I wonder if it is a DC motor, and the 'dual voltage' is the range of voltage giving variable speeds?

A DC motor is likely to have brushes, in holders towards one end of the cylindrical case. Might be at right angles or opposite. In this case, there will also be a speed knob on the control box, and some electronics too.

A DC motor will not work on AC, so it also has a rectifier in the electronics, but this rules out your plan to use a Variable Frequency Device.

You don't say what reason you have for the change – so please explain. If your existing motor is playing up, there may be answers which meet your needs without a complete re-design.

Regards, Tim

My lathe was fitted with VFD before delivery, and it is very handy (Really am almost too idle to change belts) BUT

Reducing the speed this way reduces torque, and the speed of the cooling fan, so the motor could run hot on heavy low speed cuts. You never get something for nothing.

Your three phase motor will probably need to be dual voltage, and have the windings connected in the correct way (Can't remember Star or Delta)

Someone will tell us!

Occasionally, I manage to summon the energy to change belts on the single phase Mill/Drill, to change speeds, so a VFD is a nice to have rather than a necessity.

Howard

Edited By Howard Lewis on 21/10/2017 15:42:12

Whether it's a DC or induction motor, the key thing the plate says is "1 phase". So no, you can't use it with a VFD. = Variable Frequency Drive.  And if it is a DC motor it probably has a speed controller anyway so you wouldn't need to.

Edited By John Haine on 22/10/2017 10:29:27

.

Really ?

**LINK**

http://www.invertekdrives.com/variable-speed-drives/optidrive-e2-single-phase/

MichaelG.

Interesting link Michael.

But it looks to be a somewhat limited device.

Page suggests its intended primarily to reduce wasted power consumption in pumps and similar when running below their rated load. Non-reciprocating pumps and fans tend to have a very rapid delivery / power consumption drop off when speed falls so the actual speed range variation needed in practice to match power to load probably isn't great. Also says conveyor systems. I imagine motors on such are inefficient when running lightly loaded so a VFD could well manage power consumption better than the motor does itself at low loads. There is a lot of literature on this sort of thing concerning 3 phase VFD applications.

Shaded pole motors tend to have pretty horrible power efficiency at the best of times so almost anything is going to be an improvement. Despite efficiency being even worse when running at other than the rated speed you could still end up using less energy overall.

Surprised that split phase capacitor run motors are recommended as, naively, the permanent capacitor would be expected to make it very frequency sensitive.

Clive.

Single phase VDFs do exist and operate in exactly the same way as a 3 phase VDF. There is no theoretical or practical reason for them not to work!

The problem is finding one at a reasonable price, They are a rare bird, as there is little call for them. That they exist is not in doubt. In fact I have one that I use on a single phase Parvalux induction motor. It is an old device and it appears to have been made by ABB, at least that is the name on it.

It isn't the greatest of VDFs as the speed stability is a bit dodgy. I found it in the scrap bin when I was working for a large company, so that might be the reason for the poorish speed stability, i.e. it has a fault.

Andrew.

Andrew

I think the major issue against single phase VFD devices is start up problems. Can't have anything with a centrifugal switch on the start winding as it will drop in if slowed down too far. I suppose you could bypass the switch but that makes installation more complex and driving the start winding isn't going to be trivial as driver characteristics need to be somewhat matched to the motor. Especially when starting and running at low speeds. All do-able but makes for a complex device. Especially before cheap micro-controllers.

Realistically connect and play is limited to shaded pole and permanent split capacitor motors. Which aren't the most common of devices as the inherent characteristics make them unsuitable for general purpose use. So, unlike the 3 phase VFD situation, there is no vast installed base of standard technology that could happily adopt an electronic speed control system in place of, or additional to, standard mechanical methods.

If you are going to have to change motors might just as well get a standard 3 phase and be done with it. Probably cheaper to although the low powers normally associated with shaded pole motors aren't generally available. But DC motors are common at such low powers and generally much better at the variable speed bit than any shaded pole motor can be. Primary advantage of shaded pole motors is that they are a relatively cheap, simply plug into the mains, device for low powers. Putting a VFD control box in front of it pretty much wipes out any possible cost advantage over a DC motor so a very compelling reason is needed to use a VFD.

My guess is that Andrews motor was part of a system made for use in explosive, or explosive risk, atmospheres. Commutator sparks from ordinary DC motors not being desirable in such situations and truly gas tight motors very expensive.

Clive.

Hello Clive,

I am not advocating single phase VFDs, quite the contrary! if you look at my initial response, I strongly recommended changing motors to a 3 phase unit and using an ordinary single phase to three phase inverter!

John Haine, said that you can't use an inverter on a single phase motor. I was just pointing out that there are inverters which will drive a single phase motor. My ABB inverter isn't particularly good at starting under much load and does appear to have a fault, as the set speed varies somewhat. So they do exist, but really NOT recommended!

Andrew.

.

Neil,

My response to Clive refers

MichaelG.

Kevin

Yup no problem but it would be wise to set the internal current limit and other parameters to appropriate values for the smaller motor rather than run it with the as supplied default settings. Probably not functionally necessary but safer should you have a problem.

Worst thing about adjusting parameters is understanding the manual. VFD manuals are notorious for being hard for the non specialist to follow.

Clive.