3 Phase 110 VAC 1/4 horse power motor

[ACDC]

A artist friend asked me to look at a motor he bought from India that is labled
3 Phase 110 VAC 1/4 HP. It has three wires coming out of the body.

When it was ordered there was a lot of confusion about the voltage and he
thought he was getting a 110 VAC single phase motor.

Searching the internet it appears that 3 phase 110 is rare or may not even exist.

Any one ever deal with this type of issue?

Maybe they just sent a 220 motor 3 phase motor and remarked as 110, but then
where do you get 3 phase 110, it's just cheaper to replace the motor.

I'm fairly sure you can't rewire this, from the three wires to operate on 110, but
then I'm not an electrician either.
Any help would be appreciated.

[MrAl]

Hi,


120vac line to neutral (four wires) is 208vac line to line (three wires).

You really should get the spec's from the manufacturer though, or perhaps you can post a link to their site and better yet a link to the actual product.

[ACDC]

There is no documentation to post or link to manufacture, it's some
where in India, I agree with more doc's all that would be great.

What I have is a motor with three wires and a lable that says 3 phase 110vac.

But Thanks for the input MrAl.

[MrAl]

Hi again,


Well, as i said, a 120v line to neutral motor would mean 208v line to line, so you would need a 208v delta to power it, at
least that is my best guess without any real data sheet to go by.

If you have a three phase variac that can go up to 208v line to line three phase then i could suggest a few tests to find out
if it is really 110v, but then again i doubt it can be 110v line to line because that would mean 63.5v line to neutral, which is
really unheard of, unless of course the motor was custom built.

If you dont have a variac then another idea would be to connect some light bulbs in series with the three leads and see what happens.
If the motor draws too much current the light bulbs will drop some of the voltage. We can make some measurements to help determine
what kind of motor it is.

The other thing that sounds very strange however is that you are saying that it is 1/4 hp (one-quarter horsepower) but yet it is
three phase. That's an awfully strange thing to see i think because why would you need three phase for a motor that small...
That's roughly 0.6 amp per line phase.
Could it be they messed up on the "3 phase" when really it is one phase with hot, neutral, and ground? Still just guesses at this point.
How many 100 watt light bulbs with screw type base sockets do you have laying around?

[Lenp]

ACDC

OK, Lets assume the motor is really 120VAC 3 phase. Here's a few ways to make it run!
Use a dynamic converter. It's a single phase motor connected to a 3 phase generator (way too costly)
Make a dynamic converter. Use car alternator, with the diodes removed and a motor. Mess with it until it works!
Buy a static converter, again way too much money

Or....
Build a cheap DYI static converter!

Connect motor wire #1 to 120 the VAC feed
Connect motor wire #2 to the Neutral
Connect a motor start capacitor between motor wires 3 & 1 or 2 & 1. The only difference will be the running direction.
BE SURE it is a motor start capacitor. The junk box capacitor, even if it has the same rating will probably explode since they are designed. among other things, for DC. Air compressors and air conditioners might be a salvage area for these.

As soon as power is applied and the motor starts running disconnect the capacitor.

You will need to try different capacitors for best results since there are no specs on the motor, but most motors will start with a wide range of values.

The motor should run, but, with reduced horsepower. It may also not start under a large load since the torque is diminished.

There were a group of photo processors around that used 3 phase motors and they were all converted to single phase operation. They used a timer relay to open the capacitor connection a second or two after the motor was powered. If you do that be sure to use adequate contacts for the capacitor since the arcing and current could be quite large.

Anther option is to try to locate a VFD (Variable Frequency Drive). These takes single phase AC and generate variable frequency 3 phase for motor speed control and a host of other programmable options.

Side note: Some newer washing machines are using 3 phase motors and a FVD to 'customize' the machine speed for custom wash cycle, cheaper than a gear box!

Hope this helps!
Len

[Robert Reed]

The first thing I would do is to verify what type motor you have. Put an ohmmeter lead to ground (frame or whatever. Ring out each of the three leads and see if one goes to ground. If continuity on any of them then it is definitely single phase. If it is three phase, then all wires will have continuity between them with nothing to ground.I have seen some strange color coding on motor leads of Asian descent, so pay no attention to that.
Next question -do you want 3 Ph. or single Ph. If it turns out to be a three phase of odd voltage and you really want single phase, I would pitch it and buy another (preferably American) motor. 1/4 HP is a small motor and should be relatively cheap.Of course if this motor is a replacement unit intended for a custom sized space then that does complicate things!

[ACDC]

Thank You Mr. Reed, and to everyone that has reponded.

Tuesday I will check the motor, and if it isn't 110 1 phase we will replace.
We know a new motor size will generally fit, but we're not expecting a drop in
replacement. However a third friend, also involved in this small project,
is a machinist with a mill and lathe.

[Dean Huster]

If it's a 3-phase motor, you'll read the same resistance between leads 1 & 2, 2 & 3 and 1 & 3.

I've never seen a fractional-horsepower 3-phase motor in my area. Anything that's fractional is always single-phase, usually 240v at least.

[dacflyer]

i tend to agree with Lenp as he said here....
Connect motor wire #1 to 120 the VAC feed
Connect motor wire #2 to the Neutral
Connect a motor start capacitor between motor wires 3 & 1 or 2 & 1. The only difference will be the running direction.
BE SURE it is a motor start capacitor. The junk box capacitor, even if it has the same rating will probably explode since they are designed. among other things, for DC. Air compressors and air conditioners might be a salvage area for these.

Me... i have seen some motors that actually also use a start/run relay
so make sure that you ohm out the leads on the motor, one winding might be a start winding, and the other might be a run winding. the run winding will have the lower ohms, the start will have the hightest ohms. if you do not have a start / run relay, you can momentaraly touch the start winding to the power, then release it after the motor kicks over good.
good luck,,,,

[MrAl]

Hi again,


I kinda like the 3 resistance test Dean proposed because it is simple and effective.

I dont think i can agree with the 'motor start capacitor' theory for this motor in particular because it is such a low HP motor (being only one quarter HP). If it was a bit larger like 3/4 HP or 1HP i might tend to think it may be a capacitor start type motor, but it's so small i can see why it would need a capacitor start. I guess it could still be, but i would not expect that with such a small motor. Maybe i should check my Dust Buster to see if it too has a motor start capacitor then (just kidding)

[Lenp]

Al,
If you open your Dust Buster and it really has a start cap, please show me the circuit since mine has a zero phase DC motor


Len

[Texzin]

Yes the 1/4 horse could be a three phase....I use small three phase motors often. most reasons for choosing three phase over single is that three phase is much easier to reverse.

But in my 30 some years as an electrician I have never seen a 120 vac 3 phase motor ( not saying it is not possible ) In The USA it is ether 208 3 phase 60 Hz or 240 3 phase 60 Hz (240 3 phase made up of 2 legs of 120 vac and 1 leg of 240 vac ), 480 3 phase 60 Hz.

[MrAl]

Hi again,


Len:
Oh a DC motor? It must have two start caps then

Tex:
Oh yes, 208v, so i was proposing that they may be giving the line to neutral voltages which would
of course work out to 208v line to line as expected. There's an off chance that they are using the
case as a neutral, but a quick ohm meter test would prove/disprove this.

[dacflyer]

i have some very small blower motors that came out of some equipement, they turn around 3,000 rpms, and they use a small start / run relay. they have a 4" squirrl cage fan on them,.
so i guess almost any size motor can have that.. i have seen other small ac motors also have a start cap on them too. especially desk fans.

[MrAl]

Hi dac,

Was that really a motor start capacitor or could it have been a phase shift capacitor? Some small motors do have phase shift caps which do not really help start the motor as much as keep it running due to the phase shift introduced by the capacitor.

I was just kidding around with the previous jokes though