Chinese scroll air compressor
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    Default Chinese scroll air compressor

    Looking at Alibaba for scroll air compressors for my new shop.
    7.5hp 380/3/50

    I have been looking for information on vfd's and transformers.

    Trying to do this on cheap side.

    How do I get from 220vac/single phase/60hz to: 380vac/three phase/50hz?

    What I have read says I can step up from 220vac to 440vac with a transformer. Then use a vfd to set hz and phase. I don't know if that will work and don't understand how it all works together.

    Any insight is helpful.

    Thank you,
    mtadamek

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    Why on earth would you buy a compressor from China with a 380V 50Hz motor on it? Cheap aint so cheap when it fails...

    But yes, if you step up your 240V 1 phase to 480V 1 phase, then feed a 480V VFD that is capable of running from 1 phase input and sized at twice the motor amp rating, you can program the VFD to put out 380V 50Hz. That's a lot of trouble to be able to use a cheap piece of Chinese junk though. I would just buy a cheap chinese compressor from a local store that comes with a 230V single phase motor.

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    Default Chinese compressor

    We were looking at a couple Chinese/U.S. screw compressors also. The vendors we looked at had 60hz. I would really have to do some digging to find the vendors. We ultimately found a used 15hp I-R, so did not pursue it anymore. One of them was Blue...

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    Default Scroll

    Quote Originally Posted by Jraef View Post
    Why on earth would you buy a compressor from China with a 380V 50Hz motor on it? Cheap aint so cheap when it fails...

    But yes, if you step up your 240V 1 phase to 480V 1 phase, then feed a 480V VFD that is capable of running from 1 phase input and sized at twice the motor amp rating, you can program the VFD to put out 380V 50Hz. That's a lot of trouble to be able to use a cheap piece of Chinese junk though. I would just buy a cheap chinese compressor from a local store that comes with a 230V single phase motor.
    Going down a rabbit hole on air compressors. They have some really nice scroll machines with air dryer and tank built in. Very nice and very reasonable. Problem is that voltage. I did find out 220v/3/60 is an option. It is more expensive but the work around with a vfd seems to be much better option. I dont see any issues with doing that.....thoughts?

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    Quote Originally Posted by mtadamek View Post
    Looking at Alibaba for scroll air compressors for my new shop.
    7.5hp 380/3/50 I have been looking for information on vfd's and transformers.
    Trying to do this on cheap side.
    It won't take long for the 'cheap route' to become 'very expensive'...

    A better investment, is to find a used industrial-grade unit, and give it a thorough cleaning, inspection, and put it back in 'gentler' non-industrial service.

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    Quote Originally Posted by mtadamek View Post
    I did find out 220v/3/60 is an option. It is more expensive but the work around with a vfd seems to be much better option. I dont see any issues with doing that.....thoughts?
    For export you can get 60 hz 220v for sure. However, 380v 50 hz is electrically the same as 440v 60 hz. Should be able to just run it on 440 but I do not know about the voltages for switches and contactors and such. VFD would be a bad idea, imo.

    We had a Guangdong-built Sullair screw-type, maybe 15 or 20 hp, it worked great and not a blink in the two years I took care of it. New, though, you should expect that. I think it was about half the price they sell for in the US ? Probably the same compressor.

    Not sure I'd buy any of the cheapies though. I don't see the point in it when you can get a reasonable used brand name for the same money.

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    Quote Originally Posted by mtadamek View Post
    Going down a rabbit hole on air compressors. They have some really nice scroll machines with air dryer and tank built in. Very nice and very reasonable. Problem is that voltage. I did find out 220v/3/60 is an option. It is more expensive but the work around with a vfd seems to be much better option. I dont see any issues with doing that.....thoughts?
    Cheap VFDs don't tend to last long or work well. Expect lots of electrical interference, annoying motor whine, and errors relating to the pressure switch disconnecting the load.

    Also, transformers cost money in wasted energy.

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    At 7.5 hp just go with a good old piston type...Phil


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