Chapter 1 IntroductionVFD-EL-W
6
RFI Jumper
1. The drive contains Varistors / MOVs that are connected from phase to phase and from phase to
ground to prevent the drive from unexpected stop or damage caused by main surges or voltage
spikes. Because the Varistors / MOVs from phase to ground are connected to ground with the RFI
jumper, removing the RFI jumper disables the protection.
2. In models with a built-in EMC filter, the RFI jumper connects the filer capacitors to ground to form a
return path for high frequency noise in order to isolate the noise from contaminating the main power.
Removing the RFI jumper strongly reduces the effect of the built-in EMC filter. Although a single
drive complies with international standards for leakage current, an installation with several drives
with built-in EMC filters can trigger the RCD. Removing the RFI jumper helps, but the EMC
performance of each drive is no longer guaranteed.
Isolating main power from ground:
When the power distribution system for the drive is a floating ground system (IT) or an asymmetric
ground system (Corner Grounded TN Systems), you must remove the RFI jumper. Removing the RFI
jumper disconnects the internal capacitors from ground to avoid damaging the internal circuits and to
reduce the ground leakage current.
Important points regarding ground connection
Do not remove RFI jumper while the power is ON.
Make sure that main power is OFF before removing the RFI jumper.
Removing the RFI jumper also cuts off the built-in EMC filter capacitors. Compliance with the EMC
specifications is no longer guaranteed.
If you remove the RFI jumper, you remove the reliable electrical isolation. In other words, all controlled
inputs and outputs become low-voltage terminals with basic electrical isolation. Also, when you remove
the internal RFI jumper, the motor drive is no longer electromagnetic compatible (EMC).
Do not remove the RFI jumper if the main power is a grounded power system to make EMC filter
effective
You must remove the RFI jumper when conducting high voltage tests. When conducting a high
voltage test for the entire facility, disconnect the main power and the motor if the leakage current is
too high.
To prevent damage to the drive, you must remove the RFI jumper connected to ground if the AC
motor drive is installed on an ungrounded power system or a high resistance-grounded (greater
than 30 Ω) power system or a corner grounded TN system.
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