[crote]

Early electric motors were awful, because there was no good way to control their speed.

For example, DC motors used in some late-1900s trains still had a giant variable resistor in series with their motor, burning away a huge chunk of the power as heat to force the motor to run at a lower speed during acceleration. AC motors weren't much better.

Electric motors only became truly efficient when variable-frequency drive became viable, which was in the 1980s due to semiconductor innovation.

[mitthrowaway2]

Surely the variable resistor would only have been on the field winding. It wouldn't waste that much energy.

[bluGill]

Figuring out where to place it, or how to do this took time. I'm sure some early attempts were really bad.