Maintenance and testing
Test
Item No.: 099-004833-EWM01
115
7.3.2
Scope of the test
a) Visual inspection
b) Electrical test: measurement of
• open
circuit
voltage
• insulation resistance, or alternatively
• leakage
currents
• protective conductor resistance
c) Functional test
d) Documentation
7.3.3
Visual inspection
The key areas in the test are:
1. Torch/stick electrode holder, welding current return lead clamp
2. Power supply: leads including plugs and strain relief
3. Welding current circuit: leads, plugs and couplings, strain relief
4. Casing
5. Operating, message, safety and adjustment devices
6. Other, general condition
7.3.4
Measuring the open circuit voltage
6u8F
10nF
0...5k
0k2
1k0
1N 4007
Measuring circuit according to DIN EN
60974-1
Connect the measuring circuit to the welding current
sockets. The voltmeter must display mean values and
have an internal resistance
≥
1 M
Ω
. In the case of step
switch controlled devices, set the maximum output voltage
(step switch). Adjust the potentiometer from 0 k
Ω
to 5 k
Ω
during the measurement. The measured voltage should
not deviate from that specified on the rating plate by more
than +/- 5% and may be no greater than 113 V (for devices
with VRD: 35 V).
7.3.5
Measurement of insulation resistance
The mains switch must be on so that the insulation in the interior of the machine can also be checked
through to the transformer. If a mains contactor is fitted, this should be bridged or the measurement must
be carried out on both sides.
The insulation resistance must not be less than:
Mains current circuit
against Welding current circuit and electronics 5 M
Ω
Welding current circuit and
electronics
against Protective
conductor
circuit
(PE)
2.5 M
Ω
Mains current circuit
against Protective conductor circuit (PE)
2.5 M
Ω
7.3.6
Measuring the leakage current (protective conductor and contact current)
Note: Even if the leakage current measurement according to the standard is only an alternative to the
insulation resistance measurement, EWM recommends always performing both measurements,
especially following repair work. The leakage current is based for the greater part on a physical effect
other than the insulation resistance. For this reason, it may not be possible to uncover a dangerous
leakage current using the insulation resistance measurement.
These measurements cannot be performed with a normal multimeter. Even test devices for VDE 0702
(especially older devices) are generally only intended for 50/60Hz. With inverter welding machines,
however, significantly higher frequencies occur, which can interfere with some measuring devices, and
result in others measuring the frequency incorrectly.
A test device must meet the requirements of VDE 0404-2. For the frequency response measurement,
please refer to DIN EN 61010-1 Appendix A – Measuring circuit A1.
For these measurements the welding machine must be switched on and supplying open circuit
voltage.
1. Protective conductor current: < 5mA
2. Leakage current from the welding sockets separately to PE: < 10mA
