Another air compressor thread.......sorry.

[welderwink]

So I got a old IR air compressor from a friend who I did some work for. It currently has a 3ph 1.5hp motor on it, that he thinks is no good. I dont have 3ph to check it out on. So what Im thinking of doing is getting a new motor and contactors for it. Finding a motor is no problem, but the contactors are (to me anyway). How do I know what contactors to get because its not like I can rip out the old ones and just replace by the model numbers. Plus I would need to find a schematic and stuff.

I just dont know too much about compressors, so I dont know how the shut offs work, how the starters work or anything about this stuff. Im lost.

 

[930dreamer]

This is only a guess. The three phase contactor have 3 poles, 1 for each incoming wire(line), also three wires out(load). I don't know if you only use two poles if the contactor will operate correctly. with a single phase motor. Can you post some pictures. You could have the three phase motor tested, any thoughts on building a rotary phase converter(RPC)?

 

[welderwink]

Yea I was wondering the same thing about only putting 2 wires into the 3ph contactor. And I havent really thought about the rpc yet. I will post some pics.

 

[Torque1st]

A 3HP 3-phase motor draws 9.5A on all legs on 230VAC.

A 3HP single-phase motor draws 17A on both legs at 240VAC

The contacts in the starter must have twice the capacity for single-phase. It is possible the present contactor will work but not probable since manufacturers pinch pennies.

Your present starter may have single-phase capacity markings on it. You will need a contactor rated for 3HP or more at 240VAC single-phase.

Normally a contactor will have three poles and you just use two for single phase. You will need 10AWG wire and 40A breaker although you might get by with a 30A breaker.

Your local electrical supply house can help you select the right unit from their stock. They may also have a little yellow handbook there with the wiring diagram you need.

 

[welderwink]

The 3ph contactor actually has spots for 4 wires. Although only 3 wires go into it currently. The current motor is 1.5hp. But do i need to change out the whole starter or just the contact? I am probably not giving enough info.

 

[Torque1st]

Take it to your local electrical supply house.

 

[79firebird]

930dreamer you are correct you can use a 3ph contactor no prob we had to do that on the paint booth at work when we moved shops and has been working fine for 7 years now