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PSU 5000 / PSG 3000
Connection
Instructions for Assembly and Operation
11.6 Protective conductor connection to medium ---frequency transformers
BOSCH medium--frequency transformers comply with protection class 1 in accor-
dance with DIN VDE 0551 Part 1.
For protection class 1, additional protective measures must be applied in accor-
dance with EN 50063 (DIN VDE 0545, Part 1) to provide protection against inad-
missibly high contact voltages in the event of an insulation breakdown between the
primary and the secondary circuit. The implementation of these measures is the
responsibility of the machine/plant manufacturer/operator.
If these protective measures are not applied, or if they are ineffective, touching the
secondary connections, the welding gun or the workpiece is associated with dan-
ger of life and limb!
When delivered, a detachable protective conductor jumper (MPE) is connected be-
tween the secondary circuit (negative pole) of the medium--frequency transformer
and the transformer's protective conductor connection. This is in compliance with
the protective measure "direct protective conductor connection" to EN 50063, Sec-
tion 5.1.4.1.
If another protective measure to EN 50063 is implemented instead of "direct pro-
tective conductor connection", the protective conductor jumper (MPE) must be re-
moved.
The removal of the protective conductor jumper (MPE) must be indicated on the
label provided on the transformer in a permanent way.
As an additional measure for achieving protection class 1, the housing of the me-
dium--frequency transformers is permanently connected to the protective conduc-
tor connection of the transformer. This connection cannot be removed.
ATTENTION!
Under certain circumstances (cf. NOTE section), circulating currents ("crossover
!
currents" to EN 50063) can flow through the MPE protective conductor connection.
These circulating currents must be avoided under any circumstances because
they may interrupt the protective conductor continuity through the protective con-
ductor jumper (MPE).
Interrupting the protective conductor connection will render the protective measure
"direct protective conductor connection" ineffective. Therefore, in the case of an
insulation breakdown there is danger of life!
1070 078 224- -109
11--11
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