The AC Induction Motor Ebike Project

Have you seen the 5 to one transmissions that are starting to be used by Thats dax , and the scooter guy.
I have also built motorized bicycles using a cvt that that changes ratio from 6 to 1 to 3 to 1 by centrifugal force
Or the front freewheel that results in a peddlable jackshaft.
This enables the so called shift kits to utilize the rear dérailleur.
 
Without the coils energized there is no magnetic field .
So there is some drag not much. You are still spinning the iron rotor.


And yes you can throttle down to get regenerative braking if you design for it .
 
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(geardowns)

Been there, done that...

The whole idea here is to eliminate the geardown element of the ebike. There is an efficiecy loss with mechanical geardowns that you can avoid if you use a motor with a low enough rpm.

It looks like a Three Phase 4 Pole motor will get the job done.

I wonder how common 4 pole AC Induction motors are compared to 2 pole?

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Ironically the Tesla Raodster uses a 4 pole Three Phase Induction motor, so it seems that once you stumble upon the math it eventually leads you to the most obvious answer. The most practical way to get a self starting motor with good low end torque, low rpm is with the 4 pole Three Phase motor.
 
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I am also trying to get away from most of the unnecessary complex gear down setups.

I have installed a very large number of three phase motors.
And to be candid I never even thought anything about what type, so I can not say.
Other than a common capacitor start single phase motor is actually a two phase motor by virtue of the phase shifting cap in the motor design.
 
Three Phase is generally considered a better technology. From the standpoint of efficiency the Three Phase is supposed to be better. As just posted above, the Tesla Roadster uses a 4 Pole Three Phase AC Induction motor and so that's not a bad example to copy. Single Phase has the advantage of being simpler and can allow for lower motor speed.

Sometimes you just have to make a decision and give it a try... R & D.. see where it takes you...
 
Three phase power was invented for industry.
Reliable and powerful as well as cheap.
The future seems to be split into two groups the Japanese who use rare metals .
And the Americans who use three phase power with commonly available materials. Copper iron aluminum.
The main supliers of rare metals the Chinese are all ready hoarding rare earth metals for their own use.

I have to go my eyes are tired.
My seasons are reversed from yours Now I am trapped inside by extremely high tepmperatures.
And in the Winter I enjoy 80 degree days .
I was running out of projects that can be done indoors this project fits my needs well.
When metal becomes so hot it can brand you if it faces into the sun for a few seconds .
You try to work inside.
 
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Star (Wye) vs Delta

For lowest rpm you need to go with the Star (Wye) connections.

attachment.php


...most of the 4 pole images I've seen have them connected as Star (Wye).

Doing a 4 pole with a Delta is sort of a self contradiction because if you are trying to reduce rpm why would you then wire it together to increase rpm? That wouldn't make any sense. However, for a two speed system I could see it, but I think that I'll have plenty of rpm already. I'll be on the high side of rpm as it is... don't need any more...
 

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Leave extra wires when hooking up your motor to try both .

You are correct that the reduction you want favors wye .
I still will use a delta configuration myself.

I could be mistaken but I don't think so in recommending a delta preference.

Your project is greater than my expectations .
I just priced a factory made three phase controller. starting price at $100.00. for motorized vehicles.
OUCH !


On the maytag motor
One place even claimed it could not be done as a hobby too complex.
BUT
I may have inadvertently found a controller that will work for a maytag washer motor.
I have to check some more.
No this looked like a fix using hall effect sensors with a variable speed control. not for the maytag though.

I will need to start from scratch .
I have no battery, yet .
It will take me a while to get where you are.
Just building a lot of parts.
 
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The Consequences of Lower Voltage

Toys should not kill.

Ebikes are in effect "toys" and so if some kid accidentally electrocutes himself with their ebike they should not die from it. It only takes about 50 DC volts to kill someone.

So I really want to design this AC Induction motor to be able to operate at the very low voltage of 48 volts. This is half of the standard line voltage and I found this link that discusses it:

http://www.motorsanddrives.com/cowern/motorterms12.html

When electric motors are subjected to voltages, below the nameplate rating, some of the characteristics will change slightly and others will change more dramatically. A basic point is, to drive a fixed mechanical load connected to the shaft, a motor must draw a fixed amount of power from the power line. The amount of power the motor draws is roughly related to the voltage times current (amps). Thus, when voltage gets low, the current must get higher to provide the same amount of power. The fact that current gets higher is not alarming unless it exceeds the nameplate current rating of the motor. When amps go above the nameplate rating, it is safe to assume that the buildup of heat within the motor will become damaging if it is left unchecked. If a motor is lightly loaded and the voltage drops, the current will increase in roughly the same proportion that the voltage decreases.

For example, a 10% voltage decrease would cause a 10% amperage increase. This would not be damaging if the motor current stays below the nameplate value. However, if a motor is heavily loaded and a voltage reduction occurs, the current would go up from a fairly high value to a new value which might be in excess of the full load rated amps. This could be damaging. It can be safely said that low voltage in itself is not a problem unless the motor amperage is pushed beyond the nameplate rating.

Aside from the possibility of over-temperature and shortened life created by low voltage, some other important items need to be understood. The first is that the starting torque, pull-up torque, and pull-out torque of induction motors, all change based on the applied voltage squared . Thus, a 10% reduction from nameplate voltage (100% to 90%, 230 volts to 207 volts) would reduce the starting torque, pull-up torque, and pull-out torque by a factor of .9 x .9. The resulting values would be 81% of the full voltage values. At 80% voltage, the result would be .8 x .8, or a value of 64% of the full voltage value.


Most of the amperage ratings I've seen for these AC motors are around 5 amps or less. I know that in order to obtain my desired 1000 watt input power with 48 volts that I will need about 20 amps of current. So somehow I need to be able to change the windings to be able to handle roughly four times the current.

It will be interesting...

The only positive in all this is that I've been looking at the way that the variable frequency drive works and apparently they PURPOSELY lower the voltage during starting so as to protect the motor. So I have a feeling that the net result is going to be something where you gain some things in some areas of the powerband and lose in others.

My guess is that if you are faced with a large load and your throttle is declaring a frequency desire for the motor that is producing a lot of "slip" that it will draw a lot of current. If you had a feedback (closed loop) system that would do a "throttle pulldown" to a lower frequency you could protect the motor from overheating itself with excess current. (sort of the Armature Current Limiting concept)

The AC controller chip has ramping which is sort of a blind way to try to get a current feedback loop. Ramping just means that the "normal" acceleration is going to be limited to a certain rate. Ideally a current sensor feedback is better than ramping. (though ramping might be good enough)

The "bottom line" is that low voltage will mean higher currents and so that's a central thing to be focused on....
 
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