EMI Emissions of Modern PWM ac Drives

Electromagnetic Interference (EMI) noise is defined as an unwanted electrical signal that produces undesirable effects in a control system, such as communication errors, degraded equipment performance and malfunction or non-operation. References on the general principles of EMI are available [l]-[3], as well as methodologies on calculating radiated emissions [4]. IEEE Standard 518 applied these principles to slow switching Silicon Controlled Rectifier (SCR) dc drives in 1982 [5]. All ac Pulse Width Modulation (PWM) drives have the potential to cause EMI with adjacent sensitive equipment, when large quantities of drives are assembled in a concentrated area [6]-[11]. However, faster switching speeds of new converter/inverter topologies require an updated study of new system EMI issues created.