Harmonics & Vfds: Prevention, Analysis, Resolution

摘要

Keith Lane: VFDs can reduce the starting inrush current and kVA to half of that of an across-the-line starter. The reduction of inrush current in an electrical distribution system has a number of advantages. Many utilities require some form of reduced voltage starting for all motors over 25 hp. On the downside, VFDs utilize silicon controlled rectifiers to chop up the ac waveform and will provide a nonlinear waveform. This nonlinear waveform will cause voltage distortion across the reactor of the generator or the utility transformer and can cause unacceptable transient performance. This will adversely affect the performance of the entire electrical system.