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Isolation from common DC bus
In case of units with DC voltage remaining: if there are several power sources for the
DC bus, the supply unit which shall be isolated must be equipped with a DC
switch-disconnector (option +F286). In order to isolate the supply unit from the live
DC bus, open the DC switch-disconnector [Q11] and also the charging switch [Q10] in
EVERY cubicle containing supply modules. In addition, open the DC switch-disconnector
of the AC circuit [Q40].
1.
Clearly identify the work location.
2.
Disconnect all possible voltage sources. Note that energy to the DC bus can also
be fed back by motors, energy storages, etc.
•
Make sure that reconnection is not possible. Lock the disconnectors to open
position and attach a warning notice to them.
•
Disconnect any external power sources from the control circuits before you
do work on the control cables.
•
After you disconnect the drive, always wait for 5 minutes to let the
intermediate circuit capacitors discharge before you continue.
3.
Protect any other energized parts in the work location against contact.
4.
Take special precautions when close to bare conductors.
5.
Measure that the installation is de-energized.
•
Use a voltage tester with an impedance of at least 1 Mohm.
•
Make sure that the voltage between the drive input power terminals and the
grounding (PE) busbar is close to 0 V.
6.
Install temporary grounding as required by the local regulations. Connect the DC
busbars to PE with a temporary grounding tool.
7.
Ask for a permit to work from the person in control of the electrical installation
work.
Checking the insulation of the assembly
Measuring the insulation resistance of the drive
￭
WARNING!
Do not do any voltage withstand or insulation resistance tests on any part of
the drive as testing can damage the drive. Every drive has been tested for
insulation between the main circuit and the chassis at the factory. Also, there
are voltage-limiting circuits inside the drive which cut down the testing voltage
automatically.
Measuring the insulation resistance of the input power cable
￭
Before you connect the input power cable to the drive, measure its insulation resistance
according to local regulations.
Electrical installation 47
11
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