How to you determine the impedance of a line reactor placed on the line side of a VFD ?

[bdn2004]

Attached in a manufacturer's drawing of a line reactor that is found on the supply fan of an HVAC unit at a plant where we are doing an arc flash evaluation.
I'd like to show this in series with the VFD. T

The program we are using has these parameters to fill in for a reactor:
1) Ampacity (225, 600, 1000,....6000)
2) Impedance kVA (3-phase)

and then it calculates the ohms from these numbers. btw this is a 480v, 3 phase, 50Hp motor. This line reactor says it's 65A on the nameplate.
The manufacturer told me this unit is 295 microhenries impedance.

I tried this: (480V)(65A)(1.732) = 54kVA. The program says the impedance in ohms from that is X1 = 0.018 , X0 = 0.018 and X/R is 18.9812
I'm not seeing 295 microhenries. Where am I screwing up?

 

[ScottyUK]

Work out the ohmic reactance from j[ω]L - assuming this is a 60Hz system it is 0.111[Ω]/phase.

If you want kVA the multiply the above impedance by the line current: 7.22kVA per phase, or 21.7kVA total.

 

[bdn2004]

ok so you're saying....

jwl = (2*pi*f)*L = 2*3.1472*60*.000295 = .111 ohms/ph
I do want kVA ... but I * Z = Voltage, not kVA. Am I missing something?

 

[jghrist]

If you want kVA the multiply the above impedance by the line current: 7.22kVA per phase, or 21.7kVA total.

I think you mean multiply by the current squared to get 470 VA per phase or 1.41 kVA total.

 

[Parchie]

I do want kVA ... but I * Z = Voltage, not kVA. Am I missing something?

Your line reactor is roughly 3 %Z. Divide the ohmic value of your reactor by the ohmic equivalent of your motor load which is about 4.08 ohms per phase (@ a PF of 0.72).
%Z of reactor = 0.111/4.08 = 0.0273 or ~ 3%!

 

[bdn2004]

Ok I called the maker of the software and asked them how to do it. We're close. Attached is a white paper they sent me.

 

[bdn2004]

2*pi*60*.295 = 111 ohms ?

I'm not getting what is to go in these boxes....Ampacity and kVA are the only two parameters.
What you're saying is the value should come out. Z = .03. ok but how to get that into the program based only on kVA and ampacity?

 

[Parchie]

295 micro-henries = 0.000295, not 0.295

 

[davidbeach]

microhenries, not microohms.

[edit]And the previous post was edited/corrected while I was typing. [/edit]

 

[ScottyUK]

jghrist,

Yes. It was late here!

Thanks.

 

[bdn2004]

Just as a follow up on this, the correct answer is .111 ohms and 1.41 kVA. It was user error on my part. How was I to know the default picks in the program could be overridden? Now I know. Thanks ScottyUK and jghrist.