Dishwasher Motors For Ebikes?

Discussion in 'Electric Bicycles' started by safe, Aug 11, 2009.

  1. safe

    safe Active Member

    Dishwasher Motors For Ebikes?

    First thing is to identify what the motor actually is. It has two wires and a ground wire. The coils are two in number and they wrap around an iron laminated core. I'm unable to see inside to look at the rotor, but my guess is that the rotor is a permanent magnet.

    Using RC motor terminology my guess is that this is a brushless "outrunner" motor. The size is about right for ebikes as can be seen in the photo.

    Now one can ask:

    "Why not just buy a high quality brushless RC motor and start there?"

    ...and my answer would be:

    "Yeah, that's probably true..."

    ---------------------

    I think it's interesting that these exist and can be gotten for free because of the large number of dishwashers in the world. Efficiency is likely not very good though, since it's running off of the grid.

    Why just two coils?

    Since it's designed to move water (which is heavy) you would think that it would need to have some pretty good low end torque.

    I wonder if something so simple and minimal could be used?

    (no brushes to wear out)
     

    Attached Files:

    Last edited: Aug 11, 2009

  2. rjs5700

    rjs5700 Member

    You might need a really really long extension cord.:jester:
     
  3. graucho

    graucho Active Member

    I have to rub the ol' forehead for a few moments on this one. Great theory. Ive only begun my journey of electric motors a few months back.
    I hope someone knowledgeable chimes in. You may have just scratched the surface within the appliance world. :detective:
    .
    .
     
    Last edited: Aug 11, 2009
  4. hurricane billy

    hurricane billy New Member

    sounds like a good idea if it works.hope someone knows
     
  5. johnrobholmes

    johnrobholmes Member

    It is most likely a universal motor. It would run on AC or DC. It would have brushes, and probably two field coils. The two power wires are hot and neutral, and then the third is a case ground.


    It would need a good rewind, for it is designed for 120v AC (rms) use. Starting torque is great on universal motor, but efficiency isn't great.
     
  6. SimpleSimon

    SimpleSimon Active Member

    My question is this: Given that the primary limiter of the utility of e-bikes is the power storage issue, why would you use a motor that is not as efficient as you can get?
     
  7. machiasmort

    machiasmort Active Member

    Simon presents a seriously valid point here. The wieghs out justify the means.

    A good idea would be to use that motor on a windmill! Never thought of a DW motor. Low RPM would probably work well to generate 110. I wouldn't know the first thing about regulating it tho.
     
  8. Esteban

    Esteban Active Member

    If looking for a cheap motor to adapt to a bike, the old car fan radiator motors were an early concept. Not that efficient, but the price is good. A few companies made these types years ago, but I don't know of anyone now. They were $$$$ when new. Look up; EV Warrior bike

    http://www.psnw.com/~jmrudholm/ebike.html
     
    Last edited: Aug 12, 2009
  9. safe

    safe Active Member

    There is no brush drag at all... it's completely free spinning... so it does appear to be a brushless motor.

    I tried connecting it to a 12V battery and it behaves like a brushless motor in that flicking the wires to the terminals can actually get the motor to move a little. (sort of like hand timing of the current pulses)

    Efficiency has two parts... there is "peak" (at a specific rpm) and "average" (across the entire powerband). It's hard to know what the efficiency might be just by guessing.

    Not all motors are alike... and my guess is that for something like a dishwasher the goal is to be able to get good low end torque and so while high rpm efficiency might not be ideal the overall power and efficiency might not be bad. I'm thinking it might be more like an induction motor or something. (I have no idea what the rotor is like)

    It's interesting no matter what... :idea:
     
    Last edited: Aug 12, 2009
  10. arceeguy

    arceeguy Active Member

    Most likely just an AC induction motor. A brushless DC motor would have at least three wires along with the frame connection, and a fairly sophisticated motor controller.

    I've seen some Electrolux/Frigidaire dishwashers that used permanent magnet DC motors for their pumps. Looked like a power wheels motor with a rectifier bridge built-in to convert the AC to DC. Thought it looked a bit cheap at first, but they run very quiet without the typical induction motor hum. You can hear a little bit of a whine from the brushes, but it was barely noticeable.
     
  11. safe

    safe Active Member

    That's what I thought it might be...

    The reason this seems so interesting is that the "Holy Grail" of electric motors for cars is an Induction motor. The Tesla uses an Induction motor. So here we have an essentially "free" motor (there are millions of dishwashers that fail for other reasons than the motor and are thrown away) and the size and weight appears to be right for an ebike.

    All that would be needed is a way to generate the 120 Volts AC that the system desires. If your ebike had 120 Volts of battery then all you would need is to design (or buy) a controller that converted the DC to AC. Here you might even be able to explore ideals like VARIABLE frequency AC as a way to increase performance. (some research into Tesla's Induction motor and controller would be useful)

    120 Volts is a little high for an ebike... but one cannot be certain that 120 volts is REQUIRED. Maybe with some tinkering you could invent some controller that ran on 72 Volts of AC and still get it to work right. Motors are not always directly tied to a specific voltage.

    It's an interesting thought... and Induction motors SOLVE the basic problem of ebikes in that they offer better low end torque which matter more than the top end. Ebikes are always starting and stopping and rarely run at the same rpm for long. And with multispeed gears it's even more interesting because it widens the powerband a great deal.

    If this all worked as a test case, then maybe down the road people start to build better ebike Induction motors for the actual products people buy. To my knowledge the Induction motor begins to make sense at about 1KW of power and that's right about where we want to be. (some desire 5KW of power of course)

    A lot to think about...
     
    Last edited: Aug 13, 2009
  12. safe

    safe Active Member

    SINGLE-PHASE INDUCTION MOTORS

    http://www.tpub.com/neets/book5/18d.htm

    There are probably more single-phase ac induction motors in use today than the total of all the other types put together.

    It is logical that the least expensive, lowest maintenance type of ac motor should be used most often. The single-phase ac induction motor fits that description.

    Unlike polyphase induction motors, the stator field in the single-phase motor does not rotate. Instead it simply alternates polarity between poles as the ac voltage changes polarity.

    Voltage is induced in the rotor as a result of magnetic induction, and a magnetic field is produced around the rotor. This field will always be in opposition to the stator field (Lenz's law applies). The interaction between the rotor and stator fields will not produce rotation, however. The interaction is shown by the double-ended arrow in figure 4-10, view A. Because this force is across the rotor and through the pole pieces, there is no rotary motion, just a push and/or pull along this line.

    Figure 4-10. - Rotor currents in a single-phase ac induction motor.


    [​IMG]

    My Comment:

    This appears to match my dishwasher motor...
     
  13. safe

    safe Active Member

    Pedal Start

    Most of the "tricky" control logic for single phase induction motors revolves around getting the thing started. Seems to me that you could build the thing so that the motor is directly attached to the chain (like on my bike now) so that you could in effect "kick start" the motor by pedaling into it. Once the motor is in motion you then can begin to apply an oscillating electric field on the two coils. The faster the oscillation the higher the motor wants to spin... so the control logic is really pretty simple.

    It's definitely attractive because for my own EBRR racing series concept I've wanted to have motors that are strictly limited to a 1K power input limit. With permanent magnet motors the peak efficiency occurs at a high rpm and when you are loading up the motor the efficiency is bad. With the induction motor, full throttle (but restricted by the 1K rule) will produce the best power and efficiency and the powerband becomes flat. (induction motors work their worse at no load speeds which are not needed for a racebike)

    Maybe the trick is to play with this motor a little? (this winter possibly)

    ...it makes my dishwasher leak damage seem to "make sense" in a cosmic sense because maybe it will get me to explore what might be the better future for ebikes. :cool:
     
    Last edited: Aug 13, 2009
  14. safe

    safe Active Member

    RC Brushless Motor

    There is not a lot of difference between the Induction motor and a brushless RC motor. They both work without brushes, so there's less to break, and they both require that the control logic has an AC quality to it, unlike the brushed motors that actually act as a simple voltage stream. (I know, PWM is not smooth, but conceptually it's more DC than AC)

    For my Electric Bicycle Road Racing concept the Induction motor makes the most sense because in a racing situation you are normally either wide open with the throttle or off with the throttle. Combine this with the fact that the Induction motor can be setup so that it's a "constant torque" device across the entire rpm powerband and you get very close to the ideal for a "Formula 1K Watt" racing league.

    If there is to be a type of racing that is designed with a strict power input limit then the Induction motor is clearly the answer and not the permanent magnet motors like the brushless RC motor.

    So I might just "leapfrog" past the intermediate step of the RC motors and go all the way to the Induction motor.

    Not sure at this point...

    All I know is that I don't really like the problems with commutators I've had. Maybe this is because of the cheap Unite motors I've been using, but the point is that Induction motors are REALLY cheap and if they can be made to be the superior motor for my racing concept, then that's probably a smarter way to go than the intermedate RC motor solution.

    The only difference is the core is a permanent magnet for the RC motor verses something solid in the case of the Induction motor.
     
  15. safe

    safe Active Member

    Three Phase Better Than Single Phase

    Dishwasher motors are Single Phase motors.

    Automobile Alternators are Three Phase.

    Go here for a great thread on Automobile Alternators being used as motors:

    http://www.rcgroups.com/forums/showthread.php?t=905411

    ...the alternator sounds like a better starting place once you break out of the confines of the brushed motor.
     
  16. safe

    safe Active Member

    Three Phase Dishwasher Motor?

    [​IMG]

    http://www.skdynamics.com/products/motors.htm#wash

    The first generation control for ACIM based washing machine was developed by SKD (1998-99) and is in production now by Frigidiare, USA. A total production of 460,000 units was made by Frigidiare, USA during the year 2000. The next generation control for this washing machine was also developed with additional features and lower cost. Over 1 Million machines have been sold in US market to date.

    ...so some of the dishwasher motors (better quality) use Three Phase Induction motors.
     
  17. safe

    safe Active Member

  18. safe

    safe Active Member

    Ebay Price - $88

    [​IMG]

    http://cgi.ebay.com/Frigidaire-Dish...0?hash=item518816e36e&_trksid=p3286.m20.l1116

    ...looking more closely it's a 1/3 hp motor, so pushing it to 1 hp will be heating it up a great deal. Hard to know if it can handle the heat. However, the size looks about right. (probably less than 8 lbs)

    Since induction motors can usually be overloaded a great deal (like a turbocharger) I think that you could try a 48 volt system using PWM to simulate an AC sine wave. Use VFD (variable frequency drive) and then limit the current so that you push the wires to the limit, but don't break them.

    The other option would be to rewind the motor with thicker wire.

    Looks to me like the pole count is pretty high... so that's good.
     
    Last edited: Aug 22, 2009
  19. arceeguy

    arceeguy Active Member

    Are you sure that replacement motor is a three phase motor? I realize that it has a bunch of wires coming out of it, but the label looks like it is just a single phase motor.

    I would imagine that if this was one of those three phase jobbies, there wouldn't be a RPM rating on the motor, as the three phase motor and controller is most likely variable speed. Otherwise, why would Frigidaire go through all that trouble just to have a motor spin at 3450 RPM when a single phase induction motor would do that without the sophisticated electronics.

    Here is the PMDC (brushed) technology used in my 2005 Frigidaire dishwasher. Yep, that's the same Johnson Electric that makes motors for toys and tools. But then again, some of those cordless drill motors are pretty husky!
     
  20. recumpence

    recumpence Member

    The motor you showed on the first page is from a GE/Hotpoint dishwasher. It is an AC induction motor.

    They really suck in quality, by the way. The newer motors are way better than those old style stamped steel pieces of garbage.

    Matt
     
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