Avoiding Electro-Magnetic Interference - Siemens MICROMASTER 420 Getting Started Manual

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Avoiding Electro-Magnetic Interference

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.
Actions 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 connected to the inverter (such as a
PLC) is connected to the same ground or star point as the inverter via a
short, thick link
Connect the return ground from the motors, 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 as possible
Separate the control cables from the power connections as much as
possible, using separate trunking, if necessary at 90
Whenever possible, use screened leads for the connections to the control
circuitry
Ensure that contactors inside 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 connections for the motor connections and ground
the screen at both ends using cable clamps
Warning
!
Safety regulations must not be compromised when
installing inverters!
Getting Started Guide – September 2000
6SE6400-5AB00-0BP0
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right angles.
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