Siemens MICROMASTER 420 - Manual (Page 32)

2 Installation Issue 07/04
MICROMASTER 420 Operating Instructions
32 6SE6400-5AA00-0BP0
2.4.4 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 as possible
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
WARNING
Safety regulations must not be compromised when installing inverters!