Wanting to change 3 phase motor to single phase motor on a Coltri MCH-16 Compact

[dchango]

I have a Coltri MCH-16 Compact with about 550 hrs on it, and is currently running a Baldor 3PH motor with a Phase-A-Maitc static phase converter. The system works well but only spins the compressor at 1061 RPM (my photo tachometer reading) which is much slower than the rated 1550 RPM. This is from running the static converter that reduces the HP rating 1/3 which makes the motor equivalent to a 5HP motor, also the drive pulley needed to be 1/3 smaller due to it being on a compressor that’s why the 1061 RPM. Like I said, the compressor works well but is a little slow filling cylinders. It is only running at 2/3rds of its rated performance.

Here is the plan, replace the Baldor 3PH motor with the Leeson single phase motor. Change pulley to an 8 inch one, which should bring the RPM’s back to the 1550 RPM speed. I found the motor on eBay for $419 which was the cheapest. Wiring the 3PH contactor for single phase looks pretty straight forward, so that shouldn’t be a problem.

Current: Baldor Motor M3219T-8, 7.5HP, 3450RPM, 3PH, 60HZ, 184T, 3628M, OPSB, F

Planned: Leeson Single Phase Motor 7.5HP, 3450RPM, 184, DP, 208-230V, 60HZ, Auto, Rigid C

My question, am I on the right track or is there a better way of doing things?

Thanks
Damon

 

[Wookie]

Your overload protection will be wrong wiring a single phase motor through a 3 phase motor starter. I don't know what to tell you the right heaters to use are, but the ones for the three phase won't be right.

It may not be a big deal. A single phase starter can't be all that expensive, is it?

 

[oldschoolto]

The only thing is the added cost and higher amps to run the single phase over the three phase..

I built a rotary phase converter for my Bridgeport..... It works like a charm.... just had a leg that was 170 volt that I needed to bring down..... The easy way is spend the money and enjoy the diving...

Jim....

 

[frogman62]

I looked on the net and found the $419 leeson motor. Here is the problem -- it is a 184 frame which is too small for continuous duty on your compressor. You need the 213T frame if you are going to run the compressor for an hour or two every time you pump cylinders. The 184 frame will get very hot. The 3 phase starter will handle the single phase easily but you may need to change the overload protection. Single phase 220 volts connect to L1 and L2 -- use a jumper to connect T2 to L3. connect T1 and T3 to the single phase motor leads.
Jim Shelden

 

[vincent54]

You'll need a capacitor to start the single phase, and the motor will wear out very quickly. Stick with a new balder, Grainger has them , BALDOR ELECTRIC Motor, 3-Ph, 7-1/2 HP, 3450 RPM, 184T, TEFC - General Purpose AC Motors - 39E468|EM3616T - Grainger Industrial Supply
Baldor motors should last a lifetime. You might try taking it into an electrical motor repair facility to see if the windings are in good shape. It may have a winding thats shorted and can be repaired. It also could be a bearing issue, but doubt it. A new three phase will be 3-4 times the price of a single phase motor. It will work fine for a short while, but the single phase motor will burn out.

 

[dchango]

Thanks Wookie, from what I read about using a 3 PH contactorfor single phase, you are correct on the overload protection. What you need to run T1 thru T2 then to the motorand then T3 to the motor in order for the overload protection to work. At least that’s what found on the internet,and they can’t put it on the internet if it’s not true…………. Bonjour (stolen from the State Farm commercial)

Thanks
Damon

 

[dchango]

Jim, thanks for the info. The Leeson motor that I’m looking at is listed as continuous duty and it is a 184T frame, also Baldor motor that is on my compressor now is a 184T frame. Does it make a difference that it has a T on the end? I don’t know, you know more about this stuff then I ever will, that’s why I ask. Here is the link to the eBay add.
http://www.ebay.com/itm/251270501259?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

Thanks
Damon

---------- Post added October 6th, 2013 at 06:16 PM ----------

Hey Jim, I found this one on eBay 7.5 HP ELECTRIC MOTOR FOR COMPRESSOR 213T Frame 3520 RPM 1 PHASE Leeson, here is the link. 7 5 HP Electric Motor for Compressor 213T Frame 3520 RPM 1 Phase Leeson | eBay



Thanks
Damon

 

[rcontrera]

So you want to do two things ... switch to three phase because that is the power you have ... increase the operating speed to get the compressor pumping right.

Just for reference, the original motor that comes with the single phase MCH16 Compact is a pretty stiff $1548. So, getting a motor that will work for less than half is a pretty good deal! Just make sure that it will fit in the case. When we build a single phase Compact, we have to put it in a slightly bigger case because our single phase motor is larger than the thre phase motor.

 

[lowviz]

The only thing is the added cost and higher amps to run the single phase over the three phase..

I built a rotary phase converter for my Bridgeport..... It works like a charm.... just had a leg that was 170 volt that I needed to bring down..... The easy way is spend the money and enjoy the diving...

Jim....

Seriously!!! You ARE old school. Next time, try these guys: TEMCo XR2 PC0002 - 3HP Rotary Phase Converter Converter CNC Single to Three - 208 220 230 240 V volt

Works like a charm for my Clausing Mill. This thread is fun to watch...

...//... just had a leg that was 170 volt ...//...

-erm, I think that is called the "wild leg"

 

[oldschoolto]

Seriously!!! You ARE old school. Next time, try these guys: TEMCo XR2 PC0002 - 3HP Rotary Phase Converter Converter CNC Single to Three - 208 220 230 240 V volt

Works like a charm for my Clausing Mill. This thread is fun to watch...



-erm, I think that is called the "wild leg"

So I should have spent $350 plus shipping on a inverter that's to small to run my Bridgeport ???? Why ??? I built mine for less than $75 bucks ... I get much pleasure from doing it myself.... I'm of the old school ... Not what you HAVE, its what you built...

And yes.... I do know its called a wild leg....