240v to 480v downgrade - Page 2
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  1. #21
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    My take is, you have one of the earlier European, "world model" units that were built for high or low voltage, from the factory. Yours happens to be the 400V Y model. It has a variable frequency drive and motor that was built around the European voltage of 400/230V Y, but built with enough variance capability to go from 380 - 460V Y, able to run on most systems.

    The VFD is the thing that needs a Y supply system, most parts of the world have this type system as standard. However your RPC output is similar to a Center tapped delta, it has a wild leg, and the voltages are not symmetrical, with respect to ground. Most VFD's aren't approved to use on a center tapped or corner grounded delta. Due to the way that the system voltage suppression MOV's are configured.

    In a shop that has a 277/480V Y supply no problem, it's built with enough variance for that. Or the low voltage configured model 200-230V Y, can run fine on our 120/208Y systems. Center tapped delta and corner grounded delta's can stress the drive components.

    I have done several of similar type units over the years, by Kaiser, Sullair and Ingersoll Rand, they are all similar. On the ones that were in facilities with a center tapped delta supplies, we used a transformer to convert to a Y system, to avoid problems. But those type transformers are a little more rare in the used market, new is expensive, and usually a lead time.

    In your case you would need a 240V Delta input and a 277/480V Y output, that would be a standard setup. For a KVA size you would want 1.5X the load size to prevent excessive voltage drop when the unit is starting, especially in the case of a RPC supply.

    ir-400vy-12.5kw.jpg

    The motor tag list 28A @ 400V = 19.3KVA(28x400x1.73) The desired transformer size then would be 19.3KVA x 1.5 = 29.1KVA The next standard transformer size would be 30KVA.

    I took a look for a used unit on Ebay on your side of the US. Didn't find any ideal matches, that is 30KVA, 240V Delta Primary- 277/480Y Secondary. MGM transformer is from your coast and you may be able to find a decent price on a new unit out there.

    But I did find some usable ones, at a decent price. This one has four taps on the primary 230/240/460/480V delta and a secondary of 400/230Y which is the design voltage of your equipment. It also has adjustment taps on the output, which would allow some additional adjustment for your field conditions. And the price is reasonable.
    marelco-30kva-transformer-m-14799e-pri-v230240460480-delta-sec-v400wye.jpg

    Marelco 30KVA Transformer M-14799E Pri V:230/240/460/480 Delta, Sec V:400WYE/230 | eBay

    If you used a more common delta/delta 230V to 460V unit you then would need to corner ground it, to have a ground at all. And this is the worst possible configuration for a VFD input. If you do decide to go this route, make sure your electrician fully understands on how to properly bond the transformer secondary output, to ensure that the compressor has a functional ground.

    SAF Ω

  2. #22
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    Lets explore the EZ options first.

    Take a picture of the inside of the motor junction box.
    There should be 3 or 6 wires going to the inside of the motor.
    If 6 wires, and 3 of them are jumpered, you could reconnect for the lower voltage.

  3. #23
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    That solves the motor issue. What about the VSD that expects 380-460v?

    Sent from my HTC6545LVW using Tapatalk

  4. #24
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    Quote Originally Posted by claya View Post
    What about the VSD that expects 380-460v?
    You haven't shown us one in your photos yet!

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    VSD is in the schematics. The drive motor, solid state relays, etc are 380v-460v 3ph.

    Sent from my HTC6545LVW using Tapatalk

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    Normally a proprietary unit.
    ir15hpvsd_schematic-1.jpg

  7. #27
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    Quote Originally Posted by claya View Post
    VSD is in the schematics. The drive motor, solid state relays, etc are 380v-460v 3ph.
    It is NOT wise to make assumptions on what you do, or do not have in the electrical panel, based solely on the schematic.
    I don't see a VFD/VSD in any of your pictures, so either you have one (not on the schematic) that you haven't shown us yet, or you don't have one.

    "At 240V, it looks like the compressor wants about 20A FLA." BUT the motor is clearly marked "28A @ 400V" so at 240 Volts reality is more like 47 ~ 50 Amps per phase.

    Very carefully reread my warnings in post #17

    Bill


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