Speed Regulators for Single Phase 120VAC Motors

I would think it may be easier to just reduce the speed via reduction gear....

Thanks for the suggestion but the speed must be variable slow to medium and gears do not support that.

It would be simpler to swap out the motor for a three-phase unit but that would prove too costly to a degree I am not prepared to experience.

I appreciate the thought.

LJ

What about something like this?

http://variablespeedmotor.net/

How about a variac simple and available.

I have three Variacs, "Auto Transformers", but never considered them as they reduce voltage. My memory of this alternative is that while that does reduce motor speed, the amperage on inductive loads tends to skyrocket as the voltage drops. Eventually the motor burns up.

Nice try!

Thanks for attempt.

L.J.

fyi

Three-phase VFD's reduce frequency AND voltage in proportion to maintain a proper V/Hz ratio and provide full rated motor torque over the entire speed range.

A Variac will only reduce voltage. Some motors can be effectively speed controlled on reduced voltage alone. All my power tools can be speed controlled when connected to my 20A Variac. However, full torque is not be available at any speed below rated RPM.

"Motor burn" may occur from running any motor at partial speed because the integral cooling fan may not be able to move enough cooling air at reduced RPM.

http://www.amazon.com/s/?ie=UTF8&keywords=router+speed+control&tag=googhydr-20&index=tools&hvadid=4150141499&ref=pd_sl_94dsmxew53_e

There are single-phase VFDs.

Although most VFD's are designed for 3-phase motors, at least one company does indeed manufacture VFD's for single-phase motors.

http://www.anaconsystems.com/text/opti_e2.html

By the way, the DeWalt Radial Arm Saw uses a capacitor-start induction motor, either 1/2 or 3/4 HP.

Wolfe Machinery Co. carries parts for DeWalt radial arm saws, and might still have a manual available.

Good luck.

For what the VFD costs you could buy a lapidary machine complete....and that's neglecting the max hp rating...I don't think it can be done economically...and reliably...

Many tools in this HP range and lower use a universal AC/DC brushed motor. A router speed control or one of your variacs (if large enough) should work fine.

If it's really an induction motor, then the single phase VFD may be your only option.

That was my thinking too.

Cooling will be a serious issue at slower speeds. May need a blower to disperse trapped smoke when it is released..

Rewinding the motor as a 3 phase 4 or 6 pole motor and using a VFD to controle the 3 phase motor ...

running for extended periods as you would for lapidary work, cooling will indeed be a problem

a more traditional rocksaw arrangement will likely be a better solution

another area of concern cutting fluid, consider using mineral oil, which is less toxic than motor oil