Frequency drive as motor control

[slc410]

Does a frequency drive mounted on a wall, not inside a cabinet, need to have external manual start stop buttons. Also, does there need to be short circuit protection upsteam from the drive or does the breaker count as the protection?

 

[kwired]

Short circuit protection is technically to be in accordance with the drive instructions - often expensive fuse types whether really justified or not.

The drive isn't required to have any manual control switches at all, could be completely controlled by other equipment whether digital or analog inputs, or even the operator interface (some don't even have an interface as standard, but often is still an option in those cases)

 

[ptonsparky]

What Kwired says.

Depends.
Yes
Maybe

 

[Jraef]

Short circuit protection is technically to be in accordance with the drive instructions - often expensive fuse types whether really justified or not. ...

Just to further that thought a bit. When a VFD is UL listed, the mfr has a choice of how they want it listed in terms of the upstream Short Circuit Protective Device. Getting a VFD UL listed for any kind of decent amount of SCCR (Short Circuit Current Rating) using a circuit breaker requires destructive testing of the drive WITH the circuit breaker together. Low-end drives meant for the cheap-and-dirty marketplace typically can't afford that expensive testing, so they will opt for listing their drives with current limiting fuses, because they can do a calculated SCCR listing based upon the let-through of the fuses and the withstand capability of the VFD. So that's why kwired said you have to RTFM (Read The F****** Manual) to see what the VFD mfr has had the drive listed with.



F****** = Factory