JPH0724950Y2 - Transistor converter - Google Patents

Description

[Detailed Description of the Invention] [Field of Use in Work] The present invention relates to a transistor converter.

[Conventional technology]

FIG. 2 is a circuit diagram showing a conventional example of a transistor converter. In the figure, reference numeral 1 is a converter (AC-AC) in which six transistors, that is, positive side arm transistors 2 _RP , 2 _SP and 2 _TP , and negative side arm transistors 2 _RN , 2 _SN and 2 _TN are bridge-connected. In the main circuit of the DC converter), each transistor 2 _RP , 2 _SP , 2 _TP , 2 _RN , 2 _SN , 2 _TN has a diode 3 connected in anti-parallel, and outputs between DC output terminals P-N. A voltage smoothing capacitor 4 is inserted. 5 _R , 5 _S and 5
_T indicates a three-phase AC input terminal. In each phase of the AC input circuit, a reactor 6 for smoothing an input current, a contact 7 and an inrush current preventing current limit connected in parallel with the contact 7 are provided. The resistor 8 is inserted.

Before the start of operation, the contacts 7 of each phase R, S, T are opened,
All of the six transistors 2 are off and the capacitor 4 is in a non-charged state. In this state, when 3-phase AC is applied to the 3-phase AC input terminals 5 _R , 5 _S and 5 _T to start up,
Six diodes 3 operate as a three-phase full-wave rectifier circuit,
The output charges the capacitor 4. Since this capacitor charging current flows through the current limiting resistor 8, an excessive inrush current is prevented from flowing during this initial charging. At this time, although not shown, the power supply from the DC terminal P-N to the load is cut off. When the initial charging of the capacitor 4 is completed, the contactor 7 is turned on, whereby the current limiting resistor 8 is bypassed, and then each transistor of the main circuit of the converter 1 is on / off controlled in a predetermined operation sequence.

[Problems to be solved by the invention]

In this type of converter, when a power failure occurs during normal operation, the contactor 7 is opened in response to the power failure detection operation of the power failure detection unit (not shown), and the output of the transistor drive circuit (not shown) is turned on or off. However, in the transistor converter of FIG. 2, the AC input circuit has a current limiting resistor 8 for limiting the inrush current, and after the initial charging of the capacitor 4, the current limiting resistor 8 is short-circuited by the contactor 7. Therefore, when an instantaneous power failure occurs for a time shorter than the operation delay time of the contactor 7, power may be restored before the contactor 7 is opened. However, there is a problem that the main circuit parts are damaged or the overcurrent relay operates to power on or disconnect the switch unnecessarily.

This invention was made to solve the above problems,
An object of the present invention is to provide a transistor converter that can prevent the inrush current of charging even when power is restored after a momentary power failure.

[Means for solving problems]

In order to achieve the above object, the present invention inserts a current limiting resistor in series with a DC output circuit, and connects a bypass circuit in which a thyristor and a diode are connected in anti-parallel in parallel to the current limiting resistor to connect the thyristor to the The configuration is such that the converter is forcibly turned on during operation of the converter.

[Action]

In this invention, if there is a current limiting circuit in the DC output circuit and there is an instantaneous blackout, the thyristor bypassing the current limiting resistance will self-extinguish when the stored energy of the reactor is released after turning off the transistor. As compared with the case where the current limiting resistor is short-circuited / released from the short-circuiting by the contactor, the short-circuiting of the current limiting circuit can be released promptly.

〔Example〕

FIG. 1 is a circuit diagram showing an embodiment of the present invention.
The current limiting resistor 8 is inserted in series to the DC output circuit of the main circuit of the transistor converter 1, and the circuit in which the thyristor 9 and the diode 10 are connected in anti-parallel is connected in parallel to the current limiting resistor 8, 2 is different from that shown in FIG. 2 in that a current limiting circuit is not provided in the AC input circuit. The other structure is the same as that of FIG. 2 described above, and therefore is shown with the same reference numerals.

Before operation, 6 transistors 2 _RP , 2 _SP , 2 _TP , 2 _RN , 2
_SN , 2 _TN and thyristor 9 are off and capacitor 4 is uncharged. In this state, 3-phase AC input terminal
When three-phase alternating current is applied to 5 _R , 5 _S, and 5 _T to start up, the six diodes 3 operate as a full-wave rectifier circuit, and the output charges the capacitor 4. Since this capacitor charging current flows through the current limiting resistor 8, an excessive inrush current is prevented from flowing during this initial charging. At this time, although not shown, the power supply from the DC terminal P-N to the load is cut off. When the initial charging of the capacitor 4 is completed, a gate signal is supplied to the thyristor 9 and
The transistors 2 _RP , 2 _SP , 2 _TP , 2 _RN , 2 _SN and 2 _TN are on / off controlled in a predetermined operation sequence, and the current limiting resistor 8 is short-circuited by the thyristor 9 and the diode 10. The diode 10 connected in anti-parallel to the current limiting resistor 8 is a transistor
This is for freely flowing a regenerative current (instantaneous regenerative current included in the ripple current, that is, a leftward current in the drawing) from the capacitor 4 to the full-wave rectifier circuit side during normal operation of the converter 1.

When an instantaneous power failure occurs in the AC power supply, the transistors 2 _RP , 2 _SP , 2 _TP , 2 _RN , 2 will respond in response to the operation of the power failure detection unit (not shown).
_SN and 2 _TN are cut off. By stopping the operation of this transistor, the current flowing in the transistor, for example, the transistor 2 _RN through the reactor 6, is transferred to the diode 3 in the opposite arm and flows through the thyristor 9. Therefore, when the gate signal to the thyristor 9 is cut off after the base signal to each transistor is cut off, the thyristor 9 disappears due to the disappearance of the current transferred to the thyristor 9.
Self-extinguishes. This current is attenuated in a time much shorter than the operation delay time of the contact 7 because the inductor 6 has a small inductance.

Therefore, according to this embodiment, before the power recovery, the thyristor 9
Can be self-extinguished, and the rush current flows through the current limiting resistor 8 when the power is restored, so that the main circuit components of the converter 1 are prevented from being damaged by the rush current.

Although this embodiment is a converter which inputs three-phase alternating current, the present invention can be applied to the case of a single phase.

[Effect of device]

As described above, according to the present invention, the DC output circuit of the conventional transistor converter is provided with the current limiting resistance, and the current limiting resistance is bypassed by the circuit composed of the thyristor and the diode in antiparallel thereto. Even if there is a momentary power failure, the short circuit of the current limiting resistor can be promptly solved, and it is possible to avoid delaying the short circuiting of the current limiting resistor until the power is restored. It is possible to prevent the inrush current from flowing in and damage the main circuit components, and it is possible to improve reliability and stability as compared with the conventional case.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a circuit diagram showing a conventional transistor converter. In the figure, 2 _RP , 2 _SP , 2 _TP , 2 _RN , 2 _SN , 2 _TN ... Transistor, 4 ... Capacitor, 6 ... Reactor, 8 ... Current limiting resistance, 9 ... Thyristor, 3, 10 ... …diode. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of utility model registration request] 1. A transistor converter in which a plurality of transistors are bridge-connected and each transistor is connected in parallel with an element for permitting reverse conduction, and a smoothing capacitor is provided between DC output terminals of the transistor converter. A current limiting resistor is inserted in series, a bypass circuit in which a thyristor and a diode are connected in anti-parallel is connected in parallel to the current limiting resistor, and the thyristor is forcibly turned on during operation of the converter. Transistor converter.