Variable speed motors

[djjsr]

Does anyone know what the difference is between an AC motor that can vary speed, like a router, and an AC motor with a fixed speed, like a drill press?

I have to purchase a speed controller for the router I have mounted under my router table because the control on the router is difficult to see and I was wondering why something like this can't be used on a drill press.

I really want a variable speed drill press and I'm wondering if I can simply change the motor on the one I have so I can use a speed controller.

 

[lilredex]

Router motors are a "universal" type of motor, they can operate on AC or DC. They are the ones that have a commutator and brushes and can be slowed down.

The other is an induction motor and is started with a twist from a start winding and is designed to run a a specific speed (usually 1725 or 3450 RPM).
If you try reducing the input voltage to slow it, the current increases and it goes up in smoke. That is why you see all those pulleys on a DP.

Google single phase induction motors for other types, etc. The above relates to the common ones.

I have one of these, a Delta 350 and it has a variable width pulley like a Ski-doo or small ride on warehouse sweeper.

http://www.amazon.com/dp/B00006K00I/?tag=atomicindus08-20

 

[darkk]

X2 what he said...

 

[djjsr]

I checked the plate on the motor currently on the drill press and it says it's a 1/4 horse, 1725 rpm, split phase AC motor.

So, if I can find a "universal" brush type motor with the same hp, frame and rpm, I should be able to vary the speed?

 

[Kirbot]

Look up VFD
variable frequency drive

It will let you vary the speed on the motor your drill press came with.

 

[Norcal]

Look up VFD
variable frequency drive

It will let you vary the speed on the motor your drill press came with.

Only if the motor is 3 phase.

 

[Kirbot]

Only if the motor is 3 phase.

I think your right.

I forgot about that.

 

[nehog]

I checked the plate on the motor currently on the drill press and it says it's a 1/4 horse, 1725 rpm, split phase AC motor.

So, if I can find a "universal" brush type motor with the same hp, frame and rpm, I should be able to vary the speed?

You won't find one...

The solution is relatively simple. Find an industrial DC motor (they are typically 90 volts) and an industrial DC motor controller (they are relatively universal, so they work with motors from fractional HP up to several HP). You'll have to adapt a mount (again you won't find the frame you want in a DC motor,) but that should not be impossible.

This is what I did with my small lathe, and it works wonderfully. No belt switching, just spin the dial. The controllers are relatively full featured too, they will allow such functionality as controlled spin up (ramps up the RPMs so it doesn't try to start at full speed), and they 'monitor' speed by looking at motor current and adjust the power to the motor to try to keep RPMs constant.

Around here, I got to a place called ESS in Manchester, which does surplus stuff (much electrical in nature, but other odd-ball stuff too...)

 

[Doozer75]

I really gotta tell ya. A VFD and 3 phase motor is really the way to go. The smoothest running and most versatile. They even make 120v single phase input to 230v 3 phase output VFDs. Better than DC motors, better than universal motors, just better. Still, people are afraid of what they don't know. That's why some people shun fuel injection and keep lovingly stroking their carburetors. Try a VFD and I guarantee you will love one.

--Doozer

 

[robertlynk]

Norcal you are mistaken
Yaskawa makes single Phase drives. They make them for rebranders also.
For example, Electromotive,and P&H among others
there are other drive manufactures out there that make single phase drives also

 

[Norcal]

Norcal you are mistaken
Yaskawa makes single Phase drives. They make them for rebranders also.
For example, Electromotive,and P&H among others
there are other drive manufactures out there that make single phase drives also

A lot of companies make 1Ø input drives but you still need a 3Ø motor.

 

[djjsr]

It just seems odd that considering the easy availability of variable speed power tools, that there is not a lot of variable speed drill presses. I use the same drill press for a wide variety of materials and I would much rather turn a knob than move a belt to another pair of pulleys.

 

[lilredex]

Those power tools (drills, routers, sabre saws, etc.) all use universal motors, so it is easy and costs little to make them variable speed.

Another simple option is to find a two speed motor. I put one on my wood lathe and with all the pulleys it has six speeds and reverse. Believe the motor is 1725 and 1140 RPM. Another option is that variable width pulley in my first post.

Sometimes tool manufacturers need a knock on the side of the head, to see the light. Think about how long it took to have a DP table elevator and idler pulleys installed as standard equipment. It wasn't until things started coming from China that that happened in a big way.

 

[nehog]

One thing to keep in mind is that a 'universal' motor's speed will be much higher than a regular AC motor which is based on the frequency of the line current. So either reduction gears or if you try to slow it down, a much larger motor will probably be needed.