Siemens MICROMASTER 440 Operating Instructions Manual

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2 Installation Issue 10/03MICROMASTER 440 Operating Instructions42 6SE6400-5AW00-0BP02.4.4 Avoiding Electro-Magnetic Interference (EMI)The inverters are designed to operate in an industrial environment where a highlevel of EMI can be expected. Usually, good installation practices will ensure safeand trouble-free operation. If you encounter problems, follow the guidelines statedbelow.Action to Take¾ Ensure that all equipment in the cubicle is well grounded using short, thickgrounding cable connected to a common star point or busbar¾ Make sure that any control equipment (such as a PLC) connected to theinverter is connected to the same ground or star point as the inverter via a shortthick link.¾ Connect the return ground from the motors controlled by the inverters directly tothe ground connection (PE) on the associated inverter¾ Flat conductors are preferred as they have lower impedance at higherfrequencies¾ Terminate the ends of the cable neatly, ensuring that unscreened wires are asshort as possible¾ Separate the control cables from the power cables as much as possible, usingseparate trunking, if necessary at 90º to each other.¾ Whenever possible, use screened leads for the connections to the controlcircuitry¾ Ensure that the contactors in the cubicle are suppressed, either with R-Csuppressors for AC contactors or 'flywheel' diodes for DC contactors fitted to thecoils. Varistor suppressors are also effective. This is important when thecontactors are controlled from the inverter relay¾ Use screened or armored cables for the motor connections and ground thescreen at both ends using the cable clampsWARNINGSafety regulations must not be compromised when installing inverters!2.4.5 Screening MethodsFrame Sizes A, B and CFor frame sizes A, B and C the Gland Plate Kit is supplied as an option. It allowseasy and efficient connection of the necessary screening. See the Gland PlateInstallation Instructions contained on the Document CD-ROM, supplied with theMICROMASTER 440.