Air compressor power supply — 200VAC, 400Hz

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Re: Air compressor power supply — 200VAC, 400Hz

Postby Jerry Biehler » Sat Jul 15, 2017 6:45 pm

Dang, 7-8 amps. So you are going to need a 3HP vfd which just dont come in 120v input.

I recommend something like this: https://www.driveswarehouse.com/wj200-022lf-2533

I have installed a LOT of VFDs, FWIW.

Its getting to be a decent amount of money spent on this thing, you might want to find someone that has 208 3 phase and hook it up to that first, it will run at proportionally lower speed but at least you will know it works before dumping money into a VFD you cant return.
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Re: Air compressor power supply — 200VAC, 400Hz

Postby ian_krase » Sat Jul 15, 2017 8:32 pm

At this rate it's sounding like it's not impossible that you might want a change of motors. Though of course the power requirements are not going away.
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Re: Air compressor power supply — 200VAC, 400Hz

Postby Rich Feldman » Sun Jul 16, 2017 12:08 am

>> you might want a change of motors.

From the voltage and current, the motor behind Sarvesh's nameplate picture is around 2.5 horsepower. (could work it out from the RPM and torque values). A 60 Hz motor of similar power would be much bigger, and not turn anywhere close to 12000 RPM.

Here's a contemporary motor made for 400 Hz 200 V 3-phase. 4.5 horsepower continuous duty, length 8.8 inches, weight 14 lbs.
me421asc.jpg
me421asc.jpg (14.45 KiB) Viewed 107 times
from http://www.400hertz.net/Products/ME-421SC.htm. Nice FAQ at http://400hertz.net/faqs.htm#1

I like Jerry's idea of firing up the unit on 60 Hz 208 V 3-phase. The compressor's flow would be reduced by a ratio similar to the power frequency ratio, but I will guess that its max pressure won't take a huge hit. The office cubicle wiring at my day job is based on 208 V 3-phase; each 120 V receptacle is connected to one phase and neutral.
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Re: Air compressor power supply — 200VAC, 400Hz

Postby Sarvesh Sadana » Sun Jul 16, 2017 4:14 am

You're right Ian, according to the pictures, they seem to require an RJ12 connector.

I don't think it would be very possible to change the motor. It is currently at the heart of the machine and it would be almost impossible to remove, not to mention the fact that a compatible motor would be very difficult to find.

Here are more pictures of the machine, as you requested. (For some reason, they are sideways. Click on it and it appears normally)

IMG_1200.JPG
The motor. As you can see, it is too deep inside to be easily removed.

IMG_1203.JPG
The compressor itself

IMG_1090(1).JPG
The operating instructions

IMG_1100.JPG
According to this, there is a secondary DC circuit. I believe it runs on 27.5 volt DC at 4 amps and purges the oil.


I can try to hook it up to a 60hz 208v socket, but I still don't have the connector required to do so. Would something like https://www.digikey.com/product-detail/ ... ND/2449325 work? (http://www.mouser.com/ProductDetail/Amp ... JWxw%3D%3D has the same part number and is cheaper, but for some reason the picture is different.)

Also, I found the same model (WJ200-022LF) used on ebay with 30 day return and a warranty for cheaper. http://www.ebay.com/itm/HITACHI-WJ200-0 ... SwrfVZSUhs

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Re: Air compressor power supply — 200VAC, 400Hz

Postby John Myers » Sun Jul 16, 2017 4:49 am

The pictures for both digi-key a Mouser sometimes don't match the actually part number exactly (which they warn you about somewhere), the pictures just give you a general idea of what it looks like.

You could just re-terminate the cable with a non Mil spec and less expensive connector.
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Re: Air compressor power supply — 200VAC, 400Hz

Postby Rich Feldman » Sun Jul 16, 2017 5:47 am

That particular VFD model (WJ200-022LF), according to the ebay listing as well as Jerry's link (driveswarehouse), needs 3-phase AC input. So you could use it as a frequency converter but not a phase converter. Jerry's experience, or maybe the product user's guide (linked at DW) might describe qualified exceptions to that.

You can't turn house power (single phase) into three-phase with just transformers.

John suggested cutting the plug off and substituting a less expensive connector. If you want to sort of follow a standard, the three-phase five-wire path seems to lead to NEMA L21 types.
170px-L21-30_plug_and_receptacle.jpg
170px-L21-30_plug_and_receptacle.jpg (5.1 KiB) Viewed 96 times
No straight blade/pin, only twist-and-lock variants. See also http://www.stayonline.com/nema-l21-20-l ... cords.aspx. On Monday I can see which kind are used in our labs, and on our Bridgeport. I have no idea what NEMA says about 400 Hz. That 400hertz.com company sells 200 V electric tools (with neither brushes nor semiconductors) and support equipment for jobs like concrete sawing. How about if you find out what connector convention they follow?

If the compressor and its weird plug with five round pins were mine, I would put single pin receptacle contacts on five insulated wires of appropriate thickness. Each would be individually insulated with heat-shrink tubing, maybe even 2 layers, then mated to the corresponding pin of the compressor plug. Finished off with some kind of strain relief, like splinting the connection with a broomstick and some duct tape.
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Re: Air compressor power supply — 200VAC, 400Hz

Postby Jerry Biehler » Sun Jul 16, 2017 9:47 am

The VFD will run just fine on single phase. They dont care, its not until you get to the big VFDs that they start looking for phase loss.

Yes, those connectors look like the mates to what you have on the pump.

You dont want to change the motor, it is not going to be a standard frame mount and is probably splined. It would be a nightmare.

Running the motor on 60 just means it will pump slower, it will still reach the same pressure since the frequency is what determines the motor speed.

You really need to pop open the control box and see what is going on in there before you do anything. I am guessing it uses the 28v in for the control circuit and any overpressure kickoff.
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Re: Air compressor power supply — 200VAC, 400Hz

Postby Sarvesh Sadana » Sun Jul 16, 2017 10:43 am

Even though it can run on single phase power, would it not be preferable to use one designed for it, such as https://www.driveswarehouse.com/nes1-022sb-2692 or https://www.driveswarehouse.com/ode-3-2 ... r-invertek?

I think I will simply try to follow the wiring diagram on the VFD I purchase rather than try my hand at connecting it to a different plug. I will still need a transformer to get it to the 200 volt input power.

I'll also try to find any more information on the accessory DC circuit. I'm hoping it's not crucial to the operation of the compressor. I do have a lab supply that I can use for it, though.

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Re: Air compressor power supply — 200VAC, 400Hz

Postby Rich Feldman » Sun Jul 16, 2017 4:29 pm

I think John and I were referring to the 400 Hz connector, not the connector between VFD and the wall. Parametric search tools on distributor websites just taught me a lot about "18-11" or "18, 11" MIL/Aero circular connectors. Stumbled upon one good deal at Allied Electronics, and it even has a picture with correct number of pins. :-)
round_one.PNG
Even when not "on sale", it looks like this sort of connector is in the same price ballpark as NEMA plugs and sockets when you get into three-phase.

Re. single phase input to VFD, I knew it generally works, and the connection drawing often says which two of the three terminals to use. So it was a surprise to see "three phase only" in the product description. Jerry, and/or the product documentation, can explain how to compute the two-wire input current and derate the output current if necessary. (I'm thinking about ripple current in bus capacitors, PFC circuit operation, etc.)
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Re: Air compressor power supply — 200VAC, 400Hz

Postby Jerry Biehler » Tue Jul 18, 2017 5:39 am

Modern VFDs do not need to be derated, old ones did but new ones just dont care, at least at this size of VFD. When you get to 10HP plus then you might start worrying about derating. Worst case scenarios is you get a under voltage alarm on the buss, but with running the motor at 200v that will be just about impossible.

Really, you can get just about any 3 hp 240v rated VFD and run with it, I would just not buy anything chinese. Oh, and make sure it actually does 400hz, some drives top out at 360.

I use mitsubishi servos on my cnc mill and lathe and they are intended for three phase and I have never had an issue, and the spindle motor on my lathe is a 5kw servo. The servo drives are basically a VFD but 3 times more complicated.

You REALLY need to open the control box and see whats going on, my guess is it wont work without aux DC.
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