Compressor motor

[JaysNJcub127]

Hello all. I just acquired a large air compressor and it's probally between 80 and 100 gallons. It has a duel piston pump. There is a 3 phase motor on it that will have to be replace ld with a one phase. How would I go about finding out what hp etc I would need to replace it with?

[gcbailey]

does the motor have a spec tag on it? I know my dad's 80 gal 3 phase has a 4.5HP motor, it is pretty old so I don't know what a newer one would have or if that's something that has pretty much been a constant.

[ol'George]

Originally Posted by JaysNJcub127

Hello all. I just acquired a large air compressor and it's probally between 80 and 100 gallons. It has a duel piston pump. There is a 3 phase motor on it that will have to be replace ld with a one phase. How would I go about finding out what hp etc I would need to replace it with?

Just a thought.
Sometimes retaining the origional 3 phase motor & building a rotary or static phase converter is cost effective if you have single phase 220 Volt power available in your shop.
It all depends on your abilities and just how big a motor that is on it now.
if you are talking 5 hp or more, they can get quite pricy for a 220V single phase replacement.

[brentwd]

You can take a phase converter and convert the power going to it. As for the other, a roto phase will not run the compressor once it has built up pressure. Go with the phase converter. I have made a roto phase for my band saw, but the 3rd leg of the converter is weak and will not run the compressor. I was told this by the guy I got the plans for the converter. I hope this helps.

[JaysNJcub127]

well, i was looking at phase converters and they seem to be about as much as a new single phase motor. I guess the best way would be to get the spec tag off the motor and have it matched up and see what would work.....

[rmunro]

Advice. Note the motor RPM. I didn't. The 3 phase was 3500RPM, and I replaced with 1750. Worked, but not great. Took another look at the old motor, saw my error. Got a 3500rpm, and, magic.

[JaysNJcub127]

ok Well went to check out air compressor and to my suprise its a 1 phase !!! yay !!! I cant seem to find any info on this motor though.

its a
Fairbanks Morse
Repulsion Start
1ph 220v 6.9 amps
hole mount sk203
number on tag is 439749

and its BIG

[ol'George]

Originally Posted by JaysNJcub127

ok Well went to check out air compressor and to my suprise its a 1 phase !!! yay !!! I cant seem to find any info on this motor though.

its a
Fairbanks Morse
Repulsion Start
1ph 220v 6.9 amps
hole mount sk203
number on tag is 439749

and its BIG

It might be physically big but not in H.P. according to those ratings.
Example:
My compressor motor is 3Hp, single phase, 220V. drawing 16 amp.rated load
Are you sure yours isn't 16.9 amps?
My motor is about 12" diameter and 16 " long, (215 frame) ( 40 yr old Ind. motor)
full of copper windings not these whiz bang china knockoffs.

[JaysNJcub127]

Originally Posted by ol'George

It might be physically big but not in H.P. according to those ratings.
Example:
My compressor motor is 3Hp, single phase, 220V. drawing 16 amp.rated load
Are you sure yours isn't 16.9 amps?
My motor is about 12" diameter and 16 " long, (215 frame) ( 40 yr old Ind. motor)
full of copper windings not these whiz bang china knockoffs.

yes, 6.9 which makes perfect sense for 1hp, what I am reading is that repulsion motors work a little different........ I guess we will find out

[ol'George]

Originally Posted by JaysNJcub127

yes, 6.9 which makes perfect sense for 1hp, what I am reading is that repulsion motors work a little different........ I guess we will find out

1 ph = single phase, is not the same as 1 HP.=horsepower
if it is 1 hp, it is not a " big motor" but I guess it is all in what a person is comparing it to.