Danfoss VLT FC 100 Service Manual page 67

Adjustable Frequency Drive ... Service Manual
Stray capacitance between the motor conductors, equipment ground, and other nearby conductors results in induced high
frequency currents.
High ground circuit impedance at high frequencies results in an instantaneous voltage at points reputed to be at ground
potential. This voltage can appear throughout a system as a common mode signal that can interfere with control signals.
These currents return to the DC bus via the ground circuit and a high frequency (HF) bypass network within the adjustable
frequency drive itself. However, imperfections in the adjustable frequency drive grounding or the equipment ground system
can cause some of the currents to travel out to the power network.
5 5
VFD
Motor
AC Line Motor Cable
Stray capacitance
Signal wiring to BMS
Figure 5.3 Signal Conductor Currents
MG94A222 Danfoss A/S © Rev. 2014-02-10 All rights reserved. 65