Yes. The rules don’t change for the motor circuit. You generally need a disconnect means within sight and not over 50’. There are exceptions, but they have to meet all the rules to the satisfaction of the AHJ. I find it simpler to just put in the disconnect near the motor. It probably means running a control signal from an aux contact of the disconnect Back to the drive.

 

Dozens and dozens of plants, thousands of motors, hundreds of VFDs, no local disconnects. Only local disconnects are on self contained compressors or equipment where the starters are part of the equipment. Met all exceptions though.

 

Its not often you will find an industrial site that lacks lockable buckets which for all intents and purposes are disconnect devices and as there are not local disconnects then you can skip the rules about where to place them. Never seen a 4160 disconnect in the field.

On panels full of starters/vfd's where your options are limited to local disconnects or a complete power down and lock out of the panel i believe that's highly abused.

 

Absolutely. NEC 430.102(B) specifically says a disconnect within line of sight. Memory escapes me but I want to say 8'.

 

And exception...if you have an electrical maintenance staff, not needed!

Now for some pure blasphemy: multiple VFD vendors will threaten you with all kinds of crazy theories about how the VFD will explode or something if you put contactors or disconnects between the VFD and the motor. Well I'm going to plead BS for two reasons. First off those EXACT SAME manufacturers often sell 3 contactor bypasses that do EXACTLY THAT. And they have been running for YEARS with hundreds of water plants with no signs of premature failures at all. And I've never seen any sort of timer delay added to delay between tripping the run signal to the VFD and tripping the output contactor.

Second I HAVE seen safety disconnects fail and explode that are connected to STARTER circuits. As far as I can tell the problem isn't so much disconnecting the load but reconnecting it, and that's when the failures occur. So this particular problem isn't just a VFD issue. But for the normal use, disconnects are there for maintenance purposes and this amounts to the same thing as jerking the cord out of the wall while a vacuum cleaner is running and wondering why the receptacle or the vacuum motor fails prematurely. If you already stopped the motor and open the disconnect without load breaking, there should be no problem at all.

So sure you can go ahead and add an early break aux contact to trip the VFD into coast-to-stop (assuming that is in itself safe). It works just fine and it helps "idiot proof" the system. The same thing can be done with disconnects. In fact I've actually done that with one fine group of utter idiots in New Jersey who insisted that they should be able to do this stuff. But that is pretty much the only time in 30 years that I actually had to add an early break contact and it wasn't even on a VFD but an ordinary starter. By the way those idiots all lost their jobs in the 2009 recession and the plant was turned into a housing development.

 

I wish they would just mandate disconnects on VFD's. I can think of very few circumstances where they aren't needed (I'm sure some of you have those situations). My customer orders all their own equipment, they tried to save a buck on excluding discos on 600A drives. Having to give them the bill for 3 600A discos and the extra labor involved really puckered their pookers. Not to mention all the precious space that was taken up.

 

I'd like to see less disconnects on our sites (ships). Our regs don't require the extras, and ships crew is always present to do proper LOTO. We tend to barely have room for the VFD in the first place, nevermind the disco.