# ac induction motor bike

#### Toby woodman

##### Active Member
i have an 850 watt generator and a 750watt induction motor spinning at 1500rpm, if i gear it with a 4:1 reduction for a top speed of just under 30mph, and use a speed controller, would this be able to power a bike. I'm not looking for power or speed, and i am expecting to pedal on steep hills, however, would this work to a certain degree?

i have an 850 watt generator and a 750watt induction motor spinning at 1500rpm, if i gear it with a 4:1 reduction for a top speed of just under 30mph, and use a speed controller, would this be able to power a bike. I'm not looking for power or speed, and i am expecting to pedal on steep hills, however, would this work to a certain degree?
What you have to consider is what the amp rating is for the wire windings inside of the motor. For example with the 750 watt motor, if it's operating voltage is 120 volts that means 6.25 amps is flowing through the motor windings. To get the same 750 watts with 48 volts there'd be 15.625 amps flowing through it. Therefore the windings have to be able to handle the extra amperes. Otherwise the motor will over heat.

What you have to consider is what the amp rating is for the wire windings inside of the motor. For example with the 750 watt motor, if it's operating voltage is 120 volts that means 6.25 amps is flowing through the motor windings. To get the same 750 watts with 48 volts there'd be 15.625 amps flowing through it. Therefore the windings have to be able to handle the extra amperes. Otherwise the motor will over heat.
Could you repeat that? I missed the middle part. Maybe use a toaster to explain.

the motor is single phase 230 volt ac with a 750watt power rating, i would run it off a 850watt 230volt generator without changing the voltage, a direct drive so as the speed controller is turned up, the motor draws directly off the generator

Could you repeat that? I missed the middle part. Maybe use a toaster to explain.
Basic electric formulas

W=VI
V=IR

In other words if you're going to push more current through the motor with less voltage the motor has to have a lower resistance in order for the wattage to remain the same.

Single phase ac motors have no starting torque. Look into 3 phase motors and vfds if you want to use an ac motor for a build.

If you can find something like this

and a 230v 1hp 3 phase motor that ought to work well enough.

Also there are bldc motor controllers that will happily take the 145vdc you'd get from rectifying the output of that generator.

Are we talking one of those hand carry generators like a Honda 2200 watt?

Are we talking one of those hand carry generators like a Honda 2200 watt?
Yeah

If you have a bike trailer that can handle the load or are willing to make one, that would be the best way to carry the "portable" generator.

Assuming a rear rack, left side drive, getting the 4:1 ratio is plenty easy if the motor has a mounting foot.

I would detune a centrifugal clutch to engage at low rpm, like 600, so the mass of the motor can act as a fly wheel to help with starting torque. Hardest part is finding a spring with the right width that is weaker than the stock spring.

The single phase fed vfd will be the most expensive part. I love small 3 phase motors, small and simple but useful. Most have what's called a drip proof open enclosure which means its fine in a sprinkle or getting splashed briefly but isn't totally sealed up. This is actually a good thing because a small cooling fan is coupled to one side of the motor keeping it nice and cool even when mildly overloaded.

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