Hi,

Since i started studying a little deeply Electrical motors, they seems to be more "complex" than we think when we look into a real machine, so i doubt that Q (Torque) = KQ(I - io) is a good aproximation even because, what is considerable as "Constant Torque"?

Brushless motors (BLDC) is considered as a DC motor because we normally associate them to batteries and DC Sources, however they are more similar to normal AC motors than the "old" Brushed DC motor. The best designation is electronically commutated motors (ECM) and they are synchronous motors, this basically mean that the speed is fully proportional with the frequency.

So they can be analized with almost all equations and relations as the AC synchronous motor easily found on internet.

Guilherme