Dishwasher Motors For Ebikes?

[safe]

The motor you showed on the first page...
The newer motors are way better than those old style stamped steel pieces of garbage.

It did get me to thinking about actual Induction motors being used for ebikes even if those older ones are of low quality.

The main point (for me) is the shape of the powerband and not so much peak power or peak efficiency. I know I'm off in a sort of weird direction with this obsession about a racing class that is given an input power restriction of 1000 watts, but once you get past the concept and once you agree that the "game" would be to translate the 1000 watts into the widest powerband possible, then the Induction motor makes sense.

I wonder if there is a company out there that makes specialized small Induction motor of really high quality for something like the military or NASA. They might not advertise what they make, but just getting a look at what the best professional minds can come up with would be educational.

If anyone knows of the existence of high quality small and lightweight Induction motors that put out about 750 watts of power please post something about it.

Recumpence, what is your opinion of Inductance motors being used on ebikes? They could be nearly identical to RC brushless motors with the only exception that the rotor creates it's own "turbocharger like" feedback for it's magnetism verses the fixed magnetism of the permanent magnet motors. Efficiency is then based on being at full throttle and not rpm. (a big difference)

What about trying to hook up an RC system (ESC) to one of these Three Phase Frigidaire motors?

It would work wouldn't it?

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Alternatively...

What if you took a RC brushless motor apart and replaced the permanent magnets in the rotor with a squirrel cage Induction type rotor? Then you could see what it felt like as a difference.

Maybe the secret to the ebike Induction motor is to start with an RC motor and modify it?

http://en.wikipedia.org/wiki/Induction_motor

 

[recumpence]

The ESC would not recognise the motor because there is no permanent magnet to give a Back EMF signal. That is the problem.

I degauzed two RC motors in a top speed RC car (I pulled HUGE power out of each motor untill the magnets went). When that happened, the RPM went through the roof! One motor registered way over 100,000 RPM when the arm degauzed. However, once the throttle let off, the motor would not restart because of no back EMF. The innitial crazy high RPM was caused by no back EMF going to the controller (or a decreasing back EMF) causing the ESC to hunt for a signal and give progressively higher and higher RPM.

It was interesting!

Matt

 

[safe]

No BackEMF

Ahhh, yes... that's right... the ESC relies on a backEMF to function.

The Induction motor does produce a magnetic field in the rotor, but it's offset by the amount of "slip" that is taking place. (so no matter what the "slip" will confuse the ESC) My guess is that the better way to go is to use something like a tachometer and then integrate that with the controller. Permanent magnets don't have the same "slip" taking place.

The fact of the matter is that an Induction motor for ebikes doesn't appear to be an easy thing to do, however, it does look to be the right thing to do in the long run because full load operation is what is desired in a racing ebike configuration. (not the high rpm no load stuff that permanent magnets are good at)

This winter I might try getting some kind of Three Phase motor and some MOSFETS, a PIC, a tachometer sensor and a current sensor and see if I can put together something to play with next year. (even better would be to buy something that already does this)

What is needed:

48 volt DC (input)
Motor Rewinding (to optimize performance at 48 volts)
Variable Frequency Drive (VFD)
Torque Control (exactly 1000 watts of input power is allowed across the entire powerband)

My hope is to get a new workspace built in my house during this remodeling/repairing process this fall so I will actually have someplace to work in the winter. It's hard to squeeze everything in during the summer because I just have too many things to do with the house.

Never buy more house than you need unless you can afford to pay for servants to take care of it all. In the end the bigger the house, the less free you are for other things. (the big house ends up owning you)

This year I got three solid months of ebike work... something like 3-4 blown brushed DC motors (rewinds), a bunch of fiberglass work, a blown 8 Speed Sturmey Archer rear hub and only about 200 miles of actual road time. But I did set a new downhill record for my bike at 60 mph, so it wasn't a completely lost season.

 

[safe]

Actual Motor Purchased

I bought it for $25 on ebay.

I'm staying true to my convictions of creating a flat powerband 1000 watt motor and while I'd like to go all the way to the ideal of the Switched Reluctance motor this Induction Motor is going to be the in between step that gets me closer to that goal. Induction motors are easier to control and so that makes getting it to work easier.

Since these motors are designed for a higher voltage they will come with many turns of thin wire. This means I'll be rewinding it with fewer turns of thicker wire so that I can get it to run at 48 volts.

The size looks about right.

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I know I'm taking a "divergent turn" because the masses seem to want to go in the "Big Power" direction, but that's always been counter to my philosophy on these projects (since the beginning really) so I'm focusing on high quality and flat power verses increasing it in sheer volume.

I march to the sound of my own drum...

 

[safe]

The Programmable Controller

http://digikey.com/scripts/DkSearch/dksus.dll?Detail&name=497-4731-ND

$47

http://www.st.com/stonline/books/pdf/docs/11177.pdf

(seriously.... you ought to check out the pdf)

I'm not totally sure, but this looks very interesting...

 

[safe]

Going For A Low Cost Start

While the programmable "Evaluation Boards" look nice, they don't actually come with their own power boards and those boards tack on another $100 or more. Still a good price overall compared to buying a Curtis controller or something like it, ($1000) but you can live with less functionality. (the "Evaluation Board" has a Windows interface to play with)

The bare necessity is to have a CUSTOM microchip that can control the AC PWM switches that drive the MOSFET's or IGBT's depending on what voltage you are using. At 48 volts the answer is to use MOSFET's and I already have a bunch from my older controllers. I stress the word "custom" because if you start with a generic PIC then you have to implement the Three Phase math code which is an unnecessary exercise.

And I can recycle my old MOSFET's for the power...

The only thing I need then is the control chip and you can use these that only cost $8:

http://digikey.com/scripts/DkSearch/dksus.dll?Detail&name=MC3PHACVPE-ND

Combining the price of the motor and the chip I'm still under fifty bucks.

The overall design can be simplified to this diagram: (click below)

 

[spad4me]

This looks like a do able project.
Similar to your triple wound high performance DC motors.
I like the idea of a three phase motor over single phase.

Would you consider supplying photos for circuit board etching.
Or even sell circuit boards? For your inexpensive controller.

Also the part number of the correct motor for your controller . Or a picture of the nameplate
Thanks in advance.

 

[safe]

Yeah, I plan to keep people updated as the project unfolds. I'll probably start a fresh new thread once the motor arrives and I start to investigate the feasibility of using it.

Math Thoughts

The math favors AC motors with thin wires and high voltage because heat is directly related to current with a relationship that is squared. (Heat = Current * Current * Resistance)

Most AC motors are built around the standard line voltage of 120VAC or 240VAC. Now it's possible that I could throw in a voltage doubler (losing 10% efficiency before I even get to the motor) but I'm thinking that if I rewire the motor with thicker wires that it will (like with the rewinds) remap all the motor relationships to the lower voltage of 48 volts my batteries provide. This custom motor should then behave much better than if I left it stock. (48 VAC Induction motors are rare... though I did read one internet link about someone that had one, so it does appear possible to do)

Also...

Speed is a function of FREQUENCY with AC motors and not voltage... so it's pretty possible to keep the rpms down if you want in the 3000 rpm range or less.... at least that's how things appear to work at my present level of comprehension.

I'll probably create a completely separate circuit that is the current sensor and then use that as an "Armature Current Limiting" technique that is independent of the microchip. That chip has "ramping" built into it already, so it should be fun to play with.

 

[spad4me]

I believe that it would be easier with 48 volt rewind of a standard motor and live with the heat input from thicker wires.

The top motor speed of 3000 rpm run through a belt or chain reduction to achieve approx 400 to 450 rpm wheel rotation would be nice.

Current limiting as in a fuse or a speed limiter?
The locked rotor current draw ?
The initial high torque start from 0 rpm to maximum speed minus slip is intended to be controllable with your frequency controller, independent of a transmission .
I am looking for an electronic transmission. or equal.

 

[safe]

There's a lot to fiddle with with voltage and current. The microchip has "ramping" and voltage startup settings, so I'll be getting into all of that.

Here's the main reason for switching to an Induction type motor:

...the efficiency is related to LOAD and not rpm. The permanent magnet motor can only get it's efficiency at a very specific rpm at any time and with a specific current to match.

Induction motors with a built in power limiter (1000 watts input) mean that you can start from zero mph and crack the throttle wide open and the motor will accellerate all the way to it's top speed and be near it's peak efficiency all the time.

With a permanent magnet motor you either have to "throttle fiddle" in order to preserve efficiency or you have to have a lot of gears and shift your way up.

The "Holy Grail" is the Switched Reluctance motor, but that's a technical hurdle that is even higher than the Induction motor, so it can wait for later. I figure I'm going to learn all there is at each step along the way.