Bosch PSU 5000 Series Instructions For Assembly And Operation Manual page 94

How to measure circulating currents
Supply line
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U
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V
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PE
Remedying circulating currents
1070 078 224- -109
PSU 5000 / PSG 3000
Instructions for Assembly and Operation
Transformer
Rectifier
MPE
Housing
A welding current meter for measuring DC current is required for measuring the
circulating currents.
(1) Apply measuring belt to positive pole of the electrode gun and fix its position.
Close the electrode gun without a workpiece, apply welding current (MF inverter
in current control mode). Measure and record welding current I
(2) Close the welding gun with the workpiece, close "neighboring gun", if any,
(Case 4), apply welding current with current specification as described
under (1).
Measure and record welding current I
If the current values are different, the presence of circulating currents has to be
assumed. The amount of the circulating current is calculated as I
circulating current.
If circulating currents cannot be avoided by the protective measure "direct protec-
tive conductor connection", other protective measures to EN 50063 must be
installed by the machine/plant manufacturer/operator.
For example, protective measures such as current--operated e.l.c.b. systems or
voltage--operated e.l.c.b. systems (cf. EN 50063, Sections 5.1.4.3 and 5.1.4.4)
may be installed for medium--frequency systems.
However, it must be noted that the equipment used for the measures described
above must be suitable for operation with medium--frequency systems with a DC
link circuit and a frequency of 1000 Hz. The manufacturer's specifications must be
verified accordingly. The applicable standards are to be observed.
(1)
+
- -
Welding
current meter
.
(2)
Connection
(2)
+
Workpiece
- -
A
.
(1)
-- I = approx.
(2) (1)
11--15