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Associate

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### Power Consumption

04/29/2012 1:48 AM

There guys,

Please tell how this three terms relates with each others and how can i use it for wire size computation especially only one or two are mentioned. Is there a formula that connects the three?

1. KVA - power consumption

2. KW - power

3. Amperes - full load current

I have some ideas but i need a concrete one because i am always confused.

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#1

### Re: power consumption

04/29/2012 8:59 AM

Sigh. Did you at all even try to look up the electrical definition of KVA to amps. If you had you'd notice that KVA is a measurement of apparent power. Apparent power is a magnitude sum in quadrature of real power (KW) and reactive (imaginary) power. Now once you are capable of defining, calculating or measuring the apparent power a circuit will draw from a voltage source then you can identify the magnitude of the current that will flow through your wires. The magnitude of the current flowing through your wires will set a minimum wire thickness your wires must be to prevent catastrophic self heating from Joule heating.

Now I cannot clarify your confusion on these topics by just handing you an answer. You must do some of your own homework or the concept will never sink in. If you follow the links I've provided and study them but still have some confusion I'll gladly help to remove your confusion. I'll know if you studied because you'll start using the correct meanings for terms.

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#2

### Re: power consumption

04/29/2012 9:36 AM

Save us all a lot of work in the future.

Use the charts that abound on the web.

American Wire Gauge table and AWG Electrical Current Load Limits ...

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#3

### Re: power consumption

04/29/2012 1:08 PM

Proper conductor sizing is based on only 3 things: amperage, length, and LOCAL CODES. But here's a harsh reality: the fact that you had to ask this question immediately identifies you as someone unqualified to perform this most basic of electrical engineering tasks. Please turn this over to a qualified professional before you cause a fire. This forum, and all others like it, are not a substitute for proper engineering practices.

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#4

### Re: power consumption

04/29/2012 1:14 PM

Agreed!

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#5

### Re: Power Consumption

04/29/2012 3:26 PM

Single phase KVA = VA/1000.
Three phase KVA = VA√3/1000.
KW = 0.746 HP.
KW = KVA cosφ, where φ = phase angle between V and A; cosφ is also called power factor.

Wire sizing is primarily by amps, but also depends on voltage drop, ambient temperature, cable configuration, and local regulations. [Repeating JRaef.]

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#7

### Re: Power Consumption

04/30/2012 11:46 AM

Ok, OK,

Proper conductor sizing is based on only 3, no, 5 things: amperage, length (because of voltage drop), ambient temperature, cable configuration and LOCAL CODES. ...

Do I hear 6?

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#8

### Re: Power Consumption

04/30/2012 12:06 PM

Lets not forget insulation temperature range. Then again this is a little redundant. All of these attributes should be part of the local codes in the first place.

Then there are the wacky conductor sizing conditions that just aren't in any code book. 500 amperes of pulsed current into an ultra-high vacuum chamber that powers a superconducting kicker magnet for just one microsecond every ten minutes to four hours. Try to find that one in the NFPA 70.

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#9

### Re: Power Consumption

04/30/2012 5:57 PM

Article 210.68.A.1 "Wacky conditions"

"You are S.O.L, good luck with that..."

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#6

### Re: Power Consumption

04/30/2012 3:18 AM

British Standard 7671 should eliminate all confusion. If it doesn't, then consult a qualified electrician.

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#10

### Re: Power Consumption

05/01/2012 7:43 AM

hi guys,

Thanks for your interesting response. For a non qualified like me can you please tell how much amperes does the machine consumed if the nameplate indicates 10KVA, 400V.

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erlo (1); JRaef (3); lyn (2); PWSlack (1); redfred (2); Tornado (1)

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