JPS6123754B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power control device with improved power cutoff characteristics.

Controlled rectifier elements (hereinafter referred to as thyristors) are often used in power control devices that directly convert AC power into electric power or control the amount of AC power.

A power control device adjusts the voltage or amount of current applied to a load depending on the purpose, but depending on the application, it may be required to cut off power instantaneously.

When an overload or short circuit occurs in a variable frequency variable voltage inverter that controls a motor, or a DC power supply for electrolytic processing machines or plating, the current should be turned off to minimize damage to the load side or the power supply itself. It is desirable to shut it off instantly.

An example of a conventional power control device will be explained with reference to FIG. FIG. 1 shows a general single-phase mixed bridge rectifier circuit. 1 is an AC terminal, 2 is a load, and 3 is a power control circuit including a thyristor. There is no need to explain the operation shown in Fig. 1, but as shown in Fig. 2 a, the amount of power supplied to the load 2 with single-phase full-wave current output can be controlled by the firing phase angle of the thyristor. . Now, when it is turned off at an arbitrary time as shown in Figure 2 b, if the relationships shown in Figure 2 a and b are established in terms of time, the load current becomes zero because the phase of the power supply is There is a delay of t ₀ until it reaches zero. In this case, there will be a maximum delay of 1/2 cycle of the power supply frequency.In addition, as shown in Figure 3, if the DC side load is inserted into the AC side and the DC terminals are short-circuited, it is possible to control the AC power. The operation delay is exactly the same as in FIG. As shown in Figures 1 and 3, connecting the AC power supply and the load for 1/2 cycle of the power supply frequency in an emergency could lead to a fatal accident, so the shortest possible time ( For example 50~
We need something that can cut it off in 100 microseconds).
Conventionally, either the circuit characteristics shown in Figures 1 and 3 were satisfied, or the load 2 was placed on the DC side as shown in Figure 4.
A method of inserting a chopper 4 in series with this is used. In the latter case, a thyristor dedicated to the chopper is required in the main circuit, making the device large and expensive.

This invention aims at simplifying the circuit by providing a thyristor group that performs power adjustment through firing angle control with a chopper function so as to be able to instantaneously cut off the load in addition to the power control function. This invention will be explained below with reference to the drawings.

FIG. 5 shows an embodiment of the present invention, in which 1 is an AC terminal, 2 is a load, and 3 is a power control circuit including a thyristor and a diode, the anodes of the thyristors are connected to different phases of the AC terminal 1, and the cathodes and are commonly connected. 8 is a diode rectifier whose anodes are each connected to the AC terminal 1 and whose cathodes are commonly connected; 5 is a rectifier element 8
6 is an arc-extinguishing capacitor connected between the cathode of the arc-extinguishing thyristor and the common connection terminal of the thyristors of the power control circuit 3; 6 is charged by an auxiliary power source 15. That is, since the auxiliary power supply 15 is connected to the capacitor 6 via the rectifier 13 and the current limiting resistor 14, the capacitor 6 is connected to the above-mentioned It is slowly charged by a sufficiently small current that is less than the holding current of the arc thyristor 5. 7 is an inverting thyristor that reverses the voltage polarity of the arc extinguishing capacitor 6; 9 and 10 are rectifiers and capacitors that prevent the arc extinguishing capacitor 6 from being overcharged; 11 is a reactor that suppresses the rise of current; 12 is a This is a DC reactor connected in series with load 2.

The details of the operation will be explained below using the embodiment shown in FIG.

Normally, a current I _L is supplied from an AC terminal 1 to a load 2 via a power control circuit 3 including a thyristor and a DC reactor 12 .

On the other hand, if an abnormality occurs on the load side and the current is instantaneously cut off, the gate signal of the thyristor in the power control circuit 3 is stopped, and at the same time the gate signal of the thyristor in the power control circuit 3 is stopped.
A gate signal is sent to the arc-extinguishing capacitor 6 to form a discharge path.

When the arc-extinguishing thyristor 5 first becomes conductive, the charge in the arc-extinguishing capacitor 6 flows to the thyristor that is sharing the load current I _L of the power control circuit 3 in the direction of canceling the load current, and further flows to the AC terminal. The discharge occurs through the rectifying element 8 connected to the arc-extinguishing thyristor 5, the arc-extinguishing thyristor 5, and the reactor 11. When this discharge current I ₂ becomes larger than the load current I _L , the discharge current of the arc-extinguishing capacitor 6 is reduced to the DC reactor 1.
2. The load 2, the diode in the lower arm of the power control circuit 3, the rectifying element 8 connected to the AC side terminal of the diode and the arc-extinguishing thyristor 5, the arc-extinguishing thyristor 5, the flow to the reactor 11, and the arc-extinguishing capacitor. The polarity of the voltage 6 is reversed and the oscillating discharge current becomes zero. Then, a reverse voltage is applied to the thyristor of the power control circuit 3 until the voltage of the arc-extinguishing capacitor 6 crosses the zero potential, so that the arc is completely extinguished. Due to the above-described arc-extinguishing action, the load current can be interrupted within a short time determined by the arc-extinguishing circuit constant, regardless of the phase of the power supply voltage.

In order to return the voltage polarity of the arc extinguishing capacitor 6 to its initial state, the inverting thyristor 7 is made conductive and a current I ₁ is caused to flow through the DC reactor 12. Therefore, the voltage polarity of the arc-extinguishing capacitor 6 can be returned to its initial state within a short time.

Thereafter, the load current of the power control device using phase control can be instantaneously interrupted by the same operation.

The reactor 11 shown in FIG. 5 is used to control the current rise (di/
dt) was inserted for the purpose of suppressing it, and is unnecessary in terms of the operation explanation.

Moreover, the series circuit of the rectifier 9 and the capacitor 10 inserted between the connection point of the rectifying element group 8 and the arc-extinguishing thyristor 5 and the DC bus bar absorbs inductive energy when the load current of the load circuit and AC power supply circuit is cut off. This prevents the arc-extinguishing capacitor 6 from being overcharged. The energy stored in the capacitor 10 is slowly discharged by a discharge circuit (not shown).

6a and 6b show the operating characteristics of the circuit shown in FIG. 5, and correspond to FIGS. 2a and 2b. As a result, it is understood that the load current is instantaneously cut off in response to an ON-OFF command from the current control device.

FIGS. 7 to 10 show circuits showing other application examples of the present invention. 7 and 8 show an example of three-phase full-wave connection, and FIG. 9 shows an example of three-phase center-tap connection. FIG. 10 shows a case where the load 2 is connected to an AC example in a three-phase full-wave connection circuit. The operating principle is the same as the example shown in FIG. Note that in the circuits shown in FIGS. 7 to 10, an auxiliary power source 15 for charging the arc-extinguishing capacitor 6 as shown in FIG.
The charging circuit including this is not shown.

In all of the embodiments shown in FIGS. 5, 7 to 10, in order to return the voltage polarity of the arc-extinguishing capacitor 6 to its initial state, the inverting thyristor 7 is made conductive.
This is done by passing a current _I1 through a DC reactor 12.

That is, as shown in FIG. 12, after the voltage V _C of the arc extinguishing capacitor 6 is discharged by the conduction ON of the arc extinguishing thyristor 5, the polarity of the voltage V _C is reversed and the oscillating discharge current becomes zero. When the inverting thyristor 7 is turned on, the polarity of the voltage V _C of the arc-extinguishing capacitor 6 can be returned to the initial state in a short time, so the next operation is performed after the arc-extinguishing thyristor 5 conducts once. Time until it becomes possible (deactivation time)
can be shortened. In Figure 12, period
The lengths of T ₁ and T ₂ are determined by the circuits and elements used, but in the case where the inverting thyristor 7 is provided, the lengths of T 1 and T 2 can usually be several tens of microseconds.

Incidentally, FIG. 11 shows an example in which the inversion thyristor 7 is not provided. FIG. 11 is an example of a three-phase full-wave connection circuit in which an independent auxiliary power supply 15 is used in the inverting circuit of the arc-extinguishing capacitor 6. In devices where the frequency of interruption is low, the arc extinguishing capacitor 6 is slowly charged through the path of the rectifier 13, current limiting resistor 14, and auxiliary power source 15, and finally the voltage V
This is what is kept in _C.

The advantage of the circuit shown in FIG. 11 is that since the voltage of the arc-extinguishing capacitor 6 is always maintained at V _C , the arc-extinguishing ability is guaranteed and the reliability against interruption is improved.

However, in the case where the inverting thyristor 7 is not provided in series with the arc-extinguishing capacitor 6 as in the circuit shown in FIG. 1
4. In order to charge slowly in the path of the auxiliary power supply 15 with a small current that is less than the holding current of the arc-extinguishing thyristor 5, the length of the period _T3 is the first as shown in FIG.
It becomes much longer than the length of T ₂ in Figure 2. (Usually, the length is on the order of seconds.) Therefore, there is a problem that the non-operating time becomes extremely long.

In addition, a current limiting resistor 14 is connected to the arc extinguishing capacitor 6.
There is also the disadvantage that the same amount of energy stored in the capacitor 6 is lost as heat from the resistor 14.

Therefore, the embodiments shown in FIGS. 5, 7 to 10 in which the thyristor 7 as an inverting control rectifying element is connected in series with the arc-extinguishing capacitor 6 have the following advantages.

(a) By operating the arc-extinguishing thyristor 5 once and then operating the reversing thyristor 7, the current
By flowing I ₁ into the arc-extinguishing capacitor 6, the polarity of the arc-extinguishing capacitor 6 can be returned to its original state in a short time.

(b) The current _I1 does not flow to the load 2, but can be returned to the original state via the DC reactor 12 and the arc-extinguishing capacitor 6.

In the above embodiment, an arc extinguishing circuit (generally referred to as a cathode pulse type chopper circuit) in which an arc extinguishing thyristor 5 and an arc extinguishing capacitor 6 are connected in series was explained. Of course, similar effects can be obtained by using an arc extinguishing circuit (generally referred to as a repulsion pulse type chopper circuit) in which the capacitors 6 are arranged in parallel.

As explained above, the present invention forcibly interrupts the current to a plurality of power control thyristors using one set of arc-extinguishing circuits, and there is no need for a thyristor dedicated to interrupting, so the device can be made smaller. This contributes to increasing the number of products and reducing prices. It is easy to understand that this effect becomes more pronounced as the number of alternating current phases increases.

In addition, by using an inversion control rectifier that reverses the polarity of the arc-extinguishing capacitor, it is possible to shorten the time (non-operating time) from when the arc-extinguishing control rectifier becomes conductive until the next time it operates (conducts). Moreover, the current required to reverse the polarity of the arc-extinguishing capacitor
I ₁ does not flow to the load, but instead flows to the arc-extinguishing capacitor via the DC reactor and then returns to the original inverting control rectifier element, making it possible to reliably cut off power to the load.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing a conventional power control device, Fig. 2 is an explanatory diagram of the operation of Fig. 1, Figs. 3 and 4 are circuit diagrams showing other conventional power control devices, and Fig. 5 is a circuit diagram showing a conventional power control device. A circuit diagram showing one embodiment of this invention, FIG.
Figures 7, 8, and 9 show the operating characteristics of Figures 7, 8, and 9.
10 are circuit diagrams showing other embodiments of the present invention, FIG. 11 is a circuit diagram showing an example in which no inverting thyristor is provided, and FIG. 12 is a circuit diagram showing the voltage of the arc extinguishing capacitor in the present invention. Change explanation diagram, 1st
FIG. 3 is an explanatory diagram of the voltage change of the arc-extinguishing capacitor in the same case as shown in FIG. 11. Note that the same reference numerals in the figures indicate the same or corresponding parts. In the figure, 1...AC terminal, 2...Load, 3...Power control circuit, 5...Control rectifier for arc extinguishing, 6...Capacitor for arc extinguishing, 7...Control rectifier for inversion, 8
... rectifying element, 12... reactor.

Claims (1)

[Claims] 1 has at least two or more control rectifying element groups for controlling the amount of power supplied to the load 2, each having a terminal of the same polarity in common, and one polarity terminal being connected to an AC terminal 1 of a different phase, respectively. The power control device has eight groups of rectifying elements whose one end is connected to the AC terminal 1 and whose other ends are commonly connected in the same polarity direction, and the common connection point of the rectifying element group and the control At least an arc-extinguishing control rectifying element 5 and an arc-extinguishing capacitor 6 are connected between the common connection points of the rectifying element group.
is connected in a direction to apply a reverse bias voltage to the control rectifying element group, and a DC reactor 12 is connected in series with the load 2, and between the DC reactor and the load 2, the arc extinguishing An arc-extinguishing capacitor 6 connected in series with the capacitor 6 and changing depending on conduction of the arc-extinguishing control rectifying element 5.
A power control device characterized in that an inversion control rectifier element 7 is connected to restore the polarity of the power control device.