Which is better for an automotive application? Which is more efficient? Let’s assume they are both 3 phase units and that the BLDC uses rare earth magnets.
Maybe I am just ignorant, but how can a DC motor be three phase?
I think the distinction is that the windings of both motors require polyphase power, but the induction motor has to be fed this polyphase power whereas a brushless motor is fed DC power and creates the proper phase relationships itself using the switching circuits that replaced brushes (and a brush motor does the same with its brushes and commutator).
Do you have three phase power available in the automobile? Why? It’d be rare for an automobile, unless you’re counting raw winding output from the alternator before its rectifier.
Both kinds of motors can be pretty efficient. The most efficient motors in the world are 3 phase, but they have to be made pretty big to get the highest efficiency.
Sorry let me clarify myself. I’m referring to electric cars (or hybrid) where you’d have a big battery bank and then the motor would drive the car. A controller is needed to invert the DC voltage into a simulated AC sin wave.
Here’s what Tesla (the company, not the guy) has to say.
This article discusses a lot of the issues involved. The author concludes that brushless motors will probably continue to dominate the electric vehicle and hybrid market, where induction motors will probably remain dominant in high performance vehicles. I personally tend to agree with his assessment.
ETA: Should have previewed. While I was poking around I got ninja’d. Oh well.