JPS6255730B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a DC/disconnection device having a semiconductor rectifying element and its commutation circuit, and in particular to a DC circuit in which the stored energy of inductance present in the DC circuit is consumed by a non-linear resistor. Regarding DC current and disconnection devices.

As shown in FIG. 1, a DC/disconnection device 1 for protecting DC feeder lines at, for example, electric railway substations, includes a main thyristor 11 and a capacitor 12 that creates a current zero point for these.
A, a commutation circuit 12 consisting of a series circuit of a reactor 12b, and an auxiliary thyristor 12c, and a main thyristor 1
1, a diode 13 connected in antiparallel to the DC circuit, and a non-linear resistor 14 that consumes the energy stored in the inductance of the DC circuit and quickly limits or cuts off the DC current.

Zinc oxide ceramics are used as the non-linear resistor 14 used in such a DC/disconnection device 1, and the electrical equivalent circuit of this is shown in FIG. and capacitance 14b
is represented by a parallel circuit.

However, in general, the absorption energy imposed on the direct current or disconnection device 1 at the time of shear disconnection is extremely large, and for this purpose, a large number of large capacity (large diameter) zinc oxide ceramics are connected in parallel to form a nonlinear resistor 14.
must form a whole. Therefore, the equivalent capacitance 14b of the nonlinear resistor 14 becomes considerably large (for example, about 0.2 μF).

As described above, if a capacitance exists directly in parallel with the main thyristor 11, a problem arises in terms of the turn-on di/dt (current rise rate) withstand capability of the main thyristor 11. Therefore, as shown in Fig. 3, the reactor 15
A method of reducing the rate of increase in the current flowing in from the equivalent capacitance 14b of the non-linear resistor 14 can also be considered, but the following problems occur. In the operation explanatory diagram of FIG. 4, the current 21 of the diode 13 is turned off at t ₂ following t ₁ after the current 20 of the main thyristor 11 is turned off.
Furthermore, due to the carrier accumulation effect of the diode 13, a whisker-like voltage of _V22 is generated in the forward recovery voltage 22 when the main thyristor 11 is turned on. As shown in Fig. 4, this forward recovery voltage V ₂₂ is determined by the inversion voltage of the capacitor V _C and the reactor 1 of the commutation circuit.
If L is the equivalent inductance of 2b, etc., and di/dt is the current change rate of the switching circuit due to the current increase rate of the recovery current of the diode, then it is expressed as V ₂₂ = V _C + Ldi/dt, and it depends on Ldi/dt. A large whisker-like voltage is generated. This forward recovery voltage V ₂₂ is the main thyristor 1
If a non-linear resistor 14 is connected directly in parallel with the non-linear resistor 1, this limit voltage will not be exceeded.However, in the circuit of _FIG . The ability to limit at 14 is diminished. In other words, it becomes necessary to lower the limiting voltage of the non-linear resistor 14, which reduces DC current limiting and breaking ability, and increases stress on the non-linear resistor.

The object of the present invention has been made in view of the above circumstances, and it is an object of the present invention to
The object of the present invention is to provide a direct current and disconnection device capable of suppressing the turn-on di/dt of the main thyristor 11.

An embodiment of the present invention will be described below with reference to a schematic diagram of a direct current disconnection device shown in FIG.

In the figure, 31a is the main thyristor 11 and diode 1.
3 and the commutation circuit 12, and the conductor 31a is passed through a through-type core 32a formed by winding a ferrite core or a silicon steel plate, for example, to constitute a saturable reactor.

With this configuration, the main thyristor 11
Di/
dt is suppressed and the saturable reactor consisting of the through-type core 32a and the conductor 31a is selected so as to be saturated in the circuit current region, the diode 1
The forward recovery voltage V ₂₂ of the main thyristor 11 due to the carry accumulation effect of No. 3 can be set below the limit voltage of the non-linear resistor.

FIG. 6 shows another embodiment of the present invention, in which a common connection conductor 31 of the main thyristor 11 and the diode 13 is connected.
b is passed through the through-type core 32b to constitute a saturable reactor. In this configuration, if the core is selected so that the saturable reactor is saturated in most of the current range where the reverse recovery phenomenon occurs in the diode 13, the commutating circuit current is stable.
In the embodiment shown in the figure, even when the circuit current is small (for example, not during a large current interruption during an accident, but during a small current interruption during a light load), the forward recovery voltage V ₂₂ by the diode 13 can be adjusted appropriately. It is also possible to appropriately suppress di/dt when the main thyristor 11 is turned on.

FIG. 7 shows still another embodiment of the present invention,
Connection conductor 31c of main thyristor 11 and diode 1
A common through-type core 32c with the connection conductor 31d of No. 3
On the other hand, as shown in the figure, the forward current path of the main thyristor 11 and the forward current path of the diode 13 are both penetrated from the same plane. In this configuration, the saturation characteristic as a saturable reactor may be set such that it is saturated in most of the reverse recovery current region of the diode 13, as in the embodiment shown in FIG. The feature of this method is that, from the hysteresis characteristics of the core, the magnetic field caused by the reverse recovery current of the diode 13 has a polarity opposite to the magnetic field generated by the forward current of the main thyristor 11 (the core is reset). It has the advantage of being able to obtain a large voltage/time product.

As described above, by using a saturable reactor as in the present invention in a semiconductor DC circuit or a circuit breaker using a non-linear resistor, the main thyristor 11 due to the inflow from the capacitance of the non-DC resistor. current increase rate of
di/dt can be suppressed, and by selecting appropriate saturation characteristics, transient overvoltage caused by semiconductor carrier accumulation effect can be suppressed to below an appropriate value, which is advantageous in that DC current can be more quickly limited. There are many points.

[Brief explanation of the drawing]

Fig. 1 is a principle block diagram of a direct current and disconnection device using a non-linear resistor, Fig. 2 is an electrical equivalent circuit of a non-linear resistor, Fig. 3 is a block diagram of a conventional device, and Fig. 4 FIG. 5 is a schematic diagram showing one embodiment of the present invention, and FIGS. 6 to 7 are schematic diagrams showing other embodiments of the present invention. DESCRIPTION OF SYMBOLS 11... Main thyristor, 12a... Commutation capacitor (charging circuit not shown), 12b... Commutation reactor, 12c... Auxiliary thyristor, 13... Diode, 14... Non-linear resistor, 32a-c... Through-hole core.

Claims (1)

[Claims] 1. In a direct current or disconnection device consisting of a diode connected in anti-parallel to the main thyristor, a commutation circuit and a non-linear resistor connected in parallel to the main thyristor, in a parallel circuit between the main thyristor and the non-linear resistor. A direct current or disconnection device characterized in that a saturable reactor formed by passing a conductor through a through-type core such as a ferrite core is connected in series to the main thyristor.