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  2. Calculating Amperage for stepdown transformer | Information by...

    forums.mikeholt.com/threads/calculating-amperage-for-stepdown-transformer.123904

    I am conducting a photovolatic design in which I need to use a step down transformer going from 480V to 240V. I understand that my amperage will roughly double, but how do I calculate exactly what my amperage will be after the step down? I need this in order to correctly size my wires at my inter-connection point so that they may handle the ...

  3. REVERSING A TRANSFORMER FOR STEP-UP | Information by Electrical...

    forums.mikeholt.com/threads/reversing-a-transformer-for-step-up.51

    Re: REVERSING A TRANSFORMER FOR STEP-UP "2. Magnetizing inductance is proportional to the square of the number of primary turns. If we have a step-down of 20:1 say, then the magnetizing inductance seen in a backfed transformer is 1/400 instead of 1/20 as we might expect.

  4. 277/480V 200A supply stepped down to 120/240V...

    forums.mikeholt.com/threads/277-480v-200a-supply-stepped-down-to-120-240v.111869

    However, I suspect this does not have anything to do with the OP question - which I am guessing is about transformer physics. On that note: Yes, following kwired's statements, considering a 480/240D transformer, 200A in will give you 400A out. And 200A of 480v, 3ph, is 166kva. Reliably feeding it from a 480V, 200A service is a diferent question ...

  5. 480 volt step down transformer question | Information by...

    forums.mikeholt.com/threads/480-volt-step-down-transformer-question.145806

    The POCO will set a 480 volt single phase trans. at a minimal cost I would then step down the voltage at the load to 120/240 volts. Here is what I am proposing to do after doing the voltage drop calculations. Use AL 500kcmil with 350 neutral with a 25KVA step down transformer at the load.

  6. How to size a 480 to 240/120V Transformer - Mike Holt's Forum

    forums.mikeholt.com/threads/how-to-size-a-480-to-240-120v-transformer.124181

    Transformer basics just says if you have a 15kVA transformer that primary fully loaded to 15kVA will be 31.25 amps and secondary would be 62.5 amps. There are some losses in the transformer and primary actually would draw slightly more but this is generally disregarded.

  7. 277/480 Step dowm 120/208 425 feet | Information by Electrical...

    forums.mikeholt.com/threads/277-480-step-dowm-120-208-425-feet.138348

    Hey all Thanks in advance I have to re-feed a store and run new conduit over the roof . I have to run approx 425 feet to re-feed an existing transformer. 277/480 Step down transformer to feed to and 150 amp 120/208 panel all 3 phase There is and existing transformer and 120/208 panel I...

  8. Voltage Drop Calculation Through Transformer | Information by ...

    forums.mikeholt.com/threads/voltage-drop-calculation-through-transformer.2570065

    I need to make sure that my 480v distribution system which could be made up distribution to many locations brings me to an appropriate voltage drop to the primary of my 480-208/120V step down transformer and then confirm that the voltage drop across the transformer and the route all the way to the 208V (or 120V) utilization equipment is within ...

  9. Generators with step up/down transformers. | Information by...

    forums.mikeholt.com/threads/generators-with-step-up-down-transformers.89428

    Maybe a better example is a 480V generator feeding a 208/120V transfer switch through a transformer. The generator output breaker provides overcurrent protection for the cables and transformer and another breaker at the transformer protects the 208V cables to the ATS. During normal operation both breakers are closed and the generator off.

  10. Voltage Drop Before and After a transformer | Information by...

    forums.mikeholt.com/threads/voltage-drop-before-and-after-a-transformer.88541

    The transformer's internal impedance is also important. However, the unloaded secondary voltage of a tightly coupled ferromagnetic transformer may be closely related to the turns ratio. I measured an unlabeled, I do not know where the cover is, transformer, about 0.5 KVA, and measured the input and out voltage with no load.

  11. Sizing Circuit Breakers for Transformer - Mike Holt's Forum

    forums.mikeholt.com/threads/sizing-circuit-breakers-for-transformer.86930

    Can you guys confirm if I sized transformer, primary and secondary circuit breakers correct? Primary Voltage: 480 volts, 3 Phase Primary Load: 231.97KVA (279.1 Amps) Secondary Voltage: 120/208 volts, 3 phase Seconard Load: (644.36 Amps) I selected a standard 225KVA transformer. Primary MCB: 350 Amps Secondard MCB: 800 Amps