How can I calculate a permanent magnet load line?

Hi Every one,

TESLAs idea of using induction motor is wise. But my question is how long would it stay to be competent performance wise when others better motors are coming.

Of course everything that is said about induction motor (check the link I put below for information on TESLA website) is right except concerning weight or size and power density related matters. AC Permanent magnet motors are also a good candidate for its higher power/ torque density, compact size ( for the same rating as induction machine), better speed range, ease of rotor angle measurement precisely from position sensors (unlike IM machine DRFO control scheme which entirely depends on stator voltage and current measurement to calculate the rotor angular position but suffers from DC offset and Stator resistance change due to temperature; or IRFO scheme still has rotor resistance variation).

Induction motors performance in field weakening constant power region is better of course as less magnetizing current demand but we have to look also its performance at low speeds in constant torque region - it  has low speed performance efficiency is low, we have to deal with the heat loss from the rotor which leads to low p.f and efficiency, speed range is not wide, rotor resistance variation due to temperature makes it difficult to measure precise rotor angular position especially during field weakening and this sends a false information about rotor position to the PI or PID controller. This whole thing makes the controlling of IM machines very complicated and I am not sure how much this costs.

Using induction motor for vehicle at this current time is not a bad idea as we don't have much alternative to get a better high power (magnetic flux) magnet. As we know the rare earth metal is dominated by one country (China). But soon, all our fuels will be depleted and we have to upgrade or enhance our air crafts and ships to more electric and then to full electric operated ones. Especially for aircrafts, we need a more compact, small weighted, high power/torque density motors and in this case, AC PM machines are our only alternatives at the moment (this is my opinion) and if scientists succeed in  inventing a high power permanent magnet from super conductors (on research to create a magnet at nano scale level),....my friends...this will change every thing.

Please check the link below.