Incorrectly installed VFDs can cause high levels of high frequency stray currents to flow through the metalwork attached to the motor. These stray currents can cause interference with other electrical and electronic equipment. For more information, see
Even correctly installed drives can give you plenty of EMI, That is what thyristors do. Can poor installation make things worse? You bet!
Yes, agreed but just what constitutes a correct installation? I am often called in to sort EMC issues on correctly installed VFDs to find that the screen is terminated at one end only and/or pigtails are used. Eliminate pigtails and you can reduce the level of noise by a significant amount.
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