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Hi Charlie, On a 3 phase motor that is driven by a VFD, is the disconnect required in section 430.102 B (1) allowed to be omitted as per the exception (a) due to the fact that opening the disconnect while the VFD and motor are under load will cause damage to the VFD? By installing the disconnect between the drive and the motor we are creating an opportunity to cause damage to the drive if opened under load.
Hey Reggie thanks for your question. Yes. The informational Note to 430.102(B) Exception (a) includes motors associated with adjustable drives as an example for not installing a disconnecting means within sight of that motor. The controller disconnecting means must be lockable in accordance with 110.25. Opening a disconnect switch and deenergizing a motor supplied from an adjustable drive without deenergizing the drive can damage the drive.
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ABOUT CHARLIE: Charles M. Trout, better known as Charlie, was a nationally known NEC® expert and author. He served on several NEC® technical committees and is past chairman of CMP-12. In 2006 Charlie was awarded the prestigious Coggeshall Award for outstanding contributions to the electrical contracting industry, codes and standards development, and technical training. Charlie was also a member of NECA’s Academy of Electrical Contracting. Charlie’s experienced team of industry experts keep the CQD dialogue and discussions active and informative in the spirit of the man himself, as he wanted.
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