Variable speed motor

[Hank Merkle]

I want to have a variable speed 1 to 2 hp motor for my lathe. Anyone know a reasonably priced way to do this? I really do not want to pay $300 to $500 for a controler and motor (If I can even get it that cheap)

Is AC or DC better?

What are the drawbacks to either?

Thanks,

Hank Merkle

[Jeff Horton]

Check with The Surplus Center. I bought a 2hp DC motor from them and controller. I don't remember exactly what I paid but it was around $225 for both. Of course you never know what they will have at any given time. I had to buy an enclosure and or course wire the controller but is fairly easy.

Ebay is another place to watch.

Another option is you can buy a 3 phase motor, cheap usually. Then buy a Variable Frequency Drive to control it. I have this on my j-line lathe. At extremely low speeds the torque is low but I don't turn at that low of speed typically. I shopped for a long time for a good deal on a VFD. I think I paid $150 for mine. So this might not be the best option, just depends on if you willing to wait on the good deal to come along.

I imagine your going to end up with about the same dollar in either one. I like the DC drive a slightly better. It 'seems' to have better low end torque but I haven't really used it enough to say for sure. I think it is a toss up between the two when you get right down to it.

[Brad Hart]

I prefer a dc motor and controller myself. Surplus center and friesen electric both have packages around 225 to 250 but you could pay another $50 to $100 in shipping. I bought mine on ebay. I paid $315 or so including shipping for a 1.5hp motor and controller that was ready to mount, plug, and turn.

[Steve Hayes]

What about Grainger?

[Jim Becker]

For AC, you really must go the VFD controller/3-phase route (240v single phase input to the controller) and via surplus, can often do it quite economically. Otherwise, DC is your option. Do be aware that you need to pay attention to torque, especially at lower speeds and that may require you work out an acceptable multi-pulley setup for speed ranges, if your machine doesn't already fit mechanically in that respect.

[Jerry Clark]

I got a DC motor and controller from an old treadmill [free] -- lots of control and torque-- Works great!

[Don Farr]

For AC, you really must go the VFD controller/3-phase route (240v single phase input to the controller) and via surplus, can often do it quite economically. Otherwise, DC is your option. Do be aware that you need to pay attention to torque, especially at lower speeds and that may require you work out an acceptable multi-pulley setup for speed ranges, if your machine doesn't already fit mechanically in that respect.

This is good advice. If everyone in industry is changing from DC to AC (VFD's) there is a good reason. Believe me they are.
They are a little more difficult to set up due to the programming but well worth the trouble.
If you have problems with low end torque with a VFD the there is something wrong with the setup. Typically a VFD is capable of 150% to 300% torque at low end.

[Brad Hart]

What about Grainger?

never bothered pricing them but since it is granger it is bound to be over priced.

[Brad Hart]

This is good advice. If everyone in industry is changing from DC to AC (VFD's) there is a good reason.

and just because everyone else is doing it we should too...

[Mark Cothren]

and just because everyone else is doing it we should too...

Brad.......................

Since Don deals with this stuff every day, making a living at it, and he recommends it (with what I would consider to be an expert opinion) - that's a PLENTY good enough reason. Ya think?

[Brad Hart]

Brad.......................

Since Don deals with this stuff every day, making a living at it, and he recommends it (with what I would consider to be an expert opinion) - that's a PLENTY good enough reason. Ya think?

didn't say his info was wrong, just not enough of a reason to change from what I have or for others to think it is the only option worth doing. An 3PHS AC VFD maybe the top of the line, but it certinly has its drawbacks, and it certainly doesn't mean it is the only game in town.

[Don Baer]

I used to be an applications engineer for a variable speed drive company for over 25 years. Like Don said most applications today are done using AC. The reasons for this are that first AC motors are less expensive to namufacture and when the price of high power simiconductors came down the price of the controllers dropped making AC as affordable as DC. The lower priced AC units operate in a constant Volts/freqency mode which like a DC motor will give you constant torgue throughout the speed range. The higher end units can operate this way and can also deliver what is called constant Horsepower. This is done by holding the voltage constant and increasing the frequency. This is like changing the belt ratio and the speed increases the torque decreases. The advantage to this is that for very large pieces you turn slower and need more torque and for very small pieces you can turn at high speed and don't need the torque since the cutting is being done near the center.

[Hank Merkle]

To everyone! this is what is great about forums - I have experts, garage mechanics and somebody pieceing something together and eveyone weighs in with their openion. no I have some information to chase to see what I will do!

By the way - Grainger, McMaster Carr etc. are VERY expensive. I deal with people like this all the time. They are in the business to hve it on the shelf or get it quickly enough for a person to think "" won't waste my time going elsewhere - I just spend the money." I have used them but only when I have to...

Thanks again fo the help everyone!

Hank