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Motor Identification 1

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Colt1911

Computer
Sep 29, 2010
10
Need help in determining what type of motor I have. I have an idea, but want some input from someone more learned than myself. The reason I need to know is because I intend to attach a motor speed control, and some of the information I have is in conflict.

The facts:

The product is Master Flow PG1 Gable Vent (it is not the newer models nor does it use the newer replacement motor listed on their website)

Label information:
DM (Asia) limited
model#:DOW-136-0-34-XIN
UL (listing#) E193815
1050RPM

6 poles are clearly visible from the back of the motor, so I'm guessing brushless AC induction.

My conflicting information is:

1 HP=746w (%100 efficiency)
The label states 3.4 amp. I tested the motor at 3.4 amp.
My math: (V=IE) 120*3.4=408w
746/408=1.8HP

The label states 1/13HP ?!?! (misprint?? 1/3??)

Question:

1. Is there a definitatve way to determine the type of motor? (ie brushless/brushed) (AC/DC)

2. Where have I gone wrong in my calculation of the power/HP of the motor

3. What type of speed controller will I need? (frequency/pwm/rheostat?)

4. If I need to build a circuit for cost effectiveness, any good links to what I might need?

Thanks
Colt
 
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picture of the motor label at the bottom of my first post
 
408 VA not 408 watts. You forgot about efficiency and power factor.

If it doesn't have speed control now, I'd assume it is an induction motor, so you're probably SOL in regards to a simple way to adjust the speed.

Maybe time for a new plan/project.





David Castor
 
Thanks for the reply.

just noticed I wrote the formula wrong. P=IE. And correct me, please, if I'm wrong but 120V*3.4A yields 408watts. 1HP is equal to 746 watts. 746 divided by 408 is around 1.8. I doubt pf & eff will lower it to 1/13th HP which is around 57 watts. I have already metered the motor at 3.4A, and AC motor (if it is in fact) are qute efficient. Begging your pardon, but could you explain your V/A answer?

How can efficiency and power factor be calculated without first detemining the type of motor?

I would never assume becuse someonthing lacked a certain control that it was a device of a certain type. The device is designed to run full speed or be off, controlled by a tstat.

My soulition doesnt need to be simple, just cost effective ie if an expensive controller is required, I can build one rather than a OTS soulition.

My primary concern is motor ID. I see no reason to change any plans at this point.
 
120V*3.4A yields 408watts

This is seriously incorrect for ac circuits, unless the power factor is unity, which it won't be for this motor.

For ac circuits P = V*I*pf where pf = power factor which is the cosine of the phase angle between the current and voltage.

In addition the 1/13 hp is the motor OUTPUT power. You are trying to calculate the motor INPUT power. So the difference is the motor efficiency, which is probably horrendous for this little motor.

You can assume or not assume whatever you want. I'm just trying to offer practical advice. Feel free to purchase an adjustable frequency drive or build one from scratch, if you desire. As for cost effective - very doubtful.

Good luck.



 
I havent in fact been able to determine if this is in fact an AC circuit. Hence the hedging on the power factor etc.

The output vs the input power would explain the descrepancy, and if your correct would be horrendous!!

I appreciate your advice, and your time to give it. Assumptions are something I shy away from in general, and in this case could damage equipment, or worse, pose a safety hazzard.

I still await motor identification to determin if an OTS, or custom soulition is preferred. As for cost I keep bins, and bins of junk electronics for just these type of project.

Thanks for your input.

I am looking to ID THIS MOTOR, as to its design type (AC/DC/brushless/brushed)

Thanks
Colt
 
It looks more like a 1/13hp motor and not 1/3hp. Try 408/746*effiiency*powerfactor (not 746/408). And as dcp said the power factor will make a big difference.
 
thanks for the reply

never said it was 1/3HP, speculated 1/13 could be misprinted given that it is 3.4A @ 120V.

Sadly no one seems to focus on the main question 'what TYPE of motor is this' Which is what I REALLY need to know.

I may well end up tearing it down.

surly I can find all the formulas online I need when that has been determined. Until then, power factor and efficiency are useless and meaningless.

It could be a brushless DC MOTOR!!!

Thanks
Colt
 
Colt, since you've looked inside the motor, you have more information than all of us put together.

Let's see here! No commutator so its not DC and its not a universal AC motor.

Check the rotor for magnetism. If it's not magnetized, its not brushless DC, stepper, or AC.

That pretty much leaves AC induction. Count the power wires going into the motor. If there are only two, its single phase AC. If three, it's three phase AC.

Based on what's already been posted, its likely a single phase six pole AC induction motor.

As was already pointed out, you are figuring hp upside down. It's 408/746 = about .55 assuming perfect efficiency and power factor which will not be.

Given an induction motor, on 60hz power, the motor will turn 1200rpm at no-load and 1050rpm at full load. Speed loss is about linear as load changes between those two points.

Has this helped? What more do you need?
 
actually I havent torn the motor down YET. I was REALLY hoping to avoid that since its a pain, but with no other suggestions I guess thats on my todo list tomorrow.

Honestly, 'assumed', and 'likely' just dont cut it. I was hoping the learned scholars on this 'electric motor forum' would have an easy way of testing. Since its already been built into a duct system, and teraing it out, tearing it down, then reassembling the entire thing will take several hours for what will seem a pitance, yet pinnacle bit of information.

I cannot procede forward with any type of motor control, be it built or bought, without knowing the properties of the device to be controlled. In the original plans there was no speed control, so the device was installed. Now it seems I will have to tear the entire device down to glean one tidbit of information. I only want to do this once, so it must be right the first time.

Thank you for pointing out I had the formula backward, though irrelevant since after I figure out the motor type I will run the numbers 20 times 7 different ways before I buy/build.

I was just trying to get a quick answer, and maybe there is none. I sincerely thank everyone for their time, effort, and suggestion. I havent meant to cause any problems.

If you have any other thoughts on an easy way to determine the SPECIFIC TYPE OF MOTOR this is ie. electrical test/circuit test, I would be more than welcome to have them.

Thanks
Colt

 
Colt1911 said:
Sadly no one seems to focus on the main question 'what TYPE of motor is this' Which is what I REALLY need to know.

Unfortuantely, you did not type in all the information on the motor faceplate, in your first post. In fact you left out the bits that actually answer your question!

The faceplate clearly says, it is a single phase, 60 Hz, 120 Volt, 3.4 Amp motor.

Actually, it is a common fan motor, "shaded pole" type. Offcourse, it has very low efficiency and pf.

What type of speed controller will I need? (frequency/pwm/rheostat?)

In the original plans there was no speed control, so the device was installed.

You do not control its speed with VFD or PWM chopper. A rheostat or a dimmer would do. Energy efficiency of the motor+controller will go even lower.

 
I'll go with shaded pole also. Look for a heavy copper or brass loop around a part of each pole face. Expect a poor power factor and lots of heating losses.
Let us know how the speed control works for you.

Bill
--------------------
"Why not the best?"
Jimmy Carter
 
This is definitely a shaded pole motor. 1050 RPM is a typical speed rating for a 6 pole shaded pole motor. And it is not uncommon to see efficiencies below 20% on a shaded pole motor, which would explain the 1/13HP output power.
 
@ RajeevCell

I posted a pic of the label in my first post. Unfortunately, its just a teeny tiny link at the bottom which is why my second post, right under it was to bring attention that the link existed.

I am not familiar with 'shaded pole' design, and this gives me something to research, and see if the facts support the evidence.

I am truly suprised that modern motors such as these would have efficiency below %20!! If true, now it might be time to consider a new plan!! Maybe I coud rip the motor add a pully, and use a belt drive system with a different external motor? We'll see.

Thanks for all the input.
Colt
 
Yeah, efficiency is horrible on shaded pole motors but they are still used because the initial cost is cheap.
 
read a brief description of theory on the 'shaded pole' design. Makes more sense to me now why they are so inefficient since they only use about half the wave. that would probably always put them under the %50 mark for efficiency. This fan would cost me about $20 a month, just to run at full speed, and slowing wont save any money (which wasnt the reason for the speed control), in any case, that just wont work fo me. I need an air mover.

Colt

 
I want to thank everyone who took the time to help me with my problem.

Thanks a million, you guys are great.

Colt
 
This motor is a 1/7 HP according to the replacement motor listing in the product manual.

I understand why you might want to slow it down as I have heard one of these things running before, only once, and it was in my house. I took the cord of the thing it was so loud.
 
 http://www.gaf.com/Roofing/Residential-Roofing/Roofing-Products/Attic-Vents-Roof-Ventilation/MasterFlow-Power-Gable-Vent/Documents/MasterFlowPowerGableVentilatorsExhaust-03-WarrantyInformation-257-67-5422.pdf
The issue on the nameplate HP being so low is that (as was said earlier) this is the mechanical output (shaft) power rating, not the electrical power consumption. The electrical power consumption is given to you in the Amps and Volts from which you can determine VA requirements for the supply circuit. But because a Shaded Pole motor has so little torque, it's conversion of electrical power to mechanical output is horrendous.

Cheap, small, efficient; pick 2.

You can change the speed of a SP motor by simple voltage reduction. Well actually you can change the TORQUE by voltage reduction which will indirectly change the speed. They are "impedance protected" motors so they will not burn up. But changing the speed that way will not actually save energy significantly, if that was your goal. If you just want speed control, go to the hardware store and by a ceiling fan speed controller, it's a dimmer that is a triac with a snubber circuit. Should cost you around $10US.


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