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  1. #1
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    Question Single Phase to 3 Phase

    I have owned a Hitachi Scroll compressor since 2013 that was originally hooked up to 3-phase 208 at my old lab.
    Currently I am moving the unit to a new location where 3 Phase is not supplied nor is it affordable to have run.

    So I need a way to convert single phase over to 3-phase power.

    What is a cost effective and quiet way of doing this? (I can build an enclosure if I absolutely have to...)
    Can you please provide a link to a specific unit that would work? I need something that will last a long time.
    This compressor runs for 5 minutes and rests for 10-15 min then runs for 5 min when in use. It is setup with a 250 Gallon receiver tank.

    I have your standard 110 and 240 single phase outlets at the new location.
    This unit requires 208 or 230 3-Phase at 60Hz to operate.

    So I need something that will convert single phase 240V to 3 Phase 208 or 230 (208 preferred as that is what the unit was on)
    The quieter and more affordable the better.



    UNIT SPECS
    Hitachi Scroll oilless air compressor, power
    230/3/60, air cooled, 120psig, rated for 21.2 CFM
    Model SRL-5.5M6L


    FULL MANUAL OF UNIT (Link)
    https://service.relevantsolutions.co...e%20060109.pdf

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    A VFD should satisfy your requirements. Although they dropped in price, the new ones of this power range are not very cheap. But there are plenty of used ones to buy.

    You can buy a widely available 230v/3-phase-to-230v/3-phase VFD. It will be able to convert single into 3-phase too, but you'll need to derate it. So for your 7.5HP compressor get a 15HP VFD (there is a chance 10HP may work too, but I'd play it safe).

    This derating is needed when you use a VFD not speciafically designed for a single-phase input. Just check that the VFD's phase loss detection feature can be deactivated.

    Otherwise, just buy a 7.5HP VFD speciafically designed and rated for sigle-to-3-phase conversion. But they're harder to find used and, usually, more expensive.

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    Where can I find a unit like this? I was unable to locate one of this size on Grainger.

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    You can place a WTB ad on this forum, check e-Bay or other equipment auctions. And if you need a new one, you can check vfds.com or many other Websites (incl. Grainger).

    Since it's not going to be an inexpensive purchase, I'd stronly suggest you to think it over. If the compressor is not going to be the only 3-ph machine of yours, think about something else rather than VDF: something that will be able to feed all your machines (vs. VFD that normally serves one machine only and requires machine rewiring: there should be no switches between VFD and the motor, control circuits should be managed correctly, etc.). An RPC can be a good alternative: all shop can be fed by one RPC, no rewiring of the machinery needed, if low-speed idler motor is used, RPC can be low-noise. Unless you need some special features such as electronic variable motor speed control, soft start and quick break, you don't really need VFDs.

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    [QUOTE=TheMetrologist;3477648]I have owned a Hitachi Scroll compressor since 2013 that was originally hooked up to 3-phase 208 at my old lab.
    Currently I am moving the unit to a new location where 3 Phase is not supplied nor is it affordable to have run.

    If you anticipate additional three phase items in the new location, and if money is not a big object, then a Phase Perfect installation might
    be a good approach. A box you mount on the wall, connect to single phase power, and then run the output from this around your lab
    to wherever you will need the three phase power. It's basically a turn key solution.

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    [QUOTE=jim rozen;3477835]
    Quote Originally Posted by TheMetrologist View Post
    I have owned a Hitachi Scroll compressor since 2013 that was originally hooked up to 3-phase 208 at my old lab.
    Currently I am moving the unit to a new location where 3 Phase is not supplied nor is it affordable to have run.

    If you anticipate additional three phase items in the new location, and if money is not a big object, then a Phase Perfect installation might
    be a good approach. A box you mount on the wall, connect to single phase power, and then run the output from this around your lab
    to wherever you will need the three phase power. It's basically a turn key solution.

    I looked at Phase Perfect and I don't see an option to go from 240V Single to 208 or 230 3-Phase.
    I could only find a unit that would go from single phase 240V to 3 Phase 240V.

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    Thank you for this, I have about 3 days to make a decision. The CMM I am running requires a minimum of 6CFM to operate and the machine is now up and running with a temp compressor.
    I don't believe a VFD would work for me as the wiring of this Hitachi unit is very complex and I need something more plug and play.

    Essentially I need a quiet device that will make the conversion from 240V single to 208 or 230 3phase and be as quiet as possible.
    What brands of RPC's are reputable and have strong support and warranties?

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    The voltage spec. usually has a range, you could check with Hitachi for this particular model. A standard VFD would not be a plug and play option in this application. You might look at a PhasePerfect PT010 if you only need to supply just the compressor, otherwise a larger model if you have a 3 phase refrigerated drier, etc.. If you need to drop the voltage to the compressor you could use a 5% Line reactor, or a transformer on the input side of the PhasePerfect. The phasePerfect output voltage is essentially = to its input voltage.

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    [QUOTE=TheMetrologist;3477854]
    Quote Originally Posted by jim rozen View Post
    I looked at Phase Perfect and I don't see an option to go from 240V Single to 208 or 230 3-Phase.
    I could only find a unit that would go from single phase 240V to 3 Phase 240V.
    Look closely at the manual for the scroll pump. The input voltage will have a tolerance range.

    I doubt it is running on 220, or 230 volt three phase right now. Most industrial locations supply
    240 volts these days. As mentioned you can buy two buck transformers to bring the voltage down
    somewhat. No moving parts, less than a few hundred dollars.

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    WNY Supply

    Those are well built RPCs. But if you want a really low-noise one, get a 1200 rpm motor. The faster the motor, the noisier it will be. And I mean MUCH noisier. I absolutely couldn't stand a brand new 6500rpm Baldor, whereas my heavy monster is VERY quiet. Nevertheless, it's always a good idea to put the RPC idler away from your shop space or make a vented enclosue.

    I bought my 15HP motor used from a local motor repair shop. My panel was purchased from WNY. If you buy your own motor, make sure WNY knows what motor you have to adjust the panel accordingly.

    Running a compressor or other pre-loaded machinery requires you to get an RPC rated higher than the load (1.5-2 times higher). For you it'll be 10-15HP.
    Last edited by MichaelP; 01-21-2020 at 08:33 PM.

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    That's a fast motor for a rotary....


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  14. #12
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    Thanks Jim, the typo has been corrected.


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