Avoiding Electro-Magnetic Interference (EMI)
The inverters are designed to operate in an industrial environment where a high level of
EMI can be expected. Usually, good installation practices will ensure safe and trouble-
free operation. If you encounter problems, follow the guidelines stated below.
Action to Take
Ensure that all equipment in the cubicle is well grounded using short, thick grounding
cable connected to a common star point or busbar
Make sure that any control equipment (such as a PLC) connected to the inverter is
connected to the same ground or star point as the inverter via a short thick link.
Connect the return ground from the motors controlled by the inverters directly to the
ground connection (PE) on the associated inverter
Flat conductors are preferred as they have lower impedance at higher frequencies
Terminate the ends of the cable neatly, ensuring that unscreened wires are as short
Separate the control cables from the power cables as much as possible, using
separate trunking, if necessary at 90º to each other.
Whenever possible, use screened leads for the connections to the control circuitry
Ensure that the contactors in the cubicle are suppressed, either with R-C suppressors
for AC contactors or 'flywheel' diodes for DC contactors fitted to the coils. Varistor
suppressors are also effective. This is important when the contactors are controlled
from the inverter relay
Use screened or armored cables for the motor connections and ground the screen at
both ends using the cable clamps
Safety regulations must not be compromised when installing inverters!
MICROMASTER 420 Operating Instructions