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Project: T174700 #5176

This handbook provides the reader with information for the issues associated with the use of variable frequency drives (VFDs). The handbook also provides a description of the AC motor characteristics when operated at fixed speed from the utility line and when operated by a VFD. The many potential issues upstream and downstream of the VFD are discussed and mitigating solutions are provided. Since the electrical characteristics of the distribution system are different at every site, VFD issues will vary from site to site. There are several system characteristics that can affect how the equipment behaves: a stronger or stiffer utility system allows for larger disturbances to occur before remedial action is needed.

Most motor and VFD issues are known. However, when a series of issues are addressed at one site, the consultant drawings are rarely updated and the same design with the potential issues is provided for the next project. In this report, the reader will find a list of the issues that may be present in their installations. This list can be used by consultants to recommend preventative specifications.


Power quality, Harmonics, Electro-magnetic interference (EMI), VFD motors, VFD cables, Motor filters


This project refers to a number of resource documents that are made available upon request. If you would like a copy of all the documents please email us requesting the zip folder containing these resources.