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V.F.D. calcs #88643 07/02/04 07:41 AM
Joined: Mar 2003
Posts: 849
Y
Yoopersup Offline OP
Member
30 Hp with V.F.D.
430.6 & 430.150
30 hp =40amps at 460 volts
40x150%=60amps
wire size=3#6s &1#10
Disconnect Switch=60amp
Should disconnect switch be up sized to 100 amp (fuseable).Seems to be hitting it right on the mark? wondered if maybe to close??

75hp 460v 3 phase (96 amps)
96x150%=144 amps
wire size=3#1s&1#8
Disconnect switch =100amps

Hows it look guys don;t have into off name plates of VFD so using 430.6c

2017 / 2014 NEC & Related Books and Study Guides
Re: V.F.D. calcs #88644 07/02/04 07:43 AM
Joined: Mar 2003
Posts: 849
Y
Yoopersup Offline OP
Member
Opps Disconnect switch 150 amps not 100 amps

Re: V.F.D. calcs #88645 07/02/04 08:41 AM
Joined: Jan 2003
Posts: 4,391
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iwire Offline
Moderator
Take a look at 430.2.

I do not see an option for using the tables as far as the VFD is concerned.

[This message has been edited by iwire (edited 07-02-2004).]


Bob Badger
Construction & Maintenance Electrician
Massachusetts
Re: V.F.D. calcs #88646 07/02/04 08:52 AM
Joined: Mar 2003
Posts: 849
Y
Yoopersup Offline OP
Member
430.6c
If the maximum operating current does not appear on the nameplate ,the ampacity determinated shall be based on 150% of the valves given in tables 430.149 and 430.150.

Re: V.F.D. calcs #88647 07/02/04 08:57 AM
Joined: Jan 2003
Posts: 4,391
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iwire Offline
Moderator
I do not see that 430.6(C) changes the requirments of 430.2


Bob Badger
Construction & Maintenance Electrician
Massachusetts

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