistor as a resistance change, and when the detected temperature of the transistor reaches a set temperature value that does not exceed the allowable rise value, the above-mentioned a second protector that cuts off the base current of the transistor;
A semiconductor breaker operates in parallel with a protector, and when the protector operates sooner, the base WLR of the transistor is cut off, the transistor is turned off, and the fault current is cut off.