Re: Good article on brushless DC?
Much of this depends on how motors are rated. Industrial 3 phase motors are very conservatively rated and take into account ambient temperature and normal overloads and will run at their continuous ratings for months and even years with little attention and a high degree of reliability. Size and weight are of little cocern for something that is bolted to a factory floor and just expected to deliver it rated torque, speed, and power all day long and just occasionally perhaps need some minor maintenance like cleaning and lubrication and sometime snew bearings.
Vehicular traction motors, especially for non-rail applications, have much greater premium on size and weight, as well as efficiency, and that can be difficult to achieve. It seems like the motor of choice has become the BLDC, and there are many such motors with amazing specs, but often I think these are greatly exaggerated and you must look carefully at the duty cycle and the temperature rise and special requirements such as liquid cooling. The controllers are often rather exotic and expensive, and the motors are costly and fragile because of the rare earth magnets.
A properly designed AC induction motor can fairly easily achieve a 2x-6x boost of power by using high quality laminations and good controllers so they will come close to matching the specs of BLDCs. And my research and experimentation with switched reluctance motors show that they may well be even better than BLDCs in the long run.
The electric motor industry seems to stay in certain "comfort levels" of what has been well proven in the past, and true innovation is considered risky and is often promoted by small companies who really don't have all the proper testing equipment and data, and are anxious to "jump on the bandwagon" with their "new" designs which they promote in the hopes of quick sales and immediate success.