ESAB Aristotig 405 AC/DC, Service Manual

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2.3 DIELECTRIC STRENGTH
The three circuits set up for the insulation test are also needed for testing the dielectric strength.
For the dielectric strength test, the standard also specifies how "carefully cleaned, used welding
power supplies shall be tested (e.g. after maintenance or repair without new windings)".
In addition, the design voltage plays a vital role. Systems operating on 400 V 3-phase AC must
be tested to higher specifications than units which can only run on 230 V.
For reasons of simplification, only the higher specifications are given here.
Slowly raise the AC test voltage to full level, apply for 5 seconds, and then reduce to zero. During
the test, the current must not exceed 10 mA. The suppressors may be disconnected during the
test (A15, C6, C7).
AC test voltages:
3 POWER SUPPLY DURING FAULT TRACING
An isolating transformer with voltage and current indication is an ideal power supply to the unit for
fault tracing and start-up after repairs. This is especially the case whenever repairs are carried out
on the primary switches A4, A5, A11, A12. Single-phase design for 0-250 V, 0-4 A is sufficient for
this test.
For systems operating on 3-phase AC only, the voltage must range up to 400 V. A control trans-
former equipped with a 230V/400V auto-winding may be connected on the load side of the isolat-
ing transformer. A supply with the two phases L1 and L2 is adequate for start-up and testing of 3-
phase AC systems at low load.
The isolating transformer offers potential isolation as well as a higher internal resistance. In the
event of faults, the current is limited to levels that are much lower than mains operation. When the
unit is switched on, always raise the voltage starting from 0. This avoids unnecessary follow-on
defects.
Unless major faults have occurred, the unit may remain connected to the mains for fault tracing.
Heed the safety instructions in this Manual.
The other voltages are still applied, i.e. the isolating transformer ranging from 0 to 230 V / 400 V,
the link voltage of up to 620 V, and the derived high-frequency AC voltage. If the power supply
comes from the isolating transformer, never touch any two of these points which are at different
potentials.
Input circuit
→
PE = 565 V
Input circuit
→
Welding circuit = 1500 V
Welding circuit
→
PE = 565 V