adj speed drive and branch ckt protection?

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ae1dpg

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I have a application on an industrial machine where a 200hp ASD is being used w/ a 100hp motor. The existing branch circuit protection is sized according to motor (fusing @ 175%FLA, wiring @ 125%FLA, and disconect @115%FLA). The reason for the 200hp drive is due to service factor motor is used at.
My question would be if the existing protection is properly rated to handle motor HP, should it stay as is or change based on ASD HP rating???
 
Re: adj speed drive and branch ckt protection?

ae1dpg,

Your goal is to protect the motor that you are using,100hp.

No different than a 15a circuit in a 30a disconnect.JMO
 
Re: adj speed drive and branch ckt protection?

In this case the circuit supplying the speed drive must be sized on the 200 HP rating of the drive, that does not change if the motor is 200 or 2 hp.

430.2 Adjustable-Speed Drive Systems.

The incoming branch circuit or feeder to power conversion equipment included as a part of an adjustable-speed drive system shall be based on the rated input to the power conversion equipment. Where the power conversion equipment is marked to indicate that overload protection is included, additional overload protection shall not be required.
The disconnecting means shall be permitted to be in the incoming line to the conversion equipment and shall have a rating not less than 115 percent of the rated input current of the conversion unit.
Click to expand...
The conductors from the speed drive to the motor can be sized based on the motor HP.

[ January 02, 2006, 04:31 PM: Message edited by: iwire ]
 
Re: adj speed drive and branch ckt protection?

Originally posted by benaround:
That's why you make the big bucks,thanks.
Click to expand...
Thanks but truth be told I will never forget 430.2 as a couple of years ago I answered the same question very much like you did here. :eek:
 
Re: adj speed drive and branch ckt protection?

Just a quick motor theory question.
If I recall, when a motor runs into its service factor range, its full load current is more than FLA.
Service factor is a multiplier that is applied to the motor?s normal horsepower rating to indicate an increase in power output (or overload capacity) that the motor is capable of providing under certain conditions.
Click to expand...
What is the amperage that the 100HP motor will draw when operating at it's high service factor? Common values of service factor are 1.0, 1.15, and 1.25.
Constant runs into service factor will severely reduce the motor's lifetime.

[ January 02, 2006, 04:49 PM: Message edited by: ron ]
 
Re: adj speed drive and branch ckt protection?

which two oh wanabe? Is that pronounced "wuh nah bee"? Ahdiy Wanabee, the venerable one! :D

paul
 
Re: adj speed drive and branch ckt protection?

ron,

The service factor amps may not be an actual value of (NP*S.F.) I have seen S.F. amps listed on the motor nameplate and had to call the motor manufacture to get them and they have been <,>, and = (NP*S.F.). I do not agree that constant runs of the motor into the service factor will severely reduce the motor's life. IMO, the main factor is winding temperature not just running amps. A motor operating above rated temperature rise will fail prematurely regardless of running above or below service factor.
 
Re: adj speed drive and branch ckt protection?

Tony,
High running amps (service factor operation) would most likely be associated with high winding temperature, thus reduced lifetime.
 
Re: adj speed drive and branch ckt protection?

Bob,

I appreciate the response w/ NEC code section, I had read and figured that would be the way. Just seems overkill, considering motor load will never exceed input rating of drives.
Do you know, or anyone else reading this post, if NEC 2005, with new section X for ESD's, indicates anything more specific??

Thanks :)
 
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