View Full Version : What is the difference?

03 December 2014, 1420
I am on a quest to understand more about EV's and their motors and i think i understand the difference between DC and AC motors pretty well, what is the difference between the motors for sale on EV sites and the electric motors on lets say a gas generator or washing machine? I ask because i was just curious due to my friend's family owning a scrap yard local and they get tons of gas generators tossed away for scrap metal and many of these are like 10kw+ units that just sat around and the carb gunked up.. so he typically rebuilds them and resells the whole generators.. but occasionally he gets ones that were damaged when tossed so the electronics are bad but the motors look plenty fine.. Are these type of units capable to be a drive unit for a motorcycle?

03 December 2014, 1600
Sometimes you can reuse "outer world " motor for DIY project for saving some money ... BUT ....

motor born to be used from AC outlet are mostly AC induction , so are very heavy , also they have cast iron case , also heavy , and are poorly finned so they overheat easly, and most important the windings are made to be runned from three phase 400v , this mean that you need a 570V battery to run the proper inverter to get the right voltage ( and power) out of the motor.

High voltage battery can be very dangerous so people use lower voltage system ( from 48 to 120 volts) , motor need to be builded with this voltage in mind , so EV motor are optimized for this voltage range , you can run a normal motor at a lower voltage but you get only a small fraction of the power.

If you still want to try to use a three phase induction motor from a scrap yard you should look for a motor with a star (Y) windings and reconnect it to Delta , this will lower the nominal voltage of the motor and make it closer to normal EV voltages ( changing star to delta change the nominal voltage by a factor of 1.73)

For example a very common AC induction inverter for EV is the Curtis ( useful also in your case the autotuning function) , this controller have a DCbus of 96 Volt nominal , so the AC phase voltage is 68V (96*0.7) .

A Star scrap yard motor start with a phase voltage of 400V , switching the connection to delta it will make it a 230 volts motor , your curtis can supply 68 volts , so you will get just one quorter of the original motor power.

04 December 2014, 0402
Washing machine motors are usually brushed-DC motors and rated for no more than 1kW continuous - absolutely no use in a traction application.

Generators are induction machines, and as such they can be used as motors, but as Athlon says, there are mechanical and physical constraints in their design, and they require complex controllers in order to motor efficiently and at variable speed - this controller isn't something that you're going to hack together in your shed, and you're not going to buy anything effective off the shelf for any small change. The Curtiss controllers would be the right option if you were determined to go down this route, but you'd get far better value from a matched motor controller combination despite the additional cost.

If you're looking to experiment on the cheap then the best bet would be to look for an old golf cart, forktruck or even a prius if you really fancy a challenge - either will have both traction motor and matched controller although you're going to have to so some significant effort in the case of the latter.

The golfcart/forktruck would definitely be the easiest to do something with although they could have either Brushed DC or induction motors depending on spec. The latter is the preferred.