2 Engineering
2.4 Safety and switching
DC1…20… and DC1…OE1 Variable Frequency Drives
02/20 MN040059EN
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2.4.3 Residual current circuit-breaker (RCD)
When using variable frequency drives (DC1-
3
…) that work with a three-
phase power supply (L1, L2, L3), make sure to use type B AC/DC sensitive
residual current devices exclusively.
When using variable frequency drives that work with a single-phase power
supply (L, N) (DC1-
1
2… and DC1-1D…), you may use type A and type B
residual current protective devices (RCD).
The leakage currents’ magnitude will generally depend on:
•
length of the motor cable
•
shielding of the motor cable
•
height of the switching frequency (switching frequency of the inverter),
•
design of the radio interference suppression filter
•
grounding measures at the site of the motor.
Other protective measures against direct and indirect contact can be used for
DC1 variable frequency drives, including isolating them from the supply
system with the use of a transformer.
2.4.4 Overvoltage protection
If overvoltage are to be expected in the network or if normative specifi-
cations at the place of use require the same, an additional overvoltage
protection must be implemented.
To comply with UL conformity, the surge protection must be installed on
the mains side of the device. It must be designed for 480 V (“phase to
ground”) and 480 V (“phase to phase”), must also be suitable for overvoltage
category III and have a protection level of 4 kV.
NOTICE
Residual current circuit-breakers (RCD = residual current device)
should only be installed between the power feed system (the AC
supply system supplying power) and the DC1 variable frequency
drive – but not at the output to the motor!
