Will Copper Induction Bring Motorized Bliss?

Given the initial and replacement costs for the batteries, any difference in the cost of the motors is insignificant. Always opt the most efficient motor/motor control combination, and justify the price by marketing the increased performance.

Copper is used in the rotors of present day Traction Motors for Rail Transportation and Off Highway Vehicles. Cast Aluminium is ok for general purpose motors, but has too much resistance for traction motors.

The use of induction motors saves on expensive rare earth magnetic material which presently are under the control of China. The technology to watch is switched reluctance which requires no rotor winding or magnetic material.

Useful characteristics of SR technology are price, massive torque capability, unprecedented acceleration ability, the capability to be held at standstill electrically and regeneration only when excited.

Disadvantages such as "coggy" torque at low speed can be engineered out.

Permanent magnet has the advantage of always regenerating without the need for excitation, high torque capability and efficiency.

The disadvantages are cost and fragility of the rotor along with strategic nature of the materials.

Induction motors have advantages of cost and they are highly efficient,but are slightly less efficient than permanent magnet and on a par with SR. In common with SR they need excitation to regenerate. Fine torgue control suffers slightly in the slip band, SR and PM both being synchronous are locked to the rotating field but care must be taken to ensure they remain synchronous so that torque does not fall (or completely fail).

In summary each design has some advantages and disadvantages which can be applied to particular applications.

Some instances of this are, LeTourneau utilise SR for their latest loader designs (with a loader the ability to electrically brake ((at standstill)) instead of merely retarding is beneficial). Trucks and locos are currently utilising Induction Motors. In truck and loco application strong retard is required but stationary electric braking is not felt to be necessary. Hybrid hydraulic excavators utilise both SR and PM technology on the one machine with the advantages of each exploited thoroughly in the application.