The AC Induction Motor Ebike Project

[safe]

It was a 2 pole Single Phase motor before I removed the wires.

This process will be like learning to rewind the DC brushed motors... I will eventually figure out how the windings need to be, the thickness of the wires, the number of turns and eventually I'll focus on better and better results.

It's a "process" that's for sure.

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Here's the "enhanced" way to figure out the true speed. You actually divide the phases from the pole count. Interesting.

 

[Proudest Monkey]

Ok I gotta admit...I'm impressed..

But how come noone's talking about miniature reactors?
If they can put em in submarines....

 

[spad4me]

Ok I gotta admit...I'm impressed..

But how come noone's talking about miniature reactors?
If they can put em in submarines....

The lead shielding would weigh too much.

 

[Proudest Monkey]

No I was thinking more along the lines of a Russian design....less shielding...but could probably only be ridden for 1-2 minutes at a time before it rads you out..


I just put a CB with 5' antenna on my bike...so...anything's possible...

 

[spad4me]

Safe, I just found a battery thread that shows your battery setup.
How long does it take to charge the twelve sets of 20 nicads.
Have any failed yet?

 

[safe]

The batteries have worked flawlessly. They charge up in about an hour depending on how drained they were. My first set on the older bike went for a time before I got the random and expected flawed cell. No problem, pop open the battery and like a flashlight I just replaced the problem cell.

It's so good that it's kind of puzzling that it's not done by others yet.

The idea doesn't work for anything but NiCad or NiMh though... so since everyone is all excited about LiFePO4 these days you can't use it for that.

NiCads are indestructable and can last for a decade...

 

[safe]

Taking A Closer Look...

This is very important and worth a second look. Most of the documentation about AC motors tends to use the term "poles" very loosely and I think I got the wrong idea about the relationship between "phases" and "poles" at first. The main thing is to realize that it's the number of subdivisions within the total poles available that defines the motor rpm.

So the EXTREME would be to use a Single Phase motor and wind it as a 12 pole design. The motor speeds that you would expect would be:

Low Throttle:
Single Phase with 2 Poles = (120 * 10) / (2) = 600 rpm
Single Phase with 4 Poles = (120 * 10) / (4) = 300 rpm
Single Phase with 12 Poles = (120 * 10) / (12) = 100 rpm

High Throttle:
Single Phase with 2 Poles = (120 * 60) / (2) = 3600 rpm
Single Phase with 4 Poles = (120 * 60) / (4) = 1800 rpm
Single Phase with 12 Poles = (120 * 60) / (12) = 600 rpm

Low Throttle:
Three Phase with 2 Poles = (120 * 10) / (2) = 600 rpm
Three Phase with 4 Poles = (120 * 10) / (4) = 300 rpm

High Throttle:
Three Phase with 2 Poles = (120 * 60) / (2) = 3600 rpm
Three Phase with 4 Poles = (120 * 60) / (4) = 1800 rpm

...based on the gearing that an ebike needs the Three Phase with 4 Poles would be okay:

Pedal Speed - From 0 to 100 rpm

Motor Speed (11-55 sprockets) - From 60 to 360 rpm

...so the pedal power would cover the lower rpms best and then the motor kicks in strongest to take the motor above 100 rpm. Pedal power would be your "extra boost" to get things going from a standstill.

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It's just like with rewinding DC brushed motors, depending on the way you wind them you get different behavior. The behavior we want for ebikes is a motor that develops it's power at lower rpm so that the gearing can be accommodated more easily. The Single Phase motor has a problem in that it cannot guarantee to start in the right direction and the (rare) Double Phase cannot guarantee starting either. So from a practical standpoint you need to go with a Three Phase. If you could increase the number of grooves in the stator from 24 to something like 48, then you could have more options. The standard stator uses:

24 grooves
12 poles

...which can be wound as:

2 pole, 4 pole and for Single Phase only 12 pole.

 

[spad4me]

You have it .
The starting problem can be overcome by shading one pole, a thick conducting wire at an edge of the rotor., or just pushing the bike then goosing the throttle.

There is delta which is phase--- a to b, b to c, c to a. Then double delta just parallel.
Wye which is ,a phase to ground, b to ground and, c to ground . In this case ground is a common attachment point that ensures a stable refrence . A stable ground is not needed here. There is also double wye .
The oddest setup is called a schnidt transformer it is dangerous in that one of the legs has an unusually high voltage which by law is marked with an orange band where ever this voltage is present in a junction box.
I recommend a delta wiring solution over all others

I was looking at batteries and of course the iron based liithium batteries came up. two thousand dollars is just too much I believe that your nicad based solution will work just as well.

 

[safe]

Delta produces the lowest rpm right?

Probably the main thing to have learned (for me) is that the Phase count is less critical than the way the poles are connected together. The way they usually explain the poles is not very clear in many cases. I'm glad I found that image because that cleared it up pretty quickly.

I don't think that it's even necessary to go to Single Phase just to get the chance to go 12 Pole. I think that 4 Pole and Three Phase should cover it.

From above:

Pedal Speed - From 0 to 100 rpm

Motor Speed (11-55 sprockets) - From 60 to 360 rpm

 

[safe]

Single Phase, Pedal Start, Regen?

If you eliminated the rear freewheel and just used a single front freewheel then the chain would always be connected to the motor. You then create a "pedal first" setup where you cannot use the motor until you pedal first to get the rear wheel moving in the right direction. Since the chain is bound to the motor all the time you can now do regen on the rear wheel. If you cut the throttle to zero then there is no backEMF because induction motors only create a magnetic field if they are dealing with a preexisting field, so if you shut the throttle completely it allows the motor to freewheel. Ramp the power down and you would get the full regen until the field collapsed.

That's all possible isn't it?

It would allow for a very, very low rpm motor because a 12 Pole would produce:

Single Phase with 12 Poles = (120 * 10) / (12) = 100 rpm
Single Phase with 12 Poles = (120 * 60) / (12) = 600 rpm

Pedal Speed - From 0 to 100 rpm

Motor Speed (11-55 sprockets) - From 20 to 120 rpm

...that's almost TOO SLOW for the motor.