Chapter 1 Introduction MS300 (High Speed Model) 
 
1-4
1-4 RFI Jumper 
(1)  In the drive there are Varistor / MOVs, which are connected from phase to phase and from phase to 
ground, to protect the drive against mains surges or voltage spikes. 
Because the Varistors / MOVs from phase to ground are connected to ground via the RFI jumper, the 
protection will be ineffective when the RFI jumper is removed. 
(2)  In the models with built-in EMC filter the RFI jumper connects the filer capacitors to ground to form a 
return path for high frequency noise to isolate the noise from contaminating the mains power. 
Removing the RFI jumper strongly reduces the effect of the built-in EMC filter. 
(3)  Although a single drive complies with the international standards for leakage current, an installation 
with several drives with built-in EMC filter can trigger the RCD. Removing the RFI jumper helps, but 
the EMC performance of each drive would is no longer guaranteed. 
Frame B~F       Screw Torque: 4~6 kg-cm / [3.5~5.2 lb-in.] / [0.39~0.59 Nm] 
Loosen the screw and remove the RFI Jumper (as shown below). Fasten the screw again after the RFI 
Jumper is removed. 
 
Frame B~F  (model with built-in EMC filter) 
Remove the RFI Jumper with a screwdriver (as shown below).