What points need to be noted when using fault current breakers?
In operation of the drive controller, because of the internal suppression capacitors, the high clock frequencies, the parasitic capacitors, the power stage, the motor cable and the RFI suppression filters the leakage current is > 3.5 mA. In individual cases it may be several 100 mA.
The drive controller must therefore always be thoroughly grounded (VDE 0100 part 540, EN 50178) in order to conform to the provisions regarding increased leakage currents applicable above 3.5 mA.
Residual current protective devices (RCDs) must be used in accordance with local regulations. It should be noted, however, that in the event of a fault the drive controller may generate currents with no zero crossing (DC fault currents). Consequently, the drive controllers may only be operated with RCDs of type B for AC fault currents, pulsating and smooth DC fault currents suitable for use with servocontrollers – see IEC 60755. For monitoring functions, residual current monitors (RCMs) can also be used.
RCD = Residual current protective device
RCM = Residual current monitor
