ESAB Powercut 1600 Service Manual page 81

SECTION 4 DESCRIPTION Of OPERATION
4.10.16 Power Board_PCB2 Filter Buss/IGBT (0558038315)
When the converter is on, the IGBT circuit delivers an 18.5 KHz AC power to the main transformers. The
IGBTs are gated on by signals from the driver boards and regulate the output of the PC 1600 (see Section
4.10.21).
Some filter capacitors hold charges for long periods of time. Charged capacitors can present a shock
hazard. It is not safe to assume the capacitors have been drained even if there is a bleeder resistor across
them. Technicians who work with high voltage supplies use a shorting rod or a shorting stick to be certain
that all the filters are drained before working on the equipment. High-energy capacitors can discharge vio-
lently, so it is important that the shorting rod contain a high- wattage resistor of around 20 ohms to keep the
discharge current reasonable.
The filter caps are configured in two different ways in the PC1600 230/460 model, dependant upon the in-
put voltage. The power selector switch S3 will place the four filter capacitors in either a series configuration
or in a parallel pair configuration.
In the 460 VAC mode of operation, the four capacitors are placed in series – all four capacitors connected
in a daisy chain, each capacitor dropping 162.5 VDC. (See Section 4.10.16 "Series connected")
In the 230 VAC mode of operation, the four capacitors are divided up into two pairs. Each pair has two ca-
pacitors in series and then the pairs are placed in parallel with one another. (See Section 4.10.16 "Parallel
connected") again each capacitor supplying 162.5 VDC.
4.10
In 400 VAC and 575 VAC units, the capacitors are in series. There is no power selector switch in the 400
VAC or the 575VAC units.
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