Adapter for 550 ac 3 phase motor

There are phase converters which derive three phase from single phase. There are UPS which offer three phase output from single phase input I believe. There might be a much better solution out there. I'm not real familiar. If you post the ratings of your 3 phase motor (and your single phase supply) that might help people give you answers.

j

Adaptor?????

There are several manufactures of single phase to 3 phase with in the voltage range. They do it with capacitors. As for more than doubling the voltage, not familiar with anything that will do that.

550 v is not something I am familiar with. What is the operating frequency?

The biggest motor I wamt to run is a 3HP

550 Volt would be an old utilization voltage for a 600 V nominal distribution system - but more recent practice would have the motor nameplate say 575 V. 600 V 3 Phase 60 Hz is a common industrial distribution scheme in many places in Canada and a few parts of the US. 600V systems are nice because it's very nearly 1 amp per horsepower, per kVA or per KW.

Bill

I guess 550V is to 600V as 110V is to 120V. That is, when "they" decided the nominal voltage at a wall outlet should be 120V rather than 110V (when was this, the 50s?), nominal 550V (5 times as much) became 600V. (Even today so many people describe something like an electric dryer as using "two twenty")

I know 550V was once used in the turn-of-the-century "mill" buildings in Massachusetts as an electrician neighbor has mentioned it and I've seen marked 550V knob-and-tube(!) wiring still in use in the 90s. I don't know if 600V is used here or if everything is 480V now.

I think what happened is the rules for voltage drop tightened up, too, so that the 550 V utilization/600 V nominal system that allowed for an

8% voltage drop became a 575/600 system with 4% allowed drop. A 480 V distribution system I think would have had 440 V utilization in the "old days" and 460V today. In old areas of a mini-mill I used to work at, built up to 1953 or so, many panelboards were marked "550" (though they probably should have been marked "600" for use with "550" motors).

Knob-and-tube, if properly installed and maintained, is still reasonably safe, though since the newest knob-and-tube installation you're likely to run across is going to be 50 years old, it's very likely that it's been abused or at least overloaded. Old insulation does get dry and brittle, but I don't think people who installed knob-and-tube relied on the cable covering as the only insulation.

I visited a paper mill at International Falls MN which had the interesting property that some buildings had 600 V systems and some had

480 V systems, which I'm sure caused trouble in the spare parts stock over the years, e.g., the last remaining C-flange 600 RPM motor on the shelf was 575 V but the one that just burnt out was a 460 V, etc.; anyone who's worked in electrical maintenance in an industrial plant will want to see only *one* 3-phase system voltage.

Getting back to the original topic, a phase converter for a 3 HP motor is going to cost at least as much as buying a new 220 V single-phase motor; for just one motor, it may be more ecnomical to change the motor. The rec.metalworking group has this sort of thing in their FAQ since hobby or small machine shops are constantly picking up good deals on 3-phase machine tools.

Bill

| I guess 550V is to 600V as 110V is to 120V. That is, when "they" decided | the nominal voltage at a wall outlet should be 120V rather than 110V | (when was this, the 50s?), nominal 550V (5 times as much) became 600V. | (Even today so many people describe something like an electric dryer as | using "two twenty")

And you know many of them weren't even born back then.

What was 277 back then, 254?

| I know 550V was once used in the turn-of-the-century "mill" buildings | in Massachusetts as an electrician neighbor has mentioned it and I've | seen marked 550V knob-and-tube(!) wiring still in use in the 90s. I don't | know if 600V is used here or if everything is 480V now.

A place I worked at in Texas years ago was supplied power at 600Y/347 and transformed inside to 208Y/120. The largest tenant apparently needed it for some reason. I don't think it was a commonly available voltage. I assume it was a special need or legacy situation. They did do a transformer upgrade while I was there but I never obtained the specs on it.

575V/347 and 208Y/120 distribution is pretty much the defacto standard in most parts of Canada. Wondering what the most common distribution voltages are elsewhere and how they came to be the common operating voltages in those particular parts of the world?

Aside from the interesting tangents on voltage distribution, you have

2 issues here.

1) convert 220V to0 550V single phase. You can do that part with a transformer. it should not be much of a problem there, just go to an electrical distributor and explain that you want to get a boost transformer that will take 220Vin, 550V out. If you got a 230V to 575V that would be fine, the ratio is virtually the same. If you get a dummy behind the counter who can't think, tell him you want a transformer that goes from 575V to 230V, he will understand that, and then hook it up the other way, it makes no difference. For a 3HP 3 phase motor, get a 7.5kVA transformer, should be fine, but no smaller than that.

2) Convert 575V 1 phase to 575V 3 phase. If all you are going to do is run a motor, the simplest method may be to buy a 5HP 575V rated VFD. You will need to oversize it like that to be able to run the 3HP motor from a 1 phase source. Just make sure your VFD does NOT phase input phase loss protection. The VFD just uses the incoming line power to feed a rectifier to charge up a DC bus, then it uses an inverter to recreate a 3 phase output for motors. It technically does not need or care if the 3rd leg is connected, but it will make the ripple larger on the DC bus, so oversizing the VFD provides sufficient capacitance to smooth that ripple. Also, the rectifier section will pull more 1 phase current than the inverter puts out in 3 phase by the square root of 3, so multiply the motor current by 1.73 to get the 1 phase input current, and that is the minimum size of the VFD you will need.

By the time you are done with all that, it will probably be easier and cheaper to go buy a 3HP 230V motor!