Why are low-speed alternators much more expensive than high-speed?

high-speed?

The lower the speed the heavier the rotor and stator windings must be... same with car motors etc... one that revs 10,000 rpm will have twice the HP as one of the same displacement that is firing only half as much at 5,000 rpm.

the 10,000 rpm motor can be half the size.

Phil Scott

Physically they are much bigger - more iron, copper, per KW output etc than higher speed units at the same frequency. Voltage per turn depends on the speed. Number of poles depends on the speed and frequency-- larger diameter needed at lower speeds.

More poles. More windings. More money.

Bill

It is mostly because the auto industry uses millions of high speed alternators a year and there is economy of scale.