Speed control for a 220v 1PH 3HP AC motor?

Pcmaker

Pcmaker

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I'm tired of waiting for Precision Matthews. I was told they would have 3 phase motors available for my PM-835S knee mill Januuary of this year. It's halfway through August now and I was told they are not even ordering these motors. I wish they would have been honest with me when I was inquiring before I had purchased the mill December of 2020.

Is there a way to control the speed of a 220V single phase motor? I'm tired of messing with the pulley and back gear just to change the speed. I know you can't hook up a VFD to a single phase motor, but my 120v PM1127 lathe and my PM25MV mill both have knobs for motor speed control.
 
Basically no, there are single phase to single phase VFD's, they requires some rewiring and elimination of the capacitors and the starter switch. I have not heard of any body using these, but you can try. Power delivery? Alternative has been to measure up the motor mounts and shaft to adapt something. I have done this with a few other people on their mills.

Single Phase Output VFD, Control 1 Phase Motor Speed | GoHz.com

www.gohz.com www.gohz.com
 
I don't understand how my PM25MV and my PM1126 lathe both have speed control even though they're 120v single phase
 
They use DC motors, voltage in does not determine voltage out and the type of voltage or motor used.
 
For an "induction" motor, the only way to vary speed is to vary frequency. Years ago(1974) I was working at a plant where a ceramics mixer used a light dimmer to slow the motor down. "Slip" went up, current went astronomical, and speed control went out the window. It did work, sorta, but the cost of replacement motors soon stopped any further attempts. A single phase induction motor usually has a capacitor somewhere. Further, as the motor slows, the centrifugal switch closes on the start winding, swinging speed control (torque) widely.

For a DC motor, the identifying mark(s) is brush holders. These days, even DC or "universal" motors depend on an AC line input. The speed can be varied, widely. But speed regulation is dependant on load and takes a complex electronics package to maintain reasonable regulation.

Assuming the two machine numbers you state are of Chinese ancestry, I would bank on them being DC motors. The only practical solution to the induction motor is to replace it with a DC motor and conrols. Industrial power often uses 240 volt AC to power 180 volt DC motors. There are simpler (cheaper) solutions, often based on treadmill motors. But there is considerable work to make that adaptation.

For commercial motor control, there is usually an "SCR" controller that never reaches 100% throughput. See 240V vs 180V above. They have complete packages ready to install, but have your checkbook ready and well stocked. Motor theory is a complex subject, there are hundreds of books on the subject. And no one book covers all the details.

For all practical purposes, learn to live with changing belts and gears until you are ready to invest the (considerable) work learning and buying the conversion parts.

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I agree with Karl_T. First get the Frame Size of your existing motor and see if you can find a direct replacement motor from another manufacturer. If you can't find a direct replacement, it's likely that you can find one very close to the specifications you need. You already have a lathe and another mill so you should be able to fabricate parts needed to adapt. Food for thought.

Ted
 
The original intent of the OP was that while waiting for a 3 phase motor he was curious why some "120 Volt" devices were variable speed and some weren't. My response was intended to explain in some detail why this is so. He already intends to convert to 3 phase, eventually, my comment was more to point out that changing belts and gearing is not related to a remote control TV. It is simply a part of running a machine.

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Bi11Hudson said:
The original intent of the OP was that while waiting for a 3 phase motor he was curious why some "120 Volt" devices were variable speed and some weren't. My response was intended to explain in some detail why this is so. He already intends to convert to 3 phase, eventually, my comment was more to point out that changing belts and gearing is not related to a remote control TV. It is simply a part of running a machine.

.
Click to expand...
Understood. I was just addressing his frustration of waiting for PM to get him a 3 phase motor.

Ted
 
Pcmaker said:
I'm tired of waiting for Precision Matthews. I was told they would have 3 phase motors available for my PM-835S knee mill Januuary of this year. It's halfway through August now and I was told they are not even ordering these motors. I wish they would have been honest with me when I was inquiring before I had purchased the mill December of 2020.

Is there a way to control the speed of a 220V single phase motor? I'm tired of messing with the pulley and back gear just to change the speed. I know you can't hook up a VFD to a single phase motor, but my 120v PM1127 lathe and my PM25MV mill both have knobs for motor speed control.
Click to expand...


According to PMs website, your PM835s uses the same head and motor as my PM935TS.

I had no intention of waiting for Precision Mathews to get motors in stock, so I used a Helmke Plus 3 phase to swap mine over. It was not a plug-n-play job though.

If your good at TIG welding and don't mind doing some work, it's do-able. the thread is here:

www.hobby-machinist.com

Adapted a standard 100l B5 flange motor to my PM935. It's was a PITA!

But, I got it done. Finally! Anyone else done something like this? If so, how did you do it? I picked up a Helmke Plus 3hp 3 phase motor on ebay. It was 200$ with free shipping from Germany. Kinda baffling that they could sell a 40lb motor, and ship it from Europe for that price. Oh, and...
www.hobby-machinist.com www.hobby-machinist.com

Another possibility. There is a seller on ebay that appears to have a similar, if not identical 3 phase motor listed for sale. I've never bought one of these motors new from PM, so no idea how they're priced, but this price seems absurdly high compared to the $200 I paid for my Helmke.

www.ebay.com

REPLACEMENT MOTOR for Bridgeport type IMPORT MILL 3HP 3PH step pulley VSM3-SP | eBay

3HP 3PH STEP PULLEY MOTOR. REPLACE YOUR IMPORT BRIDGEPORT-TYPE MILL MOTOR WITH ANEW MOTOR AND SWITCH. MAKE YOUR 8 SPEED MILL INTO A 16 SPEED WITH THIS TWO SPEED MOTOR. DRUM SWITCH HAS HIGH AND LOW SETTING SO YOU CAN SET THE SPEED OF YOUR CHOICE WITHOUT HAVING TO CHANGE BELT.
www.ebay.com
 
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