VFD as a dsiconnect

[anbm]

Do we consider VFD as a disconnect? i.e. we can shut down power to motor from its VFD? Anyone has any articles about this will helps. Thanks!

 

[Jraef]

In the US, no. The requirements of LOTO make it necessary to have an air gap that physically removes power.

In IEC world, some drives have a safety rating that qualifies as "safe mode" with regards to machine safety, but even then I'm not sure it is considered safe in terms of working on the VFD itself.

 

[mcclary's electrical]

Jraef, what if it's a stand alone drive, with a lockable handle on the front that references upas on,and down as off, and that, via linkage, disengages a breaker inside the drive??

 

[Cmdr_Suds]

I am going to assume you have a VFD inside a larger enclosure that has a breaker inside. The breaker inside the drive cabinet would be considered your service disconnect and fault current protection. The drive itself is the motor controller and normally provides overload current protection.

 

[Jraef]

I did not assume there was a disconnect or breaker involved, hence the original question. If there is a disconnect or breaker, then of course that meets the requirements.

 

[anbm]

Will it cost less if we buy and install disconnect/CB and VFD separately?

 

[weressl]

Jraef, what if it's a stand alone drive, with a lockable handle on the front that references upas on,and down as off, and that, via linkage, disengages a breaker inside the drive??

You are talking about a 'packaged drive' not an ASD which normally does not have a means of disconnect. A packaged drive with either an MCB or a fused disconnect with an externally operable and padlockable handle would certainly qualify as a means of disconnect.

I love these posts where a question is asked and the full details emerge later......:roll:

 

[weressl]

Will it cost less if we buy and install disconnect/CB and VFD separately?

Depends on the installation. If your conditions permit the means of disconnect not to be 'within sight' then your feeder most likely have a means of disconnect that could qualify as such. Even in the case of local enclosed disconnect and bare NEMA 1 drive would be somewhat cheaper than the 'packaged drive'.

 

[Besoeker]

FWIW the first line in our specs for a variable speed drive is usually like this:
1 off input 3-pole door interlocked OS 160 B3 G1 fuse switch, padlockable in the off position.

This is a common UK customer requirement.