Thread: Variable speed control.

It has to do with the eventual application of the motor you're trying to control. A lot of motor controls are rheostats which control the rpms of the motor by (really basically) cutting the power to the motor. For a grinder, you need to keep the power or else you'll stall your wheel out at the lower levels. I have heard that you can use the controls off a treadmill though! Other than that, VFD is the only way to go.

VFDs are good, but if you don't know how to use them, you should get a professional to do the electric work on it. You can fry a motor pretty fast if you don't know what you are doing, it is really easy to screw up, trust me

well, by the looks of this and my thinking . it's onto a pulley system to control speed . OR take the major plunge into a kmg grinder . my sister has a ton of scrap metal . and 2 welders and i have nephews who know how to weld . the plans for the grinder on this site look good so who knows what a weekend can bring

Originally Posted by jeness

VFDs are good, but if you don't know how to use them, you should get a professional to do the electric work on it. You can fry a motor pretty fast if you don't know what you are doing, it is really easy to screw up, trust me

LOL. Yes it is. I am currently looking for a new 5 H.P. 1720 RPM motor for my dust collector.

That can be used depending on it's specs. What is it's input? What is the output? What is it's nominal load/hp rating? What little I know, I know that there are a lot of variables and you need to talk to a person who is skilled in that trade. A normal electrician may not know, may take someone working in an mfg environment as a line electrician to answer your questions.

If you ever "let the smoke out" of electrical stuff, you can't ever get it back and it's toast. If you figure out how to put the smoke back into electrical oop's, please patent it and you will become an overnight billionaire!

Would not the OP's controller be for a DC motor? Reason I ask is I have a setup I hope to use with a controller and a DC motor salvaged from some old printing equipment. Plugs into 110 AC, but has a box with a rheostat and other electronics and is quite variable by turning a dial inside the box.

Originally Posted by sharptonn

Would not the OP's controller be for a DC motor? Reason I ask is I have a setup I hope to use with a controller and a DC motor salvaged from some old printing equipment. Plugs into 110 AC, but has a box with a rheostat and other electronics and is quite variable by turning a dial inside the box.

Just guessing can "let the smoke out" & be dangerous. Mine has a rheostat and is 220v single phase in, 220v 3 phase out:


I can wire a house any day, but that stuff you have to be specific about. You can have 110v in w/ dc out, 220v single phase in w/ dc out, and of course like mine. Other variables are what size motor the controller can handle...mine will handle a 3 hp motor and I have a 2 hp motor on it. Nothing gets much past warm to the hand after running at 25% of 100% (severe load) for several hours with my set-up.

so here is the unit's label. Will it work ? What motor will it work with ? with the motor loose power as speed is decreased with this motor ? Since I know nada about such things , any help is awesome .

I will send a picture of the back of the unit that details input and output in a few. My sister has tons of metal and I have a nephew who can and has a welder so putting together a 2 by 72 grinder is possible so we will see . pics to come .

Hey, more info . here are the specs . NOTE: Heat sink is required on this model for the following applications
3/4 and 1 HP 90 Volts
All 1.5 and 2 HP

Catalog Number: 174307.00
Description: DC SCR CONTROL - NEMA1 ENCLOSED
Input Voltage: 115/230VAC
Output Voltage: 90/180VDC
Output Current: 10 Amps
HP Range: 90V (1/8-1) / 180V (1/4-2)
Direction: NON Reversing
Enclosure: NEMA 1
Ship Weight: 6 lbs.

and here are the features .
LEESON Speedmaster DC control is a general purpose drive designed for use with permanent magnet type direct current motors. NEMA 1 enclosed drives are suitable for most industrial applications. Most controls have a dual voltage switch allowing the control to be used on 115 or 230 volt, single phase, 50/60 Hertz service. However, the proper voltage motor should be selected for use with the power supply input, i.e., 90 volt DC motors for 115 volt input or 180 volt motors for 230 volt input service. Installation and adjustment instructions are included.

thoughts ?