Fuji Electric FRENIC-Ace series, User Manual

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Appendix C Effect on Insulation of General-purpose Motors Driven with 400 V Class Inverters
Appendix-20
C.4 Regarding existing equipment
[ 1 ] In case of a motor being driven with 400 V class inverter
A survey over the last five years on motor insulation damage due to the surge voltages originating from switching of
inverter elements shows that the damage incidence is 0.013% under the surge voltage condition of over 1,100 V
and most of the damage occurs several months after commissioning the inverter. Therefore there seems to be little
probability of occurrence of motor insulation damage after a lapse of several months of commissioning.
[ 2 ] In case of an existing motor driven using a newly installed 400 V class inverter
We recommend suppressing the surge voltages with the methods shown in “C.3 Countermeasures against surge
voltages”.