# Help with Electric Motor Identification - Dual Voltage vs Two Speed - 3 Phase AC Synchronous

#### SimpleOne

Joined Dec 22, 2014
12
Hi All,

I have a motor and most of it's control circuit out of an electric hoist, but not the motors name plate. It takes 3 phase AC input, coming out of a nominal 415V installation. I know the motors power rating is 0.36kW as that happens to on the side of the housing.

Coming out of a hoist, I figure it could be either dual voltage or some sort of two speed such as a Dahlander motor (and motor identification is a whole new thing for me). As removed, it was wired in a Wye/Star configuration (i.e. L1 > U1, L2 > V1, L3 > W1 and then U2, V2 and W2 were bridged together).

Is there an easy way to check just by looking at resistance in the windings to deduce if it's say a 380/415 dual voltage motor, rather than something more complex?

The motor has two sets of wires coming out with each set consisting of 3 wires (labelled as U1, V1, W1 and U2, V2, W2). My starting assumption is that these are for the field windings, and represent each end of a given winding (i.e. U1 and U2 are each end of the U field winding). It's not very easy to actually see what's going on with the motor windings due to it's housing unfortunately. Is there a way to identify the type of motor from just the wire ends?

Any help would be appreciated!

#### MisterBill2

Joined Jan 23, 2018
15,609
Mostly hoists do not have two speeds, because the 2 speed three phase switching arrangement is complicated. Do you have any of the controls package? or at least the manufacturers name and the model number? If there are only six leads marked as you describe then it is probably not a dual voltage device. If the connections are all accessible then use an ohm meter to verify that you have three separate windings with no connections between them. That would be the best case. If they are connected then it gets a lot more complicated.

Also, look at the control system, which should have two contactors, one for raise and one for lower. If there is a separate controls transformer for powering the relay coils, it will either be a single primary with two terminals or a dual voltage primary with either four or three terminals. A dual voltage hoist would also have a dual voltage controls transformer. That can tell you what you have.

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Joined Jul 18, 2013
27,609
Hi All,
The motor has two sets of wires coming out with each set consisting of 3 wires (labelled as U1, V1, W1 and U2, V2, W2). My starting assumption is that these are for the field windings, and represent each end of a given winding (i.e. U1 and U2 are each end of the U field winding). It's not very easy to actually see what's going on with the motor windings due to it's housing unfortunately. Is there a way to identify the type of motor from just the wire ends?
It sounds like a typical star/delta terminal connection, the strap across the U2,V2,W2 and connections to the other three indicate a Star connection, Delta would be three straps vertically with the 3ph supply to each strap.
Max.

#### MisterBill2

Joined Jan 23, 2018
15,609
Checking wit an ohm meter will reveal if there are connections between the windings.
How much of the controls part does the TS actually have? That could reveal some useful information, quite probably.

#### shortbus

Joined Sep 30, 2009
9,938
Mostly hoists do not have two speeds,
Having worked where they had over 100 overhead 3phase hoists, of different makes and lifting weight ratings, they all had two speeds on the pendant controller. So I say again, what the he!! are you talking about?

Joined Jul 18, 2013
27,609
Checking wit an ohm meter will reveal if there are connections between the windings.
How much of the controls part does the TS actually have? That could reveal some useful information, quite probably.
It would appear apparent that the motor has 3 windings, 6 terminals. with a typical star/delta connection option.?
Max.

#### SimpleOne

Joined Dec 22, 2014
12
Hi Guys,

Thanks for the input, greatly appreciated!

I'll check resistance between the terminals and let you know. Apart from the motor itself, I got this with:
2 x contractors
1 x mini DIN rail terminal strip
1 x transformer
2 x limit switches
And, what looks like either another transformer or an electromagnetic clutch (which seems like it's meant to be mounted just outboard of and below the motor shaft on the motor housing).
I didn't get a control pendent unfortunately, all those were sold in one bulk lot apparently, so no hints there.

I queried them as to what it came out of, and they said it would be from one of their fleet of old GIS hoists (250kg/500kg). All they could say was that it ran on 415V 3P and that they did have both single and dual speed models that they had rented out. I'm assuming the weight rating is just single fall vs double fall, so doesn't really help with motor identification.

I went hunting around and found some old GIS manuals with wiring diagrams, but it seems that within their 3 phase models, GIS do indeed both single and two speed hoists. I'm thinking this was from either an EM25 or an EM50 model, based on how old they thought these were (bought new around mid 2005). The motors are 380/415V rating. I'm not sure that difference would justify two sets of terminals by itself would it, it's not as though it's double the voltage?

The control transformer looked to output ~48V AC, but I'll put it on the scope today and confirm that. The only hint is that the 2 speed models need 3 contactors vs 2 contactors for single speed models, according to the wiring diagram. But it also shows an E-Stop contactor, so either way I should have three or four contactors, so clearly I can't rely on that to work it out

#### SimpleOne

Joined Dec 22, 2014
12
Okay, so in terms of resistance on terminals:

U1 to U2 = ~13.65 ohms (There was variation in readings here, from ~13.35 to ~13.80)
V1 to V2 = 13.94 ohms
W1 to W2 = 13.95 ohms

All the other combinations (e.g. U1 to W1/W2, etc...) are open circuit.

#### MisterBill2

Joined Jan 23, 2018
15,609
Having worked where they had over 100 overhead 3phase hoists, of different makes and lifting weight ratings, they all had two speeds on the pendant controller. So I say again, what the he!! are you talking about?
OK, none of the hoists that I have used had two speeds. Or maybe that was the trolley function that did not have multiple speeds. The hoists were just quite slow all the time.

#### SimpleOne

Joined Dec 22, 2014
12
So, I'm still at a loss on how to determine the answer to this. It's definitely only one set of windings, not dual windings. But whether it's rewireable in Star/Wye and Delta to allow for the 380/415 volts, or rewireable in Star/Wye and Delta to allow for two speeds, I'm not sure.

I'm starting to think that I will just rewire it from Star/Wye under no load, and see if there is a change in speed, or if it just results in an increase in current in the windings and no speed change. I only have one clamp meter, but given that it's a balanced 3Ph load (no neutral) then a change in one of the windings (say U1, connected to L1) should indicate that this is true for all others as well. Easy enough.

The question in my mind now though is, if the current changes (i.e. increases from Star/Wye when moved to Delta, as it would in a dual voltage motor), would that prove it's dual voltage, or does a two speed (pole changing / consequent pole) motor also see a change (increase) in current when reconfigured for the second speed.....?

#### Ramussons

Joined May 3, 2013
1,354
It may not be intended as a 2 speed motor. It may be a Star-Delta config for Start and Run. Especially if the Start is under Load.

#### SimpleOne

Joined Dec 22, 2014
12
Yep, fair point. The only issue with that (presuming this is how the whole show came out of the hoist when it was operational), is that the second set of motor leads (U2, V2, W2) are mechanically bridged together via a screw terminal, not into some sort logic device like a controllable contactor etc. So basically, in it's current form it is Star/Wye and would only ever be that unless you had pulled the hoist apart to get inside and re-wire the thing.

Can't decide if they used the same motor for both single and dual speed models, or if it's just a single speed motor with some sort of dual voltage ability. Your point is valid though, perhaps it's missing parts for a start up circuit, but none of the wiring diagrams I could track down suggested that this was 'a thing' in those hoists.

I'm leaning towards just manually wiring it up as if it were a pole changing, single winding 2 speed and seeing what happens.
If my understanding of those is correct, the second speed would occur when wired in Delta rather than the current Wye. The result would also be true if this was dual voltage (i.e. Delta for low voltage input, Wye for high voltage input).

If it is dual voltage (and the dual voltage really is 380/415), then running it with no load under 415v but in a low voltage Delta configuration shouldn't be a big deal to my mind, just for testing. Just worried i'm wrong and it's for something substantially lower than 380V. If it's not dual voltage and is for pole changing, then I should see a speed change I guess.....

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#### Ramussons

Joined May 3, 2013
1,354
Yep, fair point. The only issue with that (presuming this is how the whole show came out of the hoist when it was operational), is that the second set of motor leads (U2, V2, W2) are mechanically bridged together via a screw terminal, not into some sort logic device like a controllable contactor etc. So basically, in it's current form it is Star/Wye and would only ever be that unless you had pulled the hoist apart to get inside and re-wire the thing.

Can't decide if they used the same motor for both single and dual speed models, or if it's just a single speed motor with some sort of dual voltage ability. Your point is valid though, perhaps it's missing parts for a start up circuit, but none of the wiring diagrams I could track down suggested that this was 'a thing' in those hoists.
What is it IS a 2 speed motor, the lower speed being used between Stop and Run to avoid too much Jerks on the hoist cable?

#### SimpleOne

Joined Dec 22, 2014
12
What is it IS a 2 speed motor, the lower speed being used between Stop and Run to avoid too much Jerks on the hoist cable?
Sorry, not sure exactly what you are asking there, but here's my take:

In two speed hoists, one speed (high speed) is used for lifting/lowering when the distance is big (i.e. just yanking something from floor to roof height) and the second slower speed is for more controlled raising/lowering of the load when putting it down somewhere tight/restricted or to position something more carefully in place etc. In a single winding, pole changing motor, I think the speed ratio is fixed at 1:2 (slow to fast), but perhaps i'm wrong there.

That's just my take, never used one in my life, but makes sense to me and seems to be the general outline based on what i've read.

#### Ramussons

Joined May 3, 2013
1,354
Sorry, not sure exactly what you are asking there, but here's my take:

In two speed hoists, one speed (high speed) is used for lifting/lowering when the distance is big (i.e. just yanking something from floor to roof height) and the second slower speed is for more controlled raising/lowering of the load when putting it down somewhere tight/restricted or to position something more carefully in place etc. In a single winding, pole changing motor, I think the speed ratio is fixed at 1:2 (slow to fast), but perhaps i'm wrong there.

That's just my take, never used one in my life, but makes sense to me and seems to be the general outline based on what i've read.
Sorry, Typo.
What if it is .....

I mean, just like in elevators, start and stop slowly, not abruptly so as to avoid too much of a jerky operastion.

#### MisterBill2

Joined Jan 23, 2018
15,609
It is not reasonable to think this is a synchronous motor because having multiple speeds would require changing the number of active poles. It certainly is an induction motor, by all appearances. And an induction motor will produce different levels of torque at Wye versus Delta connections, because the current will be less in the Wye connection.

Many hoists have a spring applied brake so that they can hold position with the power off.

Elevators generally use an electronic control for the speed. So they are an entirely different case.

#### Ramussons

Joined May 3, 2013
1,354
Elevators generally use an electronic control for the speed. So they are an entirely different case.
That's now. Not in the old days.

Joined Jul 18, 2013
27,609
Sorry, not sure exactly what you are asking there,
If the motor has permanent strap(s) as shown in post 6, then it is only used in one permanent configuration, if both options, star/delta, are in use, then no straps exist.
Max.

#### SimpleOne

Joined Dec 22, 2014
12
If the motor has permanent strap(s) as shown in post 6, then it is only used in one permanent configuration, if both options, star/delta, are in use, then no straps exist.
Max.
No, it doesn't have a typical terminal/junction box like you'd see on larger motors. This is just 6 labelled wires coming out of the motor with bootlace ferrules on each wire. There is a matching terminal strip (mini DIN rail full of Wago push connectors similar to these: https://www.wago.com/au/rail-mount-terminal-blocks/2-conductor-through-terminal-block/p/2006-1201). The push connectors have labels as well and deal with all the control circuit wiring (transformer and fuse connections, contactors etc).

As is, the '1' winding wires connect to the output of the two contactors, which are simply serving to reverse direction in the usual arrangement. The '2' winding wires were just bonded together via a screw clamp thingy (https://www.sparkydirect.com.au/assets/full/30007.jpg?20171026150919). That's how it's currently wired in Star/Wye.