JPH01258874A - Thyristor chopper circuit - Google Patents

Abstract

PURPOSE:To execute charging from both directions by short-circuiting the same poles of a couple of polar capacitors and connecting the anodes of a couple of diodes and connecting the cathodes thereof to different poles to form a commutation capacitor and nonpolarizing the polar capacitor. CONSTITUTION:When switches 15 and 24 are turned off, thyristors 14 and 23 are in a nonconductive state and a capacitor 12 is charged from a charging circuit A11 and at the same time, a capacitor 19 is charged from a charging circuit B18. When the switch A15 is then turned on, the thyristor 14 is made in a conductive state and a welding current is supplied to a welding transformer 16 via the thyristor 14 from the capacitor 12. When the switch B24 is turned on after the optional time, the charging voltage of the capacitor 19 is impressed on the cathode of the thyristor 14 and the thyristor 14 is made in the nonconductive state. The welding current carried to the thyristor 14 is then supplied to the welding transformer 16 while charging a capacitor 20 via the thyristor 23. The high voltage is charged on the capacitor 20 in a short time and the voltage is not supplied to the thyristor 23 and the welding current runs out in a short time.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a thyristor chopper circuit that controls supply current using a thyristor chopper.

[Conventional technology]

Conventionally, this type of thyristor chopper circuit has not been used in capacitor spot welding machines, and welding current control using a thyristor chopper has not been performed. FIG. 4 shows a current waveform diagram of a conventional capacitor spot welding machine. Figure 3 is a schematic circuit diagram of a thyristor chopper circuit conventionally used for DC power control. In the figure, (1) is the load, (
2) is the power source that supplies power to this load (1), (3)
is a thyristor that switches the current flowing to the load (1), (4) is switch A that switches the gate current of this thyristor (3), (5) is a commutating capacitor, and (6) is this commutating capacitor. (5)
(7) is a diode that controls the charging and discharging current of the commutating capacitor (5),
(8) is a thyristor which is connected anti-parallel to this diode (7) and switches the commutation circuit, and (9) is a switch B which switches the gate current of this thyristor (8).

Next, the operation of the conventional thyristor chopper circuit based on the above configuration will be explained. By turning on the switch A (4), the gate current of the thyristor (3) flows, the thyristor (3) becomes conductive, and the commutating capacitor (5) is charged at the same time as the current flows to the load (1). By turning on switch B (9), the thyristor (8
) flows, the thyristor (8) becomes conductive, a reverse voltage is applied to the cathode of the thyristor (3), and the thyristor (3) becomes non-conductive.

Next, the commutating capacitor (5) is reversely charged by the back electromotive force of the reactor (6), and the voltage between the anode and cathode of the thyristor (8) is reversed, so the thyristor (8) becomes non-conductive and the load current decreases. Stop.

[Problem to be solved by the invention]

Conventional thyristor chopper circuits are configured as described above, so when introducing them into the discharge circuit of a capacitor spot welding machine, for example, commutating capacitors must be charged in both forward and reverse directions, and non-polar capacitors must be charged. However, if a non-polar capacitor is used, the device becomes larger, and if a polar capacitor is used, the commutation current cannot be cut off in a short time even if commutation occurs.

This invention was made to solve the above-mentioned problems, and it is possible to use a small, large-capacity polar capacitor as a commutation capacitor, and it can also be applied to, for example, a capacitor spot welding machine, where the commutation current can be cut off in a short time. The purpose of this study is to obtain a thyristor chopper circuit.

(Means for Solving the Problems) A thyristor chopper circuit according to the present invention short-circuits the same poles of a pair of polar capacitors, connects the anode poles of a pair of diodes to the short-circuited part, and connects the cathode poles of the diodes to the short-circuited part. are connected to poles different from the short-circuited poles of a polar capacitor, respectively, and are used as commutating capacitors of a thyristor chopper circuit.

[Effect]

The commutating capacitor in this invention is a polar capacitor, but it is made non-polarized by short-circuiting one pole of a pair of polar capacitors and considering both other poles as one capacitor terminal, so that it can be charged from both directions. becomes possible. In addition, it can be made smaller than a non-polar capacitor of the same capacitance.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. Figure 1 is a schematic circuit diagram when one embodiment of the present invention is applied to a capacitor spot welding machine, and Figure 2 (A
), (B), and (C) show each welding current waveform controlled by the thyristor chopper. In FIG. 1, the thyristor chopper circuit applied to the capacitor terminal welding machine according to the present embodiment includes a charging circuit (11) that supplies current to the welding machine (17), and a charging circuit (11) that charges the welding machine from the charging circuit (11). Discharge capacitor (12) that discharges the charged charge
, a diode (13) that prevents a reverse voltage from being applied to the capacitor (12), a thyristor (14) that discharges the charge stored in the capacitor (12), and switching of the gate current of the thyristor (14). a welding transformer (16) that transforms the welding current discharged from the capacitor (12); a welding section to which the welding current transformed by the welding transformer (16) is supplied to perform welding; (17), the above thyristor (14
), a charging circuit (18) that charges the commutation capacitor section (10), electrolytic capacitors (19), (20) and diodes (21), (22), which constitute the commutation capacitor section (lO). Commutation capacitor section (10)
a commutating thyristor (23) that discharges the charge charged in the
The configuration includes a switch B (24) that switches the gate current of the thyristor.

Next, the operation based on the above configuration will be explained.

First, if switch A (15) and switch B (24) are off, thyristor (14) and thyristor (2
3) gate current does not flow, the thyristor (14) and the thyristor (23) are in a non-conducting state, and the charging circuit A (1
Charge is transferred from 1) to the capacitor (12), and the capacitor (12) is charged.At the same time, charge is transferred from charging circuit B (18) to the capacitor (19), and the capacitor (19) is charged.
) is charged. After the necessary charge has been charged, when switch A (15) is turned on, current flows to the gate of the thyristor (14) and the thyristor (14) becomes conductive, passing from the capacitor (12) through the thyristor (14) to the welding transformer. Welding current is supplied to (16). switch A
(15), and after an arbitrary time switch B (24
), a current flows to the gate of the thyristor (23), the charging voltage of the capacitor (19) is applied to the cathode of the thyristor (14), and the thyristor (14)
becomes a non-conducting state. The welding current flowing to the thyristor (14) is supplied to the welding transformer (16) via the thyristor (23) while charging the capacitor (20). Since the capacitor capacity of the capacitor (20) is several tens of minutes lower than that of the capacitor (12), it is charged to a high voltage in a short time, and the voltage between the anode and cathode of the thyristor (23) disappears. This thyristor (23) becomes non-conductive and the welding current is turned off in a short time after turning on switch B (24).

FIG. 2 shows welding current waveforms obtained by arbitrarily changing the time during which switch B (24) is turned on. Second
In Figure (A), switch A (15) is turned on at a, switch B (24) is turned on at lb, switch B (24) is turned on at 2b in Figure 2 (β), and switch B (24) is turned on at 3b in Figure 2 (C). switch B (24) is turned on. By controlling the timing at which switch B (24) is turned on in this manner, the welding current of the capacitor spot welding machine can be cut off at any position.

Furthermore, although the above embodiment describes a thyristor chopper circuit for a capacitor spot welding machine, it may also be used in an inverter circuit for switching direct current, and the same effects as in the above embodiment can be obtained.

〔Effect of the invention〕

As explained above, according to the present invention, the same poles of a pair of polar capacitors are short-circuited, the anode poles of a pair of diodes are connected to this short-circuited part, and the cathode poles of the diodes are connected to the short-circuited part of the polar capacitor. The thyristor is connected to a different pole than the polarized capacitor, and the thyristor is forcibly commutated by the charged charge of the polarized capacitor, so although it is a polarized capacitor, it is non-polarized and can be charged from both directions. It has a certain effect. Further, it has the effect of being smaller in size than a non-polar capacitor of the same capacitor capacity.

[Brief Description of the Drawings] Fig. 1 is a schematic circuit diagram of a thyristor chopper circuit according to an embodiment of the present invention, and Fig. 2 (^), (B), (
C) is a diagram of each welding current waveform of a capacitor spot welding machine output by the circuit in Figure 1, Figure 3 is a configuration circuit diagram of a conventional thyristor chopper circuit, and Figure 4 is a diagram of the welding current output by a conventional capacitor spot welding machine. A welding current waveform diagram is shown. (11), (18)...charging circuit, (12)...
・Discharge capacitor, (13), (21), (22)...diode, (14), (23)...thyristor, (15)
), (24)...Switch, (16)...Welding transformer, (17)...Welding part. In each figure, the same reference numerals indicate the same or corresponding parts. Figure 2 Figure 4 Figure 3

Claims (1)

[Claims] In a thyristor chopper circuit that forcibly commutates a thyristor that switches the power supply supplied from the main power supply, a pair of polar capacitors with the same pole shorted, and a short-circuited part connected in parallel with the capacitor and having the same pole shorted. and an auxiliary power supply connected to the other poles of the pair of polar capacitors other than the short-circuited pole, respectively. A thyristor chopper circuit is connected to an anode and a cathode of a thyristor, respectively, and is characterized in that the thyristor is forcibly commutated by the charge of a pair of polar capacitors.