ESAB Aristo Arc 4000i, Service Manual

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S0740 800 191/E080229/P78
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ct32_15
15AP1:2 Switching circuit
The power module switching components consist of IGBT transistors 15Q1
and 15Q2, operating at a switching frequency of 27 kHz. The transistors must
never be energised when the gate connections are removed.
The gate pulse waveforms and duration are vital for correct operation. See
also page 29.
If an IGBT transistor (15Q1, 15Q2) has failed, both transistors must be
replaced. Failure of either transistor always subjects rectifier bridge 15BR1 to a
high current surge, which substantially reduces its life. We therefore
recommend that the rectifier bridge should also be replaced if the transistors
have failed. See page 58 for instructions on checking the IGBT transistors.
Diode modules 15D1 and 15D2 each contain two diodes. Both they and the
IGBT transistors must be mounted in accordance with the instructions on page
59.
During the time interval between two voltage pulses, the freewheel diode
maintain the welding current from inductor 15L3.
For transient voltage suppression, the bars to the diode modules (15D1, 15D2)
are fitted with two ferrite ring cores each (15L1, 15L2).
15AP1:3 Overvoltage and undervoltage protection
The voltage protection function monitors the voltage across smoothing
capacitors C13--C16. See page 30 for a description of operation.
The voltage protection function is located at the Gate driver board 15AP2, and
powered with 24V from transformer 2TC1.
CAUTION!
Do not mix up contacts B and D on circuit board 15AP2.