EMC Performance of Drive Application under Real Load Condition

Since January 1996 all manufacturers have to design their equipment to comply with the protection requirement of the Electro Magnetic Compatibility (EMC) Directive 89/336/EEC of the European Commission. The protection requirement means, that the manufacturer has to minimise the probability of emitting electromagnetic disturbances and of suffering from electromagnetic interference. Manufacturers of Power Drive Systems (PDS) usually define a rated input voltage range, rated power range as well as a climatic ambient within which the PDS has to operate. The EMC product standard EN 61800-3 for adjustable speed electrical PDS [2] accepts light load or unloaded test condition during the conducted emission measurement according to the emission standard EN 55011. In the paper the EMC behaviour of PDS is presented. It is focused especially at the influence of the supply voltage and real load condition on the performance of the input Electro Magnetic Interference (EMI) filter. Investigation shows direct influence of real ambient and load conditions on EMI filter performance. Therefore in many cases passing the EMC tests in laboratory conditions does not mean fulfilling protection requirements in the field.