Consequences of having P1000 VFD fed from a motor starter instead of a breaker.

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Besoeker

Senior Member
Location
UK
Gasp! Are you saying that it takes more than one try? My image has been destroyed.:)
We can work on that.........

What if you have to check the motor rotation before coupling to the load..................:)
Ever so slightly more seriously, and I can be from time to time, it's usually to check the correct operation of external controls and indication. Field wiring if you like.
 
I thought that all VFDs required short circuit protection? I had a UL shop sometimes use a motor protector (MP) instead of a 3-pole circuit breaker to save cost, but the motor protector sometimes tripped too easily and had to be replaced with a regular breaker. Since then, on new equipment, I requested to not use a MP. I have had several existing pumps (typically 1 to ~20HP), and then add a VFD to the system that had an existing motor starter and MP (two separate devices) and then use a contact from the motor starer to start the VFD. Again, if the motor protector tripped easily (rarely happened though), then it was replaced with a 3P breaker.
 

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
I thought that all VFDs required short circuit protection? I had a UL shop sometimes use a motor protector (MP) instead of a 3-pole circuit breaker to save cost, but the motor protector sometimes tripped too easily and had to be replaced with a regular breaker. Since then, on new equipment, I requested to not use a MP. I have had several existing pumps (typically 1 to ~20HP), and then add a VFD to the system that had an existing motor starter and MP (two separate devices) and then use a contact from the motor starer to start the VFD. Again, if the motor protector tripped easily (rarely happened though), then it was replaced with a 3P breaker.
Depends on what you means by "Motor Protector". If by that you mean a "Motor Circuit Protector", which is a Westinghouse trade name for a Instantaneous Trip (Magnetic-Only) circuit breaker, then technically, you cannot legally use those in this application no matter what. They are ONLY allowed in a combination motor starter, which can only be used as a motor controller, not a feeder.
 
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