Siemens 420 manual Avoiding Electro-Magnetic Interference EMI, Action to Take

2 Installation Issue 07/04

2.4.4Avoiding 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!

MICROMASTER 420	Operating Instructions
32	6SE6400-5AA00-0BP0