Name this motor

Discussion in 'General Electronics Chat' started by #12, Jun 16, 2014.

  1. #12

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    It's labeled as 1050 RPM and 1/3 HP.
    It eats 240 VAC at 60 Hz. 2.8 Amp limit.
    It has 18 coils around the perimeter and 4 permanent magnets on the rotor.
    The driver is called, "constant torque".
    It lives where a PSC motor usually lives and drives a squirrel cage fan.
    What is the, "real" name for it?
     
  2. MaxHeadRoom

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    At first I thought it was a Fisher & Paykel Outrunner motor.
    But on closer look it appears to be a GE ECM, Electronically Commutated Motor, common now in HVAC systems, for RPM control.
    Google the ECM Textbook PDF
    Max.
     
    Last edited: Jun 16, 2014
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  3. #12

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    Does Brush Less Direct Current mean BLDC?

    or is it just an ECM motor?
     
  4. MaxHeadRoom

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    Yes, BLDC = Brushless D.C.
    I have never delved deeply into the ECM motor, or the Fisher & Paykel, come to that, I would like to know of a driver details?
    Probably proprietary?
    I usually work with BLDC and AC sinusoidal servo motors, which essentially are constructed identically, just the commutation is different.
    Both have a 3 winding stator with a P.M. rotor, as does the GE ECM.
    The Fisher & Paykel, used predominantly in washing machines use a wound inner stator, with a PM rotating outer, the very same principle as the R.C. guys use as Out-runners.
    These are also Brushless DC.
    Although constructed the same as the AC sinusoidal, the BLDC is described as such because it is likened to a DC brush motor turned inside out, only two windings are energized at any one time.
    With the AC sinusoidal, all three windings are fed with a 3 phase signal.
    Both considered synchronous motors.
    Max.





    .
     
  5. #12

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    I assume you are asking me for details about THIS motor.

    This motor driver has a sensor mounted inside a toroidal inductor. It probably is about measuring current. The windings seem to be 3 phase because the 3 wires coming out of the mess of coils are all 22 ohms across any 2 conductors. In my mind, it is a 3 phase stepper motor. It is harnessed to a squirrel cage fan that is way too big to run at the labeled 1050 RPM with only 1/3 of a HP. The result is that the motor runs rather slowly, like 400 to 450 RPM. Very good for high efficiency and low noise levels. If they could only get their MTBF higher than 5 years and their price below $400, it would be an improvement over a PSC motor.

    Page 12, X13 Constant Torque ECM in the ECM textbook.

    The use of constant torque should make this motor bulletproof because it would be impossible to overload it. Besides that the RPM has almost no relationship to the number of coils. It can run at 50 RPM or 500 RPM and the only thing that changes the RPM is the load.

    The driver is programmable by each OEM, and they do. They have accomplished making this motor un-repairable and un-substitutable, unless you can come up with a complete blower housing that will fit the hole it's supposed to blow air into.

    See this thread, post #21
    http://forum.allaboutcircuits.com/showthread.php?t=98405

    Any more questions?
     
  6. MaxHeadRoom

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    It was a rhetorical question, I didn't expect and answer, although if you find one i will take it.:cool:
    It is definitely not a stepper motor, it is either commutated as BLDC or AC sinusoidal.
    The typical BLDC motor has 3 Hall sensors or equivalent for commutation spaced at once every 120° per electrical 360 degrees.
    e.g. 8 pole = 4 electrical rotations per mechanical rotations.

    It would also be nice to see details of a driver for the Fisher & Paykel motor which is rather interesting!
    Max.
     
  7. shortbus

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  8. #12

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    No sensors in the winding area and the motor section is more than an inch from anything on the circuit board. I don't see any optical coupling or magnetic sensors. All 3 connections being the same resistance from each other tells me there is no start winding.

    Turning the rotor by hand feels like a stepper motor in that it has preferred resting places. The RPM being entirely dependent on the load suggests a variable frequency drive. The description on the genteq website says it is a constant torque design and goes into detail about how, as the air filter gets dirty and the air supply becomes restricted, the motor increases RPM because being starved of air reduces the load on the fan blades. Reduced load means increased RPM at the same torque.

    The marking on the driver chip is: IRAMS1 0UP60A

    My biggest problem is a severe lack of education about motors.

    Here's the driver:
     
  9. THE_RB

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    If it has no sensors it probably uses BEMF sensing to control commutation.

    Why is it "unrepairable"? The coils will be extremely reliable so failure is likely in the electronics. And if they commonly fail there is probably a common failure point, so once you diagnose and repair one motor the other motors will be very easy to fix.

    It's probably as simple as replacing that large vertically mounted IC, or dried out electros close to it.
     
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  10. MaxHeadRoom

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    It is pretty certain the GE ECM motor see the PDF.
    Max.
     
  11. inwo

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    Wonder the same thing.

    Have you looked at the input circuit and any protection devices it may have?

    Fuse, open trace, mov, current limit, rectifiers?

    If it's surge damage look around where green wires connect!

    Even if it took a month to fix. It may be worth the effort in the future.
     
    Last edited: Jun 16, 2014
  12. MaxHeadRoom

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    The GE ECM literature name it as a BLDC 3ph P.M. motor.
    Also mentions that it is normal to see a slight rock back and forth of the rotor when first powered in order to establish the stator/rotor relative positions, for sensorless commutation, as is sometimes seen in BLDC servo drives where the commutation devices are not present and the encoder is used after the initial recognition by the Dsp controller.
    Programming options for the ECM 2.3 include: rotation direction, start/
    stop ramp rates, on/off blower delays and many other functions––all stored in the motor’s microprocessor. Even its speed and torque characteristics can be customized to meet specific performance
    requirements.
    Max.
     
  13. shortbus

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    The reason I said it is a PMAC motor is that it doesn't seem to have the rectifier section that is required for a BLDC motor.
     
  14. shortbus

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    I've seen this statement in a couple of threads. The Fisher & Paykel motors are "inrunner" not "outrunner" motors. The F&P motors have a PM rotor on the inside with a stator surrounding it. Outrunners have the rotor on the outside with the stator on the inside.
     
  15. MaxHeadRoom

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    This is the F&P PDF on the motor.
    It shows a 36 coil inner stator that has three stake on connections, No slip rings, therefore cannot rotate.
    The outer rotor carries the magnetic poles, inner stationary, outer rotates.
    https://www.youtube.com/watch?v=_P027KQ8ZHo
    In the utube video the guy shows it running but he calls the fixed inner coils the rotor, for some reason?
    My RC outrunner motors I have are identical in construction principle.
    Max.
     
    Last edited: Jun 17, 2014
  16. #12

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    The circuit board is flooded with a gray foam, on top and underneath. No known solvents, won't melt even with liquid solder touching it, can't get the board loose without breaking it. It took me 5&1/2 hours to dig most of the foam off the board, and 2 SMT resistors came loose. That is why I consider it unrepairable. I would love to be able to replace the driver chip. That would save a few hundred dollars.

    Meanwhile, I am on a borrowed computer and find this activity very inconvenient. Signing off until I get home..
     
  17. MaxHeadRoom

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    I have noticed others on sites that have had a similar problem when trying to repair, so far I haven's seen anyone that has been successful.
    Max.
     
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  18. THE_RB

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    Ahh, that makes it a pain. However, now you have access I would check those small electros (assuming you have access to the bottom of the PCB for soldering). If it as simple as a dried out electro, that is always in the same place, you can just dig out the foam in that one place to fix future motors.

    There was a VCR in the early 90's with an expensive capstan motor ($90?)that always failed in the field. I discovered a 10uF electro on it was dried out, so all that was needed on future motors was to replace that cheap electro. I must have done 20 of them or more after that, for a nice profit.
     
  19. inwo

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    Same experience with satellite receivers in the 80s.

    Once the problem was found for a certain model, the same part would almost always fix others.
     
  20. #12

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    I don't have access to the bottom. The board is foamed into the aluminum end plate of the motor. I might be able to use feeler gauges to break up the foam under the board, but it doesn't seem likely that I can get the board out without breaking it. (See photos in post #1 and post #5.) Also, the foam is not brittle. It is a flexible, rubber like foam. Very stretchy and medium tough.

    I have pretty much decided that I will not be rescuing circuit boards to save my customers from the $500 Trane blower motor. The point of this discussion was about learning if there is any way to, "fake" it. The answer is, "no". You can't just install a PSC motor because the squirrel cage is so big that a third of a horsepower would have to run somewhere in the range of 400 RPM to 450 RPM. Only a complete blower housing with a much smaller squirrel cage would make this work, and you're back to several hundred dollars at the wholesale level.

    If I owned this air conditioner, I would try to change the whole blower assembly, but I'm not going to try to redesign it for my customers. Now I know why I'm not going to do it.

    Thank you for helping me understand why this design is pretty much un-defeatable.
     
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