VSD local disconnect

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gabany

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can anyone give me a true reason a stand alone VSD needs a disconnect within site? I am talking small (480 - 230VAC less than100hp) VSDs.
In an industrial facility, drives may be located outside the electrical room (to minimize the drive to motor feeder length or simply space constraints).
I see no benefit to this, other than the Electrician or Engineer not having to walk back to the MCC to lock it out!
Having a disconnect within site of the motor does make sense to me, however this requirement can be "excepted" by having a lockable disconnecting means in a remote location. So why not the same exception for the controller (aka VSD)??
Thanks.
 
Re: VSD local disconnect

The NEC requires a disconnect for the motor and a disconnect for the controller. Two different animals two different requirements.
 
Re: VSD local disconnect

a Variable Speed Drive (VSD) is a controller. I am asking why NEC 430.102(A) requires a disconnect to be located within sight of it.
 
Re: VSD local disconnect

I suppose for the same reason that the code requires a local disconnect for other types of motor controllers. It is to permit maintenance with the technician being able to visually verify that the circuit has been de-energized (i.e., he can see if anyone is about to close the disconnect switch).
 
Re: VSD local disconnect

could be that the manufacturers of disconnect switches were over represented in the code making process.

:)
 
Re: VSD local disconnect

My 2 cents: It's just too tempting to shut off the VSD (or controller) and work on the motor without going back to lock out the disconnect in the MCC room.

But if there is a disconnect at the controller, it is just as easy to shut off the disconnect as it is to turn off the controller.

Steve
 
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