Snub has more Electric Motor Questions:

[snub]

I have a surplus motor that I am using for my magnetic tumbler project. It is 120 VAC, 3 speed motor (1575, 1400 and 1250 RPM according to the tag on the motor.) Here is my 'rendition' of the motor tag:




       



I only had a 'single pole- double throw' switch to experiment with, so I just used the high and low speeds. Problem is, the motor only runs at one speed, regardless of the switch position. This is according to my digital non contact tachometer. Even with the switch out of the circuit, it doesn't matter if I hook up the black, blue or red wire to the second line in wire, it still runs at a single speed, which is 1720 RPM.  Which doesn't coincide with the rated fastest RPM of this motor. Strange thing is, I have another project with a 3 speed motor, and it does the same thing. Will only run at a single RPM. Also, when you switch between high and low speeds, the 'sound' of the motor changes, but the RPM doesn't. Here is how I wired it:







I'm wondering if that brown wire needs to go somewhere else, besides ending at one terminal of the capacitor?

[Bluechip]

Hi Snub

Your 1720 RPM is right for a 60Hz motor with 2 pairs of poles.

What you may have is a motor designed to run via an external control circuit.

ie under a system known as Pole Amplitude Modulation (PAM)

.... and you don't have that!

Dunno how much you know about Induction motors but the general rule for rotational speed (sychronous) is :

Numbers of cycles per MINUTE / Number of pairs of poles

So, for 60 Hz you get 3600/1=3600  3600/2 = 1800  3600/3 = 1200 etc.

Less a bit for the slip you get  3450, 1725, 1150, etc. which is what you see on the Rating Plate
These are the more common numbers for 60 Hz motors.

By way of the switching some of the windings you get wider or narrower pole widths, effecively varying the number of poles.
The result of this is  the motor speeds do not appear to correspond to the usual equation.
Instead of the sychronous speed following the equation each time, you get a set of speeds grouped together, as you seem to have
Tried to understand this stuff years ago, it's gruesome ..

You get this arrangment on desk fans, spin dryers etc.

I think you should get another motor  

Try a search on the motor maker/type. See if any info.

Can't really help from here, but I can admire your problem  

Dave BC


 

[John Hill]

I do not know anything about this particular motor but by looking at your diagram we can see there are not too many possibilities.

We will assume that the white/brown/capacitor network is common to all speeds so what we have left is three wires,  you have already tried connecting to these wires individually and the speed does not change, but the sound does.

Dave has told us these motors operate by interaction of multiple run windings so it is logical that with just one run winding connected, no matter which one, the speed will be the synchronous speed, which you have shown it is.

I think the only options left are to connect  black-blue,  blue-red, and red-black in turn  and see if that gets you the three speeds.

John

[Bluechip]

Hi Troops

Assuming that's what the motor IS !!

Could be        

What is it off anyway?  Could be a clue if known.

Still reckon it's a better idea to find a tame one ....

Dave BC

[kwackers]

I don't know an awful lot about motors - but I'd *imagine*...

If the motor works by switching in varying amounts of poles - then presumably if you apply 'live' to say the red wire and get 1720rpm, the I'd think if you leave that connected and also apply power to another (say blue) then this would 'create' more poles?
So instead of switching the wires you simply connect more of them. Of course it could also be that the wires need connecting to neutral...

However, I'd start by measuring resistance between all wires to give myself some idea of how it's wired internally first.

[John Hill]

Hi Troops

Assuming that's what the motor IS !!

Could be        

Unlikely Dave,  Snub has already determined that nothing untoward happens when connecting to each of those three wired individually,  connecting two together would be putting two in parrell.

Incidently, when playing with motors or transformers it is well to recognise that inductance plays as big a part as resistance and inductance is harder to usefully measure.  I use a light socket in my test rig with the socket wired in series with the device being tested,  if the light glows to full brilliance I know that is a very low reactance connection or a short circuit, very useful to avoid smoke escaping suddenly.

[John Hill]

I don't know an awful lot about motors - but I'd *imagine*...

If the motor works by switching in varying amounts of poles - then presumably if you apply 'live' to say the red wire and get 1720rpm, the I'd think if you leave that connected and also apply power to another (say blue) then this would 'create' more poles?
So instead of switching the wires you simply connect more of them.

  Exactly, you have explained it better than I did.

Of course it could also be that the wires need connecting to neutral...

The information from the name plate does not even hint at that. 

However, I'd start by measuring resistance between all wires to give myself some idea of how it's wired internally first.

  This is a motor, all coils will be quite low resistance.  Besides, we already know from Snub's tests that there is a circuit from the white or brown wire to each of the other three.

[snub]

So many smart people on this forum, that's why I love it. I would like to continue pursuing my problem, even if only to learn more about AC motors.

The Motor is a Welling, model # YSK60-4E. I searched hard but couldn't find anything on this particular model. I did, however, find some info on model # YSK60-4C.  I am 'assuming' they are similar, but obviously not the same. The YSK60-4C was used as a fan motor in a York air conditioning unit. I managed to score this wiring diagram from the Interweb:





It appears as if there are some resistors inside the motor, and looking at the diagram, I would say that the theory of joining different wires together for the different speeds has a lot of merit.  I'm wondering why this wouldn't appear on the motor tag. I am looking forward to all your comments!


P.S. I did a screen cap of this PDF diagram to get the pic. I see that it's not very clear. If anyone wants, I can clean up the important parts.

[John Hill]

Those things inside the motor are coils and the other little gizmo is the starting switch.


We can ignore column 'A' of the switch diagram as that controls the louvre motor and we can ignore everything below the 'Off' line.  So it looks like the three wires are connected to one line for each of the three speeds and they are not connected together.  I suspect the problem is with the connections to the brown and white wires in your original diagram.

John

[snub]

Coils, not resistors? The only knowledge I have of coils are the automotive type, that increase voltage. I was looking at how the yellow and white wires seem to end at ¼ and ¾ of the coil. And the red wire ends at the beginning of another coil. Obviously, I should have not have dropped out of school when I was sixteen and become a truck driver. But I'm not too old old to learn. Thankyou for your help!

[John Hill]

Well just be careful!  It doesnt matter if you pop the circuit breaker or even let the smoke out of the motor  but we do need you around to come back here and report progress!

The seperate coil connected to the red wire is the starter coil, that little switch opens when the motor gets up to speed so this coil is only used for starting.

Of course the wires in that diagram are not the same colours as those in your motor!

[DMIOM]

Coils, not resistors? The only knowledge I have of coils are the automotive type, that increase voltage. I was looking at how the yellow and white wires seem to end at ¼ and ¾ of the coil. And the red wire ends at the beginning of another coil. .........

well - the diagram you've captured does use the electrical coil symbol (which is a 'curly' line, like an over-extended spring, whereas a resistor is a zig-zag) but in fact they're not coils on their own - they've used that symbology for the windings in the motor - so the wires are tapped in to various points in the motor windings .....

As John says, the separate winding is, I think, the start winding and the symbol above it (can't read it clearly) will be the CFS (centrifugal switch) which disconnects the start winding when the motor gets up to speed.

Dave

[Bluechip]

Hi Folks

Can't see it too well either, but ..

It looks like the symbol for a thermal trip to protect the windings ..

Usually looks 'castellated' , like a square wave .. or the top of a castle ....  

Some in here if you want to trawl down far enough, although many manufacturers have their own 'version' of the standard (?) symbol.

http://www.wiringmanual.com/norm006.html

Can't be a centrifugal switch for starting, it would be in series with the capacitor. Or at least in a series 'winding / switch / capacitor' circuit.
Usually doesn't matter which sequence they are in.
Many FHP motors that are not required to start up against any great load, ie fans etc. are capacitor run motors wherby the cap. is permanently in circuit.
Which is almost certainly the case here.

EDIT Sorry, jargon slip ... FHP is 'Fractional Horse Power' 

Dave BC

[John Hill]

Can't be a centrifugal switch for starting, it would be in series with the capacitor.

That would certainly be true if the capacitor was used for starting only but in this diagram the multi-tapped coil is in series with a capacitor which must be always in the circuit. 

A starting circuit must produce a phase difference between the run coils and the starter coil, this is often (usually?) done by adding a capacitor to the start coil which has the desired effect of changing the phase of the start coil in relation to the run coils.  However, in this case, where the presumed start coil does not have a capacitor but the run coil does there is still a phase difference and hence an effective starting effect.

Many FHP motors that are not required to start up against any great load, ie fans etc. are capacitor run motors wherby the cap. is permanently in circuit.
Which is almost certainly the case here.

Agreed, the capacitor is permamently in the circuit.  The differences are that this motor appears to have a seperate starting coil and of course the tapped run coil for the speed steps.


Otherwise that would seem to be an odd place for a motor protection device as even with that component open circuit there would still be power on the tapped coil.

[Bluechip]

John

Yes, struck me as being a curious arrangement.

But it does look like a thermal device of some sort. And it would be reasonable to have one.

Pity it ain't on the bench .. would be fairly easy to sort out from the daig.. 

Dave BC

[75Plus]

I am wondering how the motor starts in Low and Med speeds if the coil attached to what appears to be a thermal switch is only in the circuit for High speed. One would think the slower speeds would need more help to start.

The color scheme is also not what you would expect on this side of the pond. White is almost always neutral.

Joe

[DMIOM]

I am wondering how the motor starts in Low and Med speeds if the coil attached to what appears to be a thermal switch is only in the circuit for High speed......

With respect Joe, I don't think thats exactly the case.   

That aircon diagram shows the extra winding with the CFS or thermal switch as getting direct power when in high speed mode - but there's also a connection between the "left" end of the smaller winding and the "left" end of the multi-tapped winding; so whenever any of the red, yellow or white are energised, the small winding will have power applied to it - albeit via varying amounts of inductance.   And ... as the switch probably forces you to go from off via slow and medium before you get to fast, the extra inductance "to the left" of the white tap, before it connects to the end of the smaller, supposed start, winding may help act in lieu of the start capacitor ......

Dave

[John Hill]

I am wondering how the motor starts in Low and Med speeds if the coil attached to what appears to be a thermal switch is only in the circuit for High speed. One would think the slower speeds would need more help to start.

I think the switch is open at high speed and that single coil is only used at starting.

The color scheme is also not what you would expect on this side of the pond. White is almost always neutral.

Joe

Brown phase, blue neutral and green/yellow ground is what we have in this part of the world.

I do not think the colours in the diagram can be taken as any sort of indication for the motor that Snub has.

John

[John Hill]

I am wondering how the motor starts in Low and Med speeds if the coil attached to what appears to be a thermal switch is only in the circuit for High speed......

With respect Joe, I don't think thats exactly the case.   

That aircon diagram shows the extra winding with the CFS or thermal switch as getting direct power when in high speed mode - but there's also a connection between the "left" end of the smaller winding and the "left" end of the multi-tapped winding; so whenever any of the red, yellow or white are energised, the small winding will have power applied to it - albeit via varying amounts of inductance.   And ... as the switch probably forces you to go from off via slow and medium before you get to fast, the extra inductance "to the left" of the white tap, before it connects to the end of the smaller, supposed start, winding may help act in lieu of the start capacitor ......

Dave

The way I read it, if low speed is selected only the end of the tapped coil is in series with the capacitor and all the other coils are in series and connected to neutral.  When the motor speeds up the switch opens leaving the motor to run on just the single portion of the tapped coil.

John

[snub]

Thanks for all the input.  As I mentioned at the beginning I have another 3 speed motor that will only run at one. It is an A.O. Smith. I tried searching with the model number but got nowhere. But, I did find this short technical article on their website with some good information about multi speed motors. Unfortunately, I'm not able to understand it completely. Perhaps someone could simplify it for me.


"Multi-speed motors come in two basic varieties. The first variety has an extra set of windings called a booster winding that behaves like a transformer. The second variety comes with two distinct separate sets of windings.

So how do these motors work? Remember from last issue how you determine motor speed by the number of poles (poles divided by the constant 7,200 gives you revolutions per minute). When the motor is under load, however, the rotating part of the motor slows down or “slips.”

If the load is constant, you can increase the slip by weakening the strength of the spinning magnetic field. One way is to decrease the voltage to the magnet wire that makes up the poles.

You can decrease the voltage externally by using a speed control or internally through the use of the booster winding in a multi-speed motor. In other words, the booster winding acts like a transformer, changing incoming line voltage to a lower voltage at the windings.

The booster winding may come with taps that allow you to apply different voltages to the poles, creating different speeds in the motor. Remember that “speed” taps just affect the strength of the spinning field—not the actual speed—meaning you can only affect motor speed with a load on the shaft. This is because slip occurs when the load works against the weakened magnetic field. Consequently, if you bench test a multi-speed tapped motor using a tachometer or strobe, you will detect little variation between speed taps since there’s no load.

Since the booster winding method of creating multiple speeds involves using a motor with just a single set of pole windings, you’ll find that the horsepower is always lower as the speed (voltage) is reduced. Consequently, this design is generally unsuitable for loads other than fans.

The second type of multi-speed motor with two completely separate sets of windings allows you to use one or the other speed at a given time. Having two pole sets wound independently offers you more flexibility to produce constant horsepower in mechanical applications since you are energizing just one set of poles at a time.

We also refer to a multi-speed motor “weakened” by speed taps as a multi-horsepower motor. For example, if you have a 1/3 horsepower three-speed motor, it generally would deliver 1/3 horsepower when connected to its high-speed tap, ¼ horsepower at its middle-speed tap, and 1/6 horsepower on low speed.

Knowing this, you can begin to appreciate the versatility of multi-speed motors in the field. You could use the above multi-speed motor to replace single-speed 1/3 horsepower, ¼ horsepower, or 1/6 horsepower motors with the same number of poles. To achieve the correct results, simply select the correct tap and carefully insulate the two unused taps. The result would be a motor that produces the same performance, similar fan noise characteristics, and the same static pressure as the original single-speed model.

Multi-speed motors give the service technician another versatile tool in the field. That's why is always good to have some in stock for emergency substitutions."