Principal Diagram Dtg 405 - ESAB DTG 405 Service Manual

PRINCIPAL DIAGRAM DTG 405

The DTG 405 is a primary-switched power unit, using a forward asymmetrical half-bridge
switched mode power supply (A4, A5, A11, A12). A high frequency transformer (T3) isolates the
mains potential (L1, L2, L3) from the welding potential. After high frequency rectification (A4, A5,
A11, A12) the polarity of the output current is controlled by an AC converter (A9, A10, A13, A14,
full-bridge topology). Inductor L1 smooths the current and stores switching energy.
The primary switching frequency is about 66 kHz (pulse-width-modulation, PWM). The frequency
of the welding current while AC-welding is controlled from 50 Hz to 200 Hz by the AC converter.
The AC converter has four MOSFET switches. If no control signal is applied, all switches are
turned off. No output current is possible. During normal operation there are control signals in ei-
ther forward polarity (two switches are on and two are off) or in reverse polarity.
A high voltage ignition unit (A7) is used for ignition and stabilising the arc while welding.
DTG 405f.pcx
X3 is connector to TIG-torch, X7 is connector to stick holder, X2 is connector for workpiece cable.
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