[GRLUG] OFF TOPIC Electric Car

[Collin Kidder]

> I disagree with the statement that AC motors are more efficient. I have
> a high end furnace from Waterfurnace which has a DC motor for the
> blower. There is always a loss when converting AC to DC or DC to AC.
> Even with the loss, it was more efficient in ongoing electrical usage to
> use a DC motor rather than an AC motor.
>   
There are a variety of construction techniques for both AC and DC motors 
but ordinarily an AC motor is more efficient. As a bonus an AC three 
phase motor is extremely simple especially compared to a DC motor. They 
are more reliable because of this. Also, they are pretty easy to control 
speed and torque wise. Usually a three phase or six phase AC motor 
running at over 400v is the best bet in terms of price, torque, and 
efficiency. Obviously there are a lot of factors that go into any choice 
though.

It's not uncommon for three phase AC motors to get better than 90% 
efficiency. Granted, there are some DC motors which can also reach that 
sort of efficiency. It seems, though, that finding a 200HP AC three 
phase motor is a LOT easier than finding a DC version of the same.