mstrlucky74
Senior Member
- Location
- NJ
do they come with disconnects integral to them? thanks
VFD
- Thread starter mstrlucky74
- Start date
- Status
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
Some offer that as an option on small sizes, yes. Without more info on what you were looking for, that's about all I can offer.
mstrlucky74
Senior Member
- Location
- NJ
Thanks, was just curious if a VFD could act as a disconnect switch.
kwired
Electron manager
- Location
- NE Nebraska
Drive alone can not. Sometimes you get what is similar to a combination starter and you basically get a cabinet with disconnecting means (could be switch only, switch with fuses, circuit breaker) and the motor controller (the drive) as well as other options.
mstrlucky74
Senior Member
- Location
- NJ
Ive seen many times where they show a motor and only a VFD..no disconnect. Maybe then the disco is integral to the motor/equipment.
Normally, on the input we'd have a fuse-switch that can be padlocked in the off position and a contactor on the output. It's also quite common to a disconnect local to the motor also with a padlocking facility.
Unless it is interlocked with the VFD it means you could open it with the motor running. In general VFDs don't like that.
kwired
Electron manager
- Location
- NE Nebraska
Hopefully you have catalog numbers or other data that you can at least research to find more details.
If it is a unit set up for a specific application the chances of it having disconnecting means is probably greater.
If they just give you a catalog number for a naked drive, not only might you need a disconnect you may also need a cabinet to mount it in.
- Location
- Massachusetts
Under the NEC unless an exception applies we are required to provide a disconnect ahead of, and 'in sight from'* the controller. The same applies at the motor location.
If the layout is such that the controller disconnect is also in sight from the motor that controller disconnect can be used to meet both requirements.
Seems similar. Most of what we did was custom build to customer specifications which usually called up a host of their detailed standards. And I mean detailed and often not specifically related to the VSDs.
One had a 40-page section on how to build the wooden packing cases for shipping the VSDs - including an instruction on the correct angle at which to drive the nails in..........
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
This may also be similar to another recent thread in that I see a lot of sloppy drafting when it comes to this as well. On a single line diagram they will just show a box that says "VFD", but leave it unclear as to whether or not a disconnect is needed. I think it's because either they don't care and will simply put in some kind of CYA statement in the project specs making the EC responsible for "meeting local codes", or they put it in the written specs saying that the VFDs must all include a disconnect or circuit breaker and they just didn't want to bother with showing it on the drawings.
The other possibility is that the code allows for remote lock-out at a feeder device even if not within sight under certain circumstances. I've never been a fan of that from a safety standpoint, but it's done a lot to save money.
The other possibility is that the code allows for remote lock-out at a feeder device even if not within sight under certain circumstances. I've never been a fan of that from a safety standpoint, but it's done a lot to save money.
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