Electric motor size and efficiency

[McWigglebum4th]

In the world internal combustion the bigger the engine the more fuel it needs at 30mph

Is this the same in the world of EV?

So would a 500bhp electric motor use the same amount of energy as a 100Bhp motor if they are only producing 50bhp?

[anonymous-user]

Generally, yes.

Emachine losses are primarily from 3 areas:

1) Mechanical losses (bearings, windage etc) Bigger machines need bigger parts, with higher losses
2) Copper (resistive) losses: Not quite as simple, but the more torque you make, you either have more current or more turns. If you have more turns you may have a higher phase resistance and hence higher copper losses at all torques. If you have less turns, you need more current for any given torque, so again, higher copper losses
3) Iron losses. Basically, motor power scales with motor active material (magnets+copper+iron)volume. Iron losses therefore increase in line with the machine volume.


It's also worth noting that the actual Emachine is just one link in the powertrain. The vehicles inverter, battery systems and power distribution wiring also account for some significant losses.