Worldwel Longrun 25CA, Руководство по эксплуатации

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1) Thyristor and its firing circuit
① Thyristor (Silicon-controlled rectifier)
The thyristor is a semiconductor element with three terminals (anode
, cathode, gate) that can put in any of three states in forward
direction, backward direction and a halted state. When voltage is
applied to the forward direction and a signal is sent the gate, it is
set to the "continuity" state which is maintained until voltage of the
forward direction becomes 0.
② Unijunction transistor (UJT)
It generates the signals needed to fire the thyristor. Phase control of
the firing signal is done by charging the condenser (C1) on the
printer plate with the difference between voltage equivalent to ARC
voltage and the organic voltage of electromotor.
2) ARC voltage control
As explained above, the wire feeding speed that corresponds to a
certain level of ARC voltage is adjusted by a thyristor, and the
phase required to fire signals is controlled by the time to charge a
condenser, that is the difference between the voltage equivalent to
ARC voltage and the organic voltage of the electromotor. Therefore,
in this controller, wire feeding speed is seldom changed by changes
of the load of electromotor. Also, since it is controlled by the
difference between the voltage equivalent to ARC voltage and the
organic voltage of the electromotor, wire feeding speed reacts even
to a small change in ARC voltage, maintaining ARC voltage to be
constant.
3) Anti-stick circuit
It is a circuit that prevents wire to stick to the parent metal after
finishing the welding. After turning the welding stop switch S2 OFF,
it slows turning the point of contact, CR1, OFF and subsequently
slowly turning the magnetic contactor of the welding power supply
OFF.