The AC Induction Motor Ebike Project

Why Not The Fifth Harmonic?

The Fundamental is a simple sine waveform. The Third Harmonic adds two waves located with one on either side of the Fundamental and drops the "effective" rpm by a factor of three. (from 3600 to 1200) The Seventh Harmonic adds two waves on each side of the fundamental and drops the "effective" speed by a factor of seven. (from 3600 to 514)

What about the Fifth Harmonic?

The problem with the 5th, 9th, 13th, etc Harmonics is that the peak of one of the waves ends up aligning with the Fundamental and that makes the overall peak much higher.

When you see it visually is makes perfect sense... you just can't use the Fifth Harmonic !

Not only this, but for Six Phase power the Fifth Harmonic actually SPINS BACKWARDS relative to the Fundamental and so in effect it would act like a brake. :sick:

You just can't use it...
 

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Samples

Here are some sample waveforms that are to scale. Notice how the lower rpm waveforms are scaled (based on the Voltage vs Frequency table) so as to keep the motor from excessive heat build up. As the motor speed increases you can increase the wave height because each phase holds the current for a shorter period. This gives some insight into why a Six Phase motor can potentially achieve higher power levels because each phase holds it's current peaks for shorter periods of time. This is a lot like the Agni motors (Lynch pancake design) which uses hundreds of little commutations rather than the few that most brushed motors use. The more you smooth out the current delivery the more you increase the average. Peaks of current increase heat much more than averages because the current produces heat based on the square rather than being linear. The theoretical limit is when the entire stator is at it's saturation level. (all the way around) Once you reach that point you cannot achieve any more power.

500 rpm - Seventh Harmonic

1000 rpm - Third Harmonic

2000 rpm - Fundamental

3600 rpm - Fundamental
 

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Project Cancelled

It's been a great educational experience... and many of the ideas I plan to use on the next project.

The Halbach Axial motor design has simply proven (in my mind) to be the better path for ebikes.

I'm glad that I learned all this stuff... and I'm as confident as ever that this idea of getting to a wider powerband was the way to proceed... but the Halbach design is so attractive because it offers the benefits of using permanent magnets AND the benefits of a wider powerband.

The Halbach motor is simply all one could want. :cool:
 
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Until I see a piece of information that disproves the Halbach design I'm going to "upgrade" to that. They both use AC power and have similiar powerbands, but the Halbach just works better, is easier to design with, and weighs less.

Everyone knows about pancake motors, but there are two categories of pancake motors, the "standard" design and the Halbach. I've known about the "standard" design for years now, but somehow the Halbach slipped past me and I only learned of it a few days ago.

For ebikes the Halbach is a big improvement over the "standard" because the modified powerband resembles the AC Induction motors powerband even though the Halbach is actually (technically) synchronous.
 
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AussieJester was laughing because I thought (for some reason) that I was using a 100 amp controller by mistake. By the time I actually got out to the garage and took the controller apart to find out what I was running he was banned.

As it turned out I had set the 60 mph downhill speed with a 36 volt 40 amp controller that had no modifications whatsoever. I was running it with 48 volts though.

It's true that I own a 100 amp 48 volt controller and was afraid I got it mixed up. (that was an error... I wasn't using it)

The "final realization" on the rewinds was about brush spring pressure.

Man I wish I figured that one out a few rewinds ago. :sick:

Once you increase the spring pressure it reduces the brush heating and that keeps the commutator cooler. That's something no one figured out... so I just got lucky to have found a paper online about it. The stock spring pressure is too low for the extra power. Brush timing is another factor, but it's not as important as getting the spring pressure right.

So on the negative side, AussieJester, from your perspective you still have to explain how I was able to reach 60 mph (downhill, flat is from 45-50 mph) with only 40 amps. :cool: (the answer is kind of obvious... it's all about aerodynamics, aerodynamics, aerodynamics :whistle:)

But it's good to be skeptical... never just take someones word...

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I went really conservative on this last rewind, so the speeds and power are down compared to some of the others.

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Getting Back To The AC Induction Motor



I don't normally read things at Endless Sphere, but since I was consulted on some of the ideas in the process of this project going together I have added a link to it to watch.

Frankly... I don't know... if the AC Induction motor can be the winner in the long run. There is a clear need for a low cost, low rpm, high performance motor and "in theory" the AC Induction motor has a lot of potential. I was kind of shocked at the 50 lbs that he's using for the motor. My motor will be about 10 lbs and is roughly of the same size as the Unite motors. I plan to really drive mine hard and do all the "hard work" of figuring it out rather than just buying stuff off the shelf.

It's good to see a first project working... but it's far from where I think it needs to go before people accept it as the correct solution.

The main goals are:

:D Eliminate the need for Geardowns.

:D Eliminate the need for Multispeed Gearing.

:D Adhere tightly to the 1000 watt / 750 watt Power Limits.

:D Remove the Inverter and Rewind the motor to Optimize for lower voltage.

:D Equal (or exceed) the best that any other technology can produce.

...it's a tough problem. :rolleyes:

A solution to many problems as suggested and a few more!
1 start off with a 5 pound 1500 to 4000 RPM 1000 watt rated motor at 88 to 93% efficiency. This would consist of a 5 1/4 od Stator and a 4"dia rotor with 12 or 14 poles usig N-50-H hi temp magnets. Parallel Y windings to fill the lams up with the most copper with the right amount of turns to get a kv of about 55.5 RPM per volt with about 4 to 5 lbf·ft per amp in 3 phase design where the freespin rpm does not have to many losses until above 5000 rpm. The super inductance from the PM rotor design is what will supply instant on demand torque as needed and still have a wide rpm efficiency. The size required of a aluminum case would be 5.25"od X 2.5" with a 1" X 17mm or 5/8" shaft.

2 Motor drive sprockets from 9 teeth to 14 teeth (12 tooth is preferred for the average hills) Composite wheel hub sprockets on a gokart type hub adapter from 80 to 92 teeth. (90 tooth is preferred for steep hills) and over 25 mph on the flats on a single ratio.

3 The right chain for each drive. A 1000 watt motor used with either #35 or #219 chain adjustment is minimal and you will never need to replace the chain. The pedal chain can go straight to a derailer or a multi speed infernal gear hub. Using a 1000 motor to a legal speed of 20 MPH on the steepest hills Anywhere you only need ONE gear ratio for exlent performance and efficiency at any speed up to 25 MPH at 72 volts. The single reduction for the motor can go on either side of the wheel and can go on either side with the use of a derailer Multi Gerard hub or Both using a Sram Dual Drive hub with a freewheel for the motor and a pedal chain freewheel ot freewheel cassette used in common with 3 speeds that shift the motor and pedal drive at the same time. The sram Dual Drive with both the chains on one side is the nicest if you can find all the parts. The low gear and the high gear allows for extra high torque for extra loads on hills and the 3rd gear allows for good motor efficiency up to 45 MPH. You can pedal up to about 32mph with a cadence of close to 100 rpm. A easy fix is to shift up the next larger size pedal chain-ring. A bike without pedals is a breeze to adapt.

3 Finding a bike you can mount it on with some batteries.

4 FUN!:cool:

Try to get your state to allow it ?



 
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Disassembly
This older motor was a Single Phase
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The Single Phase motor is listed as 3450 rpm for 60 Hz.

I see that the thread was closed a long time ago, but that was the only place I could find that someone tried using a dishwasher motor for something else than a dishwasher.
I have couple of these motors, they look very similar to one posted on the 1st page of the thread. They also rated at 1/3HP and 3450 rpm. The only difference, they have 4 wires, not 3.... Does anyone have an idea if these are also Single phase motors? Is there a way to find that?
 
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