System Design of Adjustable Speed Drives, Part 2: System Simulation and ac Line Interactions

Part 1 of System Design of Adjustable Speed Drives [1] investigated the second-order effects that occur as interactions between adjustable speed drives (ASDs) and system-connected equipment, specifically with regard to commonmode (CM) voltage and ground noise current injected in the system and differential-mode (DM) voltage spikes on the load due to ASD semiconductor switching [1]. This article (Part 2) continues the investigation by proposing high-frequency ASDs, cable, and motor models used in system simulation to identify and mitigate the complex DM or CM injected. Theoretical component models were bridged with field experience to simulate and resolve a practical low-voltage (LV) field example of parallel high horsepower inverters having instantaneous overcurrent (IOC) trip issues due to circulating CM currents between inverters and ground. Component models are also used in a system electromagnetic interference (EMI) simulation example of a power structure, which induced line-to-ground noise current in an industrial plant ground grid.