Danfoss VLT FC 100 Service Manual page 68

Adjustable Frequency Drive ...
Unprotected or poorly routed signal conductors located close to or in parallel to motor and line power conductors are
susceptible to EMI.
Signal conductors are especially vulnerable when they are run parallel to the power conductors for any distance. EMI
coupled into these conductors can affect either the adjustable frequency drive or the interconnected control device. See
Figure 5.4.
While these currents tend to travel back to the adjustable frequency drive, imperfections in the system cause some current
to flow in undesirable paths thus exposing other locations to the EMI.
5 5
AC Line
Figure 5.4 Alternate Signal Conductor Currents
High frequency currents can be coupled into the line power supplying the adjustable frequency drive when the line power
conductors are located close to the motor cables.
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Service Manual
VFD
Motor Cable
Danfoss A/S © Rev. 2014-02-10 All rights reserved.
Motor
Stray capacitance
AC Line
MG94A222