How do those 2 Speed Three Phase Motor s Work?

I hope I am posting in the correct forum. Did a search on net and couldnt find much on this. I have a 2 Speed 3 Phase Motor in my SB lathe. The name plate says it has two windings. 6 leads coming out of it T1 T2 T3 and T11 T12 T13 I am wondering how the motor is hooked up for high and low speed? Seems to me they run one winding for high speed and both windings for low speed. Is that right? So high speed would be the lower horse power rating right? Thanks for the help Skate

How about a photo of the nameplate?

Yes, the more poles (read: windings) in a 3 phase motor the slower the rpm of the stator

You will need a three pole, double throw switch. It will take your line voltages, L1, L2, and L3, and direct them to either T1, T2, and T3, OR T11, T12, and T13. Hooking up your voltage to both windings at once will let out all the magic smoke that the motor contains.

texbuck

They connect two field windings so that they act as one winding, one pole for high speed and connect them so they act like two different poles for low speed.

Do a search on "Dahlander motor". There are other multispeed systems, but chances are that it is a Dahlander.

Bill

If the hp rating scales like the speeds then it is indeed a consequent pole (dahlander) type
motor.

The high hp goes with the higher speed rating.

There's a special drum switch or contactor setup to run these. There
will be an extra couple of poles on the switch which shorts one tripet
of windings in one speed range.

There are plenty of motors with two separate windings, and equal power on both settings. Others are unequal.

We need a photo of the nameplate.

Thanks Much guys for these replys. I am not sure how to post pictures here yet. I will work on that.
This Lathe came with two sets of three push button switches. One set is high-low-off the other set is forward-reverse-off It has 4 contactors. I figured two contactors are for forward/reverse and two are for high/low. Dont know for sure. Anyway here is the info off motor nameplate. Will try to put up a pic soon as possable.

Multispeeed motor
Type-OGMX serial# 2182066
220 Volt 3 phase
60 cycles 40 rise
Frame 224
code G 2 windings
1.5Hp .75HP
Rpm 1700 840
The Louis Allis Co.
Milwaukee WI

Ok I will search for dahlander and see what I can find and also try to get nameplate pic up quick like. Thanks skate

Okay an update I just went to Wikipedia-Dahlander motors. I think I understand how it works now. I see they hook windings in a delta with two windings in series each phase for low speed and two parallel Wyes for high speed. I guess I could think of each winding as a pole and when they hook them wye the poles are farther apart so motor goes faster right? So it just takes twice as much HP to run the motor twice as fast right? Now I'm thinking mabie it would take 3 contactors to switch the windings from high to low but i gotta ponder that a little more. Only 4 contactors in the lathe. I am trying to decide weather to keep this motor in this machine or put a new one in with a VFD

Thanks again skate

I recently put a VFD on a Dahlander spindle motor on a cylindrical grinder. I left it connected for high speed and slowed it with the VFD. The HP output is the same connected for low speed or with the VFD at 30 cycles, so all it required was one contactor and one speed control, about as simple as it can get, important because it is in a shop where anyone may run it.

It did get a little tricky because the power needs to be left on for braking after the operator switches it off. I used the a switch that closed the contactor through an auxillary relay and sent a run signal to the VFD with another pair of contacts. Switching off shuts off the run signal immediately, sending the VFD into braking mode. A capacitor on the auxillary relay holds it closed for a few seconds, keeping the power on for braking, then it opens and everything is shut down. All the operator knows is to switch the spindle on and off and set the speed.

Bill

Thank You for that reply Bill. I may just try that. It would be alot simpler than lining up the new motor, drilling holes new holes for it ect. I see they have inverter rated motors now for use at frequencies over 60hz for vfd use I guess. Do you think these older motors will hold up to the frequency variations very well? I appreciate the description of the circuit you used in above example. I am used to thinking of motors controled by contactors/starters and I just bought my first vfd to play with. There is no contactor in the diagram in the manual so the vfd handles overload- on/off duties I guess? I take it in your example you wire the contactor ahead of vfd? Is that redundant or in other words could you run it without the contactor? Its all interesting to me Thanks again skate

Correct. It is considered poor form to switch the output of a VFD, although I gather that later ones are more tolerant that way. JST can offer more on that than I can. It would not be necessary to have a contactor at all but then the VFD would be lit up all the time. The contactor will last a long time since it is closing and opening on only the current drawn by the VFD's circuitry, not the motor starting surge and inductive load on the break.

In this case I was under some severe constraints. Someone else had installed the VFDs in a setup that worked but required a night school course to run. You first switched on the contactor, which lit up the VFD, then started and stopped with the VFD buttons and to change speed you had to go to the VFD program and change the parameter. The spindle and wheel setups were similar but not quite alike so the operator had to learn each separately. Then the clown who did it departed, stealing a $600 solderless connector crimper as he exited. As you can imagine, I inherited a mess and an owner who was one step away from a screaming tantrum. Just to make it more fun, the internal wiring in the machine was in formerly flexible plastic sleeving that had atrophied over the years, making it nearly impossible to add wires. My assignment was to make the controls all work in the normal manner with a knob to set speed on each motor.

It has a 24 VAC control circuit, so I rectified some of that for the DC to run the delay relays. When not running, only the 24 V circuits are energized.

Since three of the motor wires were not used, I repurposed them for controls.

Re motors running at higher speeds, I haven't had a problem, but I have not converted that many. Once again I defer to JST. I did program the motor on a little Harrison lathe to 180 cycles and it has been running fine. The instructions for doing that are not in the manual. After some badgering, tech support for the VFD gave me the undocumented access code to alter the maximum frequency. I had some doubts, but the guy who signs the checks wanted it.

Bill

"There are plenty of motors with two separate windings, and equal power on both settings. Others are unequal.

He had mentioned that the hp ratings were not equal in an early post. This is strong suggestion it's
consequent pole. Most dual winding motors tend to be equal hp rating on the two speeds. Never
seen one that wasn't.

Bill's approach is the first go-to when running a motor like this on a VFD. Caveats: motor might smoke
eventually if it's older with sketchy insulation, being run on the VFD waveforms. And it might detonate
if run ten percent overspeed.

But smart money says it will run fine forever on a VFD and can be run at least 50 percent overspeed with
absolutely no ill effect.

Bottom line here is, it's a motor. Motors go to heaven for all *sorts* of reasons, and when they do you
replace them with a new one. Run it till failure.

P. S. I left off a logical conclusion. You could simply have a main power switch that you turn on when using the machine and and eliminate the timer. Since you are using the machine yourself, not a shop full of people, you can just remember to turn it off when through. Then you can control on-off and reverse with switches connected to the VFD. One of the constraints in my example was that someone could switch off the spindle and wheel, then walk away without any further action like turning off a master switch.

We used Allen Bradley pots, expensive but well suited to a hostile environment. You probably can set a multiplier on the frequency display to make it read RPM.

Bill

jim rozen said:

He had mentioned that the hp ratings were not equal in an early post. This is strong suggestion it's
consequent pole. Most dual winding motors tend to be equal hp rating on the two speeds. Never
seen one that wasn't. ....

Click to expand...

Maybe that was a statement... seemed more like a question as in "that's how these work, right?".

In any case, we got the information, and it does seem like a regular Dahlander type, based on the information.

We recently had a thread on a motor that was two winding same power. They easily can be, or they could be different, it depends what is wanted by the application, as well as on the amount of oversizing of the motor, and the proportioning of the windings as far as slot space.

Whenever the motor is equal power, it necessarily will be a lower power than it could be in the same frame. If unequal, it can be closer to full normal power for the frame size, and there is a chance that the slower speed may not need as much power anyhow.

However, the Dahlander uses the slot space the most efficiently, as it always uses all the windings. As it makes for lower power on one, there is little reason to do that with two windings. The best reason to use dual unequal windings is to use a much cheaper and smaller switch, for speed switched machines in which the slow speed can tolerate less power.

That's what you get with a VFD after all. Less power at slower speeds.

That nameplate clearly states it is a 2 speed 2 winding motor. A Dahlander is a 2 speed 1 winding motor, what we call a 2S1W Consequent Pole. That is NOT what this motor is.

In a 2S2W motor, there are simply two entire sets of windings, in this case one is a 1-1/2HP 4 pole winding, the other is a 3/4HP 2 pole winding. The torque is the same in either one, but because of the different number of poles, the speed is different by a factor of 2. But only one of them is connected at a time. You essentially have two separate motor starters that operate it, one for each winding.

This diagram shows Full Voltage control, so that's something to adapt, but it give you the concept from a power standpoint.

OK, but the philosophy is still the same. A VFD connected to the high speed winding will deliver the same power at half speed that switching windings will give, so he can leave the VFd connected to the high speed winding and control it over the same range.

Bill

First off I have to say you guys are teriffic. I've learned much from this little thread.

Bill Yes understand its best not to switch the output of a vfd and I wont do that. Probably just turn it on and off at the disconnect (line side) when I use the machine. I appreciated the rest of the story on the grinder. and the little lathe motor running at 120 hz thats good to know so I'll try that in future. I've wired many VFDs, but programming them is new for me so Thanks for the info about the multiplier to read motor rpm. I was wondering how I was going to do that. If i use a vfd with this motor I will run it on high speed like you say. Then experiment with which position to run the belt for the speeds I want.

Jim I was thinking they run one set of windings to make 3/4 hp and both sets to make 1.5 hp. So both windings would be the same. That just made sense to me then. I'm not so sure now. Thanks for the info that " old motors should last forever and you can usually run them 50% over speed on a vfd. That gives me a little incentive to give this one a try. This motor is a brute for only 1.5 hp and i bet it has bearings which prob. need serving as its from 1956.

JST Yes my statement was a question. Thanks for the good info. I do like the idea of the dahlander using all windings all the time.

Jraef Thanks for pointing out the dahlander is a 2 speed one winding motor and that mine is probably run one winding at a time. So I take it the 3/4 hp 2 pole would be high speed but lower torque than the other winding right?

Well this has all been interesting. I've got enough info now that I will find out what type motor this is by ohming it out. It makes sense to me it is run with one winding at a time because the lathe had 4 contactors and I am used to seeing 2 for reversing so the other two would be for speed. Turn one or the other on depending on what speed you want. From what I could figure out wiring it dahlander configuration would take 3 contactors. So that would take 5 contactors total. I've got a 2 hp vfd so I think I will give that a try, if I can figure it out. Just for testing to get it running I'll wire it to a circuit breaker. I will report back with my findings on what kind of motor it is. Thanks again to all you guys who answered my question. skate

Ok today I checked the windings of this motor one set were all 4.5 ohms between phases, the other set were all 7.5 ohms between phases. There was no continuity between the two sets and since the windings are unequal it must not be dahlander type and would seem to be the two separate winding type where only one winding runs at a time. I would have thought one set of windings would be closer to half the ohm value of the other one. Anyway if I run only one winding off a vfd I would want to use the high speed and at only 3/4hp for a 13" lathe it doesnt seem like much power but thats the way they ran it originally so mabie so. I suppose I should continue this on the SB lathe forum. Thanks Much fellas for all your help.

"That nameplate clearly states it is a 2 speed 2 winding motor. "

So it does. Thanks for the clarification. I was fooled by the fact that the hp rating nearly
scaled with the speed.

The best approach is to run only one winding, the higher hp one, with a VFD.