Chapter 4—Safety and Switching
DG1 Series VFD MN040002EN—March 2014 www.eaton.com 17
Safety-relevant leakage currents can occur while handling
and when operating the frequency inverter, if the frequency
inverter is not grounded (because of a fault).
Leakage currents to ground are mainly caused by foreign
capacities with frequency inverters, between the motor
phases and the shielding of the motor cable and via the
Y-capacitors of the RFI filter. The size of the leakage current
is mainly dependent upon the:
●
length of the motor cable
●
shielding of the motor cable
●
height of the switching frequency of the inverter
●
design of the RFI filter
●
grounding measures at the site of the motor
The leakage current to ground is greater than 3.5 mA with a
frequency inverter. According to product standard IEC/EN
61800-5-1, an additional equipment grounding (PE) conductor
of the same cross-sectional area as the original protective
earthing conductor must be connected, or the cross-section
of the equipment grounding conductor must be at least
10
mm
2
Cu.
Residual current circuit breakers must be suitable for:
●
the protection of installations with DC current component
in case of fault scenario (RCD type B)
●
high leakage currents
●
brief discharges of pulse current spikes
Input Contactor
The input contactor enables an operational switching on and
off of the supply voltage for the frequency inverter, and
switching off in case of a fault.
The input contactor is designed based on the input current
(ILN) of the frequency inverter and the utilization category
AC-1 (IEC 60947). Input contactors and the assignment to
DG1 frequency inverters are explained in Appendix A.
While planning the project, make sure that inching operation
is not done via the input contactor of the frequency inverter
on frequency-controlled drives, but through a controller input
of the frequency inverter.
The maximum permitted operating frequency of the input
voltage with the DG1 frequency inverter is one time per
minute (normal operation).
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