Two Speed Induction Motors

As far as your information, you might have a double speed motor.

You can switch the poles of this induction motor in a 1:2 ratio.

Check Dahlander circuit. (wiki) This will show you how to connect.

In speed 1 you can determine the direction of rotation with helping to turn. Just be careful.

Dear dvmdsc

Many thanks for the pointer. I have looked at the site. Still hoping to have confirmation on another forum that we have a Dahlander motor.

Jim

I wasn't able to find the Wiki page, but found another useful one at:-

Field Swiching Circuit

It shows quite clearly that ALL fields must be used to change the speed. That is what the OP has not achieved. The following diagram shows this clearly.

It also appears that with suitable switching, even more speeds can be achieved if wished!!!! Up to four!!!

Compare with dual voltage connection

Dear Andy

Many thanks for taking the time to improve my understanding of the problem.

Jim Runciman

Thanks.

Of course such nice posts as yours are the REAL reason we all come here......

One winding is your high speed set one is your low speed set and the third one is the start winding.

We need much more info to help you out. What are the two speeds its rated to run at?

reason being some two speed motors run with each individual winding as a speed and others will reverse one set of windings while putting power to both to change the speed from high to a 2:1 reduction or back

Basically that's changing the winding configuration form a 2 pole to a 4 pole or a 4 pole to a 6 pole or a 4 pole to a 8 pole field configuration depending on what speeds the motor is designed for. Most often the start winding is only active while the motor is starting in the least number of poles configuration and then is disconnected by a centrifugal switch once the rotor is up to speed.

Dear tcmtech

Thanks for taking the time to reply.

I forgot to mention this is a 3 phase unit, low speed is 1440 and high speed is 2900RPM. The motor has 6 wires emanating from the frame with 3 field resistances at approximately 25 ohms and the other 3 at approximately 16 ohms.

It uses a rotary switch with a number of bridges or links to energise the appropriate winding

Jim

Are you sure it's not meant to be used in a star/delta configuration for speed control.

Not sure how you obtain 6 different resistance readings from only 6 wires, I would have expected only 3 readings. Unless of course you are taking the readings with the switch in circuit and in different positions which would explain the readings obtained.

Assuming that it is in fact a star/delta setup, then you need to establish the start and end of each winding, which should be labelled ABC-a1b1c1, or something similar which denotes that A is the start and a1 is the end of one coil and so on. The switch should be similarly labelled. Connect the two together and it should work.

If the switch is not labelled, then you will need to work it out so that in the low speed(star) position all of the ends (a1b1c1) are connected together, and in the high speed(delta) position A is connected to c1, B is connected to a1 and C is connected to b1.

If the drill runs the wrong way, simply reverse two of the incoming supply wires to the switch.

Star-Delta does not mean Low Speed and High Speed! The Speed remains the same (That is the Nominal Speed of the motor, which depends on the number of poles only)

GA

I am always surprised how little some others here understand simple motor theory. You are not one of them!!! Happy New Year!!

Happy new year to you and all the contributors.

Thanks

Thanks also.

See you all next year (if not before!!)

Hi Jim,

I see in your reply you say that 'it uses a rotary switch to energise the appropriate winding. In this case switch the supply to the machine off (at the circuit breaker) and then using your multimeter on the resistance range check across the incoming three phases and you should be able to 'see' your two windings when you first switch to low and then to high i.e. the 16 ohm winding and the 25 ohm winding. Check R to S, R to T and S to T.

If you don't find the correct readings I would believe that your rotary switch has become defective and should be replaced.

The readings you have at the motor appear to be correct so I doubt that there is anything wrong with the motor.

Cheers,

Keith

Please explain why a start winding will be needed for a 3 phase motor. It will make entertaining reading for Xmas/New year!!

Remember, they (3 phase motors) are self starting at all times, assuming correctly connected and in working order.

So no start winding.

Perhaps you have confused yourself and mixed up single phase and 3 phase motors in your head?

Please wake up Buddy. No sleeping on the job/alcohol drinking....

Re read the OP's post and then follow things in order.

He does not reveal that it's a three phase motor until post # 4 after I made my post in #2.

My reply is reasonably valid for a 6 lead three winding type of dual speed single phase motor which is not that uncommon for larger single phase drill presses and post drills.

SO why the anonymous posting any way?

Cant bring yourself to show everyone whom you really are?

You wouldn't be Kennyaab6 by chance?

This is a general note of thanks to everybody who made a positive contribution to helping me understand the problem. One of the six wires going into the windings I found to be non continuous which would give the symptoms of two phaseing so I'll box it up with the new link tomorrow and report back.

Although I'm new to this forum I always find it sad to see anonymous oxygen thieves taking the time to criticise those who offer genuine advise.

Thanks again

Jim

http://educypedia.karadimov.info/library/173.pdf
try this - induction motors explained

Hi Jim,

You may like to download the Klockner Moeller wiring manual for reference available at this link http://www.klocknermoeller.com/klockner.moeller/wiring_manual_english.pdf Size is about 6,4mB

Very useful little manual and I have had the various printed versions at hand for the last 40 years of my work in the field.

Cheers,

Keith

As you mentioned there are six resistances in the circuit, 3 (a set) of which can be added in the circuit by rotary switch? I hope I have interpreted your information correctly as mentioned? In that case one each set (for each speed selection) of resistance is to be inserted in the winding circuit to increase the starting torue of the motor. As the starting torque is directly proportional to R/X ratio, hence to inrease this ratio the external resistance is inserted in to the circuit for starting only. once it is started there is no need of external R hence it can be isolated from the circuit and the Supply voltage is directly applied to the winding. Similalrly the six terminals means there are two sets of windings which are forming two different number of poles, for e.g. 2 Poles and 4 poles. As the speed N is (120*f)/p the number of poles (the winding) which is selected by actuating the contactor for the winding to drive the motor at that speed in normal operating condition. Hence I hope in your case f=50Hz hence (120*50)/2 = 3000 rpm synchronous speed hence (2900 rpm actual speed considering slip) and (120*50)/4 = 1500 rpm synchronous speed hence (1440 rpm actual speed considering slip). I hope I answered your querry. please let me know if anything more.

Dear Jim,

Regarding the 2 speed induction motor there is a purpose for its application. Usually it is use on hard material or viscouse liquid for the low speed and after reaching the soft part or non-viscouse level of liquid it can be switch on manually or in auto mode to high speed respectively. I have encountered this type of motor in paper industry wherein it was used as agitator on chemical liquid. You can check the connection of low speed and high speed from the motor itself terminal box or nameplate and the control circuit is similar as WYE-DELTA connection and the only difference is the low speed connection become open circuit and the high speed connection will be connected directly in close circuit by either manual mode or auto mode or both. It will depend on your choice.

If the connection is not available on the motor then you can refer it to ELECTRIC MOTOR REPAIR by Robert Rosenberg,

Regards

Arnulfo Palacio

Normally in multispeed motors the winding is connected in delta, star, double star etc. with corresponding change in number of poles resulting in change in speed and motor power. The change in connection is realised through suitable power contactors whose contacts are connected to the six terminals brought out in the terminal box for achieving the desired connection. I have not come across any such starting arrangement where the rotary switch and external resitances are considered for multispeed application.

Well since its been made clear now that this is a three phase motor the only way I can see that it could be a dual speed unit is that if its designed as a single voltage type with two independent winding sets each configured fore a different number of poles.

If thats true then yes its possible to have two different resistances readings between the different phase connections when comparing each winding set or a possible combination of both windings tied together on one common phase connection.

With the second option that your motor has one leg of each winding set tied together A phase to (Ah plus Al legs) and the switch only changes connection points between the incoming phases B and C on the other two phases B phase to (Bh or Bl) and C phase to (Ch or Cl legs) opposed to isolating all three phases from each winding set.

That would make it possible that you could be working with is a system that is getting by with using s DPDT switch (six switch terminals) to select which speed instead of using a 3PDT switch (nine switch terminals).

Is this clear as mud for the smart asses in the back now?

So where are you having trouble with the order of how the original poster gave the said information relating to his motor and what did I ever do to you to deserve this trollish criticism?

Where in his opening post does he specify it's a three phase motor or for that matter where do you see it mentioned anywhere before I made my post based on the assumption that it was a six wire single phase type motor which is a very common design.

As far as my credentials on how three phase and single phase motors work I think this link speaks well enough for me. http://www.electro-tech-online.com/re-projects/100563-3-phase-converter-schematic-miller-system.html

Its how to run three phase motors on single phase without modifying or rewinding them. That thread has been averaging around 10,000 views a year and is well accepted as being a solid and well proven design of which I created and fine tuned myself.

Got any links to work you have done and donated to the world or just your name instead of hiding behind anonymous poster doing troll attacks?

BTW you have been reported.

Further:

See attached a copy from a Leroy Somer document, showing different types of windings for a 2 speed motor. check if any one matches your motor windings, or might show what is wrong with your motor (open circuit on any of the windings?).

i am affraid, but you have to make the measurements youself.

As pointed out(previous comments), you might have One phase missing or one winding open circuit...

This thread has been fun to watch from my perspective. I come from a somewhat uniquie position, living in the US and having cut my teeth on NEMA stuff, but then spending a lot of time working for European companies (Klockner Moeller and Siemens). This thread is a classic example of people jumping to conclusions but not understanding the bigger picture(s) and differences when it comes to two speed motors.

Here in NEMA world, there are two types of 2 speed motors: 2 Speed 2 Winding (2S2W) and 2 Speed 1 Winding (2S1W). With the 2S1W, there are 3 styles of connections; Constant HP, Constant Torque, and Variable Torque. The motor is the same, only the connection pattern is different, but the nameplate may reflect the difference because of the way the INTENDED use is portrayed.

Outside of NEMA world, I don't think 2S2W exists. Every IEC 2 speed motor description I have ever seen is what is called a "Dahlander" motor. For all intents and purposes, that is the same as our NEMA 2S1W motor: the three connection styles are the same; Constant Power (kW), Constant Torque and Variable Torque, although the power ratios are sometimes different in the CT style.

So if you don't know what you have, here are some clues to help narrow it down:

1. If there are only 6 wires and you know it is 2 speed, you can eliminate the dual voltage aspect. It takes more connections to have 2 speeds AND dual voltage.
2. If there are only 2 contactors involved in the starting, then it is definitely 2S2W, it cannot be 2S1W or Dahlander. They ALWAYS take 3 contactors no matter what because you have to have a contactor that shorts windings together to make the Star pattern at some point. If you have a manual switch instead of contactors, see if any of the contacts short out each other in the switch arrangement, that makes it 2S1W or Dahlander.
3. If you do have a 2S1W / Dahlander motor and you can still read the nameplate, look for the Power Rating. If the power rating is the same, i.e. the nameplate only shows one power rating, then it is Constant HP (kW). If there are two power ratings, then it is Constant Torque(HP or kW) or Variable Torque and now you must look at the ratio. If it is 4:1, i.e. the nameplate says .5HP / 2.0HP or 0.25kW / 1.0kW, then it is Variable Torque. Anything else and it is Constant Torque.
4. If you don't know even that much because the nameplate is missing (in which case how would you know it was 2 speed at all?), then look at the application. Constant HP is typically used on machine tools where the load torque requirements will vary inversely with speed; i.e. the cutting bit will be biting more material at a slower speed, so you will need MORE torque. Constant Torque is typically used on things like conveyors, compressors, positive displacement pumps etc where the torque requirements of the machine stay the same regardless of speed. Variable Torque is used almost exclusively on "quadratic" loads like centrifugal pumps and fans.
5. 2S1W / Dahlander motors must ALWAYS be started in low speed first, they are NOT built to be started them in High speed directly. If you need to be able to start in either speed, then you must use 2S2W. A 2S2W motor is always a larger frame size than the equivalent single speed motor of the same power rating, because it is essentially two separate motors in one housing.

More info in a clear manner on Dahlander motors.

http://www.lmphotonics.com/InductionMotor/dahlander_motor.php

Similar info on NEMA style 2S1W motors, you can see they are the same connections.

http://www.joliettech.com/3ph_motors_2_speed_single_winding.htm

Dear Mr Raef

Greatly appreciate the time you took to improve my understanding of two speed motors.

Jim Runciman

Deleted

Hi Everybody

I have a drilling machine which is operating normally now and this is what I can tell you about the journey.

We had an open circuit to one phase and that has been corrected. Motor is now quiet as a mouse.

We probably have a Dahlander winding which with a 5 position KM rotary switch give low and high speed in both directions. Low speed is activated before high speed.

Happy to have a successful outcome and appreciate the time taken by everyone to contribute to the problem identification.

Jim Runciman

Jim you also did it right.

1) You described the problem to the best of your knowledge.

2) You read the posted replies and acted upon them.

.....AND BEST OF ALL:-

3) You informed us of the final result........

Thanks Andy

Jim