stepdown with tapping

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thekingtut

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cairo,egypt
i am a designer of a project in KSA the supply voltage is 380v 3ph there are some panelboards in the project required 220 3ph/1271phv so i will have a transformer to stepdown but the distance to farest outlet 127v will be 100m my question is . can i have a transformer dry type that have something like tapping to have secondary voltage of 127v and the total voltage drop not exeding 5% total ,please tell me about its manufacture name.
thanks alot
 
You best bet would be to contact a manufacture directly, they will custom wind (for a price) or you could purchase a 480 to 208/120 adjust taps to provide lowest secondary voltage and use buck boost transformers to lower the voltage to the prescribed levels. Lastly you could use two transformers, with lowest taps then stepping back up using correct taps to achieve what you require.
 
If you overtap the voltage to negate the voltage drop over 100m, the loads close to the tranformer not affected by the voltage drop will run hot. If you end up with devices near the over tapped xfmr that are rated for 120V use ("american" voltage) as opposed to 127V ("european" voltage), there is a possibility that they will exceed their listed voltage (generally +/- 10%ish).

You may want to consider a 2nd xfmr nearer to the loads and upsize the primary feeder to cover the voltage drop. If there are only a couple of circuits at that long distance it may be cheaper to upsize the brach circuit wire to cover the voltage drop.
 
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