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I=kw*1000/E*1.732 primary side 90.3 amp. Secondary side 208 amp. 100 amp 277-480 breaker good for primary side usually i install 200 amp 208-110 secondary side. Primary wire size #2 secondary side 3/0

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11y ago
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11y ago

Primary current for a 225kVA transformer at 480V is 270.6 amps full load. NEC code says you can size the primary protection device by 125% if there is no secondary protection. 270.6A * 1.25% = 338.25A. Since this is a non-standard rating of a fuse or non-adjustable circuit breaker, a higher rating that does not exceed the next higher standard rating shall be permitted. (NEC2011 Table 450.3(B) Note 1.)

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5y ago

Assuming 3 phase secondary, maximum secondary current would be 216 Amps. The wire should be suitable enough to cater to 216 amps plus 10% over load factor. You need to choose aluminum or copper and factors like air, or ground, in trey, bunched or single. Better to refer to a chart provided by any reputed cable manufacturer.

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13y ago

#6 wire

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Q: What size wire should you use to feed a 75 KVA transformer 480 3 phase primary - 208 volt 3 phase secondary?
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Is possible to put 3 phase transformer primary as secondary and secondary as primary?

A: The only way can be possible if the transformer is an isolation type. Yes, you can put the input into the secondary side. This will create a step-up transformer.


How you differentiate between single phase and three phase transformer?

A single-phase transformer works with a single-phase supply, while a 3-phase transformer is used with a 3-phase supply. A single-phase transformer has 2 wires on the primary and secondary (ignoring taps) while a 3-phase tansformer has 3 or 4 wires on the primary and secondary.


How many amp in 480 vac 3- phase primary transformer if the secondary it's 120 vac?

This 480-v three-phase transformer probably has a 208-v three-phase secondary which has 120 v from each line to neutral. In that case the primary current is 0.433 times as much as the secondary current, so 100 amps in the secondary means 43.3 amps in the primary.


How should I calculate this. A single phase transformer is rated at 99kVA The primary voltage is 6.6kV and the secondary voltage is 220V Assume no losses and calculate The full load primary current?

First find the ratio of the transformer. 6600/220 volts. Second find the secondary current, I = W/E, 99000/220. Third divide the secondary current by the transformer ratio. The answer will be the primary current. To check your answer (W (or VA) = V x A) multiply the primary current times the primary voltage and the secondary current times the secondary voltage and they should both equal the transformer's kVA.


What is the relationship of primary windings of a transformer to the secondary windings regarding output and input voltage?

The phase relationship between the primary voltage and the secondary voltage of a transformer is 180 degrees (typically) on single phase transformers. If working with three phase transformers, a zero phase shift is often used in Y/Y grounded transformers. If the transformer is wired Delta / Wye, the phase shift will be 30 degrees. I've seen transformers with a phase shift of 150 as well (quite abnormal, but it exists!) due to the starring and a delta / wye configuration. If you are looking at a transformer phasor diagram, this will show the phase shift between primary or secondary (three phase transformers). For single phase, there should be a drawing showing polarity markings - what goes in the polarity marking on the primary comes out on the secondary polarity marking.

Related questions

Is possible to put 3 phase transformer primary as secondary and secondary as primary?

A: The only way can be possible if the transformer is an isolation type. Yes, you can put the input into the secondary side. This will create a step-up transformer.


What is the voltage phase shift between primary and secondary line voltages in star-delta transformer connection?

The voltage phase shift between primary and secondary connections in a transformer is 180 electrical degrees.


What is the three phase transformer?

it has three primary windings & three secondary windings.


Does the formula used to calculate the turns ratio uses the phase voltages and phase current?

For a transformer, the turns ratio always applies between its primary and secondary windings. So the turns ratio for a three-phase transformer is the ratio of primary to secondary phase voltages, not between line voltages.


How you differentiate between single phase and three phase transformer?

A single-phase transformer works with a single-phase supply, while a 3-phase transformer is used with a 3-phase supply. A single-phase transformer has 2 wires on the primary and secondary (ignoring taps) while a 3-phase tansformer has 3 or 4 wires on the primary and secondary.


Why phase displacement is maintained between primary and secondary windings of the transformer?

To eliminate certain harmonics.


How many amp in 480 vac 3- phase primary transformer if the secondary it's 120 vac?

This 480-v three-phase transformer probably has a 208-v three-phase secondary which has 120 v from each line to neutral. In that case the primary current is 0.433 times as much as the secondary current, so 100 amps in the secondary means 43.3 amps in the primary.


How should I calculate this. A single phase transformer is rated at 99kVA The primary voltage is 6.6kV and the secondary voltage is 220V Assume no losses and calculate The full load primary current?

First find the ratio of the transformer. 6600/220 volts. Second find the secondary current, I = W/E, 99000/220. Third divide the secondary current by the transformer ratio. The answer will be the primary current. To check your answer (W (or VA) = V x A) multiply the primary current times the primary voltage and the secondary current times the secondary voltage and they should both equal the transformer's kVA.


Is 3 phase star transformer has more winding than delta?

The # of windings in a transformer are based on the primary and secondary voltages the transformer is rated for not the way the windings are connected.


What is the relationship of primary windings of a transformer to the secondary windings regarding output and input voltage?

The phase relationship between the primary voltage and the secondary voltage of a transformer is 180 degrees (typically) on single phase transformers. If working with three phase transformers, a zero phase shift is often used in Y/Y grounded transformers. If the transformer is wired Delta / Wye, the phase shift will be 30 degrees. I've seen transformers with a phase shift of 150 as well (quite abnormal, but it exists!) due to the starring and a delta / wye configuration. If you are looking at a transformer phasor diagram, this will show the phase shift between primary or secondary (three phase transformers). For single phase, there should be a drawing showing polarity markings - what goes in the polarity marking on the primary comes out on the secondary polarity marking.


What is the mutual coupling in single phase transformer?

primary winding flux links with secondary winding produses voltage across the secondary winding


Transformer 208 volt primary and 480 volt secondary three phase 75 kva what size fuses on primar and secondary?

200 and 100