Increasing iMiev engine power

[Llecentaur]

I can not find this blog again but someone definitely mentioned that there was a way to increase the power of the engine.

Any info on that ?

 

[JoeS]

If I recall, the Pike's Peak racer (not the i-MiEV) used our motors with controllers/software that greatly increased the motor output. Don't recall anyone on this forum actually modifying our little iMiEV.

 

[Don]

Not sure if they were 'our' motors or not . . . . but there were three of them

"Rather than the road car's single 49-kilowatt motor, the Zebulon Evo features three 80-kilowatt motors--two driving the rear wheels while one spins the fronts--and a 35-kilowatt-hour battery pack to keep the juice flowing on the way up the mountain. For reference, the stock car makes do with a 16-kilowatt-hour pack."

Of course, a more powerful motor requires either a shorter trip, or a more powerful battery pack . . . . or, in the case of the EVO - BOTH

Don

 

[Llecentaur]

Would be nice to have a choice. 80 KW would be great !

But regarding power vs trip distance. Won't the range stay the same if the driver uses the same amount of power, same speed and accelerations. Assuming he will not give up to the temptation to floor it :twisted:

 

[aarond12]

I believe our controller greatly reduces power to the motor at low RPMs, likely for power conservation and tire conservation reasons. Ever "floor" your i-MiEV from a stop? The power meter does not immediately jump to the top.

If someone could reprogram the controller to allow for a larger amount of power from a stop, that would make a great difference in how this car feels, and might significantly improve 0-60MPH times.

 

[Don]

I believe our controller greatly reduces power to the motor at low RPMs, likely for power conservation and tire conservation reasons. Ever "floor" your i-MiEV from a stop? The power meter does not immediately jump to the top

That's because we have a permanent magnet A/C motor and not a series wound DC motor

http://evauthority.com/dc-vs-ac-electric-car-motors/

With a DC motor, you can basically apply full current to it from a stop which creates really strong magnetic fields in both the rotor (armature) and the field which gives it tremendous power right from zero RPM's. All drag racing EV's use these DC motors just for that reason

Our A/C motor has a rare earth permanent magnet rotor, so the strength of the magnetic field is limited by the magnets, especially at low RPM's. At zero RPM, we can't create a stronger magnetic field than the permanent magnet is capable of for instant torque like a series wound DC motor can, so applying more current doesn't gain us anything - We're still limited by the fixed magnetic strength of the rotor. But . . . . since the rotor has no windings, the speed you can spin it is really impressive. Where anything above about 5,000 RPM will throw the windings off of a series wound DC motor, PM A/C motors can spin 2 or 3 times that fast

We give up some low RPM torque for all the other advantages A/C motors have, such as higher efficiency, lighter weight, very high RPM which means we can go from zero to 80 MPH with only a single gear ratio and no shifting needed . . . . and, of course we also get regenerative braking which is just about impossible to do with a DC motor

Another advantage - It's pretty hard to burn the tread off the tires :lol:

Don

 

[aarond12]

Very good article and info from you. The article, however, is a bit dated. (The reference to the new Dodge EV gave it away.) Has anything changed in the world of AC EV conversions? Has price gone down from "$50K" like the article said? I'm sure it has by now...

 

[Don]

I'm sure it has, based on the car we have in our garage

Cost wise, the big difference between A/C and DC is that we need a 3 phase inverter (to generate the A/C field our motor uses) whereas the DC variety only needs a simple DC current controller. That and the circuitry associated with the regenerative braking means A/C powered cars need lots more fancy electronics to function than simple DC powered cars do, which is why most home brew conversions are usually DC powered and many of them require you to keep the transmission if you want both good low speed power and still have the ability to drive at freeway speeds

I just picked that old article because it explains some of the differences between A/C and DC motors and why we don't have the instant torque the DC variety has

Don

 

[peterdambier]

I guess time changed things a bit. DC has a single driver. AC has three of them but needs only one third of the power.

DC needs pulses to build slices that resemble fractions of the supply voltage. With AC those slices are modulated to build something that looks like a sine wave. It is the same thing only with AC the micro controller has three outputs each of them shifted by one third of the circle.

The only complication is taking care of the position of the drive shaft to make best use of the the torque but that is strictly not necessary.

We have more elaborate software but in masses on open source software gets better and cheaper.

 

[Don]

The A/C drive systems lack of torque at stall is actually a positive for automotive applications . . . . unless you're drag racing - If you have max torque available right from zero RPM's the entire driveline is subjected to very great stresses which can break things . . . . unless you overbuild transmissions, axles, CV joints and the like, which adds weight

FAVORABLE TORQUE

"This means that AC electric car motors can be well matched to your gas-guzzler's torque curve so that you don't inadvertently murder your transmission with your normal driving habits. The gas-guzzler's engine is considerably different than an electric DC motor, and the drive system your donor was born with is not designed to withstand the low-end workout your series DC motor is capable of delivering. The AC electric car motors are much more...diplomatic, and your transmission will last longer. How does Metric Mind put it?..."broken gear teeth, stripped splines, twisted shafts, damaged CV joints....AC setups don't have these issues."

Don