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Thursday, November 3, 2016

Question:

We have a VFD application. The spec does not indicate the centrifugal pump motor has to be selected as Non-Overloading. Can I use the VFD to limit the pump flow/head conditions that I need for my application using a motor HP that will handle the design conditions and but would not meet a non-overloading condition. I would limit the pump by using the VFD to set a maximum flow/head condition. Appreciate the help.

Larry Gurnari

A

Answer:

Hey Larry thanks for your question. Adjustable Speed Drives are covered by Part X of Article 430. If the drive is marked to indicate that overload protection is provided and a bypass circuit is not used then the drive can provide the overload protection for a single motor as stated in 430.124(A) and (B). Make sure you also follow the drive manufacturer's instructions and the rest of Part X.

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