Disconnecting Multiple Motors with One Switch? 3

[JimCook]

I have an application where I need to disconnect and lock out four VFD motors (all are 3 HP) with one switch. But I have been unable to find a suitable switch. Does anyone know of a switch that might work?

This switch is to allow the operator to lock out four sections of belt drivs so that he/she can step out onto the belts to adjust or repair sheets of wood veneer. The operator's switch is only for "minor servicing activities, performed during normal production operations, and are routine, repetitive, and integral to the use of equipment for production."

All motors are independently controlled by their drives. We thought about disconnecting a common power feeder to the drives but the VFDs (A-B 700) would then require too much time to restart. We will have 30A NEMA-style disconnect switches for each motor for servicing the belts or motors.

 

[ScottyUK]

jraef,

Another manufacturer of very good switches is Craig & Derricott - similar to the K&N range but in my opinion of a slightly better build quality. They also make some pretty big multipole switches - 6 poles at over 100A for sure, perhaps bigger than that. I've nothing against K&N, I've used plenty of their stuff too and it is very good.

Jim,

Totally agree about safety relays. They're a great product when applied correctly. My previous comments re. disconnectors / isolators was with respect to making safe for direct contact with conductors, not rendering the machine unable to run which is a very different requirement. Apologies if I misunderstood your aims.


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If we learn from our mistakes I'm getting a great education!

 

[jraef]

Scotty,
C&D looks like a nice line, but not available in the US. They probably don't have UL and don't want to go to the expense.


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[JimCook]

jraef,

My state has had a NRTL excemption for "Industrial Electrical Equipment" in state law for many years. Should I find that the C&D switches will work and they'll ship to us directly, the lack of a NRTL label will not preclude their use in our plants.

 

[jraef]

Really? Usually when they do that it is for when there is no suitable alternative with an NRTL listing, i.e. specialty sensing devices or controllers. I know that's the way it is in all the Western states.

Also check with your insurance company first. Some underwriters put in a clause that has weasel words to the effect of "damage from a fire determined to be caused by a non-evaluated piece of equipment will not be covered."


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> faq731-376

 

[Laplacian]

How about Electro-switch? They build 12 pole switches up to 400A (600VAC), and 6 pole up to 800A (600VAC).

http://www.electroswitch.com/electroswitchesandrelays/default.htm#