SU1215921A1 - Apparatus for a.c.resistance spot welding - Google Patents

Description

The invention relates to contact welding of metals on alternating current and can be used in the manufacture of products of electronic equipment and instrument-making in welding parts requiring connection with a minimum heat-affected zone.

The purpose of the invention is to increase the reliability of the device. ,

The goal is achieved by improving the mode of operation of the key transistors by unplugging their control and switching circuits.

The drawing shows a diagram of the device.

The device contains unit 1 for the number of pulses and pauses, synchronizer 2, unit 3 for controlling current on and off, element 2И 4, power amplifier 5 with transformer output, current limiting resistors 6–9, switches 10 and 11 of equalizing resistors 12–15, The transistors 16-19 and the protective diodes 20 and 21, and the welding transformer 22.

The device keys show the parallel connection of two transistors, but there may be more.

The network voltage goes to synchronizer 2, which produces pulses when the network voltage is zero. From the synchronizer 2, the pulses arrive at the setpoint adjuster 1 of the number of pulses and pauses and the unit 3 controls on and off current. With a permissive control signal

five

0

five

By cycle, the unit 1, the number of pulses and pauses, produces pulses of the weld point or weld, expressed by the number of half-waves of the mains voltage. The control unit 3 generates welding current switching pulses, the leading edge of which determines the switching angle, and the rear edge - the switching angle. The control pulses from setpoint 1 and control unit 3 are sent to element 2I 4. When the signals on it by power amplifier 5 coincide with a transformer output, key start pulses 10 and 11 are generated. The pulse duration determines the open state of keys 10 and 11 and the current flow in welding transformer 22. Amplifier -5 transformer allows the control circuit to be disconnected from the mains voltage.

Regardless of the polarity of the mains voltage, the opening signal from the secondary windings of the transformer amplifier 5 through the current-limiting resistors 6-9 is fed to the transistors 16-19 of both keys 10 and 11. Switching the current from the network through the welding transformer 22 is performed using the keys 10 and 11 and protective diodes 20 and 21. To evenly distribute the switched current between the transistors of the keys, an equalizing resistor 12-15 is included in the emitter circuit of each of them.

Claims (1)

AC CONTROL WELDING DEVICE, containing a synchronizer connected to the input of the number of pulses and pauses and to the input of the control unit for turning the current on and off, the outputs of which are connected to the inputs of element 2I, the output of which is connected through the amplifier to the primary winding of the separation a transformer, the secondary windings of which are connected to the inputs of the first and second transistor switches, each of which is connected between the corresponding terminal of the mains voltage and the corresponding end of the primary windings of the welding transformer, each of the keys consists of parallel-connected transistors, current-limiting resistors in the base and emitter circuits of the transistor switches, characterized in that, in order to increase its reliability, the isolation transformer is equipped with additional windings, each of which is connected to the base junction— emitter of each of the parallel-connected transistors of the first and second keys.