Calculating Amps On A Single Phase Regulator

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dsmith411

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We are using Three Single Phase Regulators / Platform mounted on a Three Phase Line.12470/7200. The regulators are 333kva. How is the best way to figure how many amps each Regulator is good for ?
 
KVA RATING ..... AMPERE RATING*
38 ...................50/56
76.2 ................100/112
114.3 ...............50/168
167 .................219/245
250 ................ 328/367
333 .................438/490

*The first value is the 55C rating.
The value to the right of the slash
is the ampere rating at 65C.

Amp Rating with reduced % regulation

% Reg .... (Amps % OF 55C Rating)
+/- 10 ......... 100
+/- 8.75 ...... 110
+/- 7.5 ........120
+/- 5 .......... 135

You can increase the ampere rating of the regulator if you are able to reduce the % regulation. This depends on where you install the regulators in the distribution line. Why are you installing the regulators? Has anyone done a load study to determine the actual load?
 
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Add Amp

Add Amp

Above post is correct, to be really sure, always refer to manufacturer spec. However, I assume the regulator is ?10%, that is ?720V nominal. The regulator can add or subtract up to 720V to the 7200V line. If the thermal rating is 333kVA, the nominal full-boost/buck current will be 333,000VA/720V = 462A.

May regulators have up to 160% increase in amperage if operation is below ?5%. HOWEVER: some large regulators are limited by the bushing current rating NOT the kVA.
 
Amps On A Three Phase Regulator

Amps On A Three Phase Regulator

The reason we are setting regulators is that there is no regulation on the 13kv bus that the feeder breaker is on.The load we will have on this line figures to be a little over 300 Amps. I would like to see a formula on converting the kva rating on the regulator as to how many amps that is equal to or that it will carry at 7200v.
 
Amps On A Three Phase Regulator

Amps On A Three Phase Regulator

Sorry about the last part of my last reply. I overlooked the formula where they had 333,000/720 =462A. I thought maybe that you would have to divide by 7200v.
 
Regulators unlike Transformers

Regulators unlike Transformers

Voltage regulators are rated as the maximum voltage across the regulator (in-out) times the current through the regulator. Since a 10% regulator on a 7200V (line-ground) system raises/lowers the voltage by 720V, that is the voltage used.

One thing I find odd is that if this was a fixed ratio autotransformer, the rating (kVA) would be based on the through-put, so its rating would be amps times 7200V. But, because this has adjustable taps, it is different. Just traditional practice but a possible "gotcha."
 
Calculating amps on a single phase regulator

Calculating amps on a single phase regulator

Thanks a lot for the answer. You have explained it very well and answered my question on why the 7200 doesn't play a part in the formula.
 
beanland said:
But, because this has adjustable taps, it is different. Just traditional practice but a possible "gotcha."
Click to expand...
From the practical, "how is it built" point of view is this because the total heating in the secondary will go down with the number of turns, so more total current can be supplied when using fewer turns? Or that the winding wire for the lower taps is larger? Or just that the available power is really set by the power capability of the primary?
 
Look at References

Look at References

Cooper Power published a document titled "How Step-Voltage Regulators Operate" in 1993. That might help.

If not available, try to get Cooper document S225-10-10 which is service information on VR-32 regulators. It has a slew of schematics.
 
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