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| Electrical Panel Nameplate Values | |||
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| Posted by: Jenny ® 03/22/2007, 10:04:55 Author Profile eMail author Edit |
I have an VFD control panel, 8hp, 460V, 3 phase for main circuit 110V. I am having issues confirming if my calculations reflected for the nameplate. Could some one help explain & confirm the values for the calculated (main circuit) amperage & FLA. Also, what values do I use to figure the Control Circuit amps?
Please help! Further information is available if needed. Thank you so much for your time. Jenny Modified by Jenny at Thu, Mar 22, 2007, 10:05:07 |
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| Re: Electrical Panel Nameplate Values | |||
| Re: Electrical Panel Nameplate Values -- Jenny | Post Reply | Top of thread | Forum |
| Posted by: Bruiser ® 03/23/2007, 22:29:18 Author Profile eMail author Edit |
VFD = variable frequency drive? |
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| Re: Re: Electrical Panel Nameplate Values -- Bruiser | Post Reply | Top of thread | Forum |
| Posted by: Jenny ® 03/26/2007, 07:19:12 Author Profile eMail author Edit |
Yes, 1hp 460V Variable frequency drive |
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| Re: Re: Re: Electrical Panel Nameplate Values -- Jenny | Post Reply | Top of thread | Forum |
| Posted by: Bruiser ® 03/27/2007, 05:12:58 Author Profile eMail author Edit |
I'm guessing at your voltages here, but will include some maths... Normally a VFD nameplate refers to its output capacity. So if you have a 1hp (750W) drive, and 3ph 110V, the output current capacity is I = 750/(1.73*110) = 3.94A. VFDs are often capable of higher currents - up to 2 x for 1s, and say 1.5 x for 10 or 30s. And the 5 x starting current that occurs with direct on line starting won't happen with a vsd - it'll ramp up slowly. As for what it will draw from the mains, and touching on your control power query, assume an efficiency of 0.9. The input power is thus 750/0.9 = 833W, and the input current is 833/(1.73*480) = 1.00A. If I have the input and output voltages reversed, you can swap them back - you'll find the input current to be higher than the output current. Just remember
As a final note, the foregoing neglects power factor and, for the size of motor that you're talking this could be as low as 0.7. Motor efficiency is also quite low for small motors. |
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