On 2016-02-07, Martin Eastburn wrote:
Electrical motors were silent or near so. They also could be speed
controlled. Most heavy equipment - big stuff are electric with
generators either on board or down the way.

The massive excavators that are digging the soft coal out of the near
surface seam in Central Texas are electric. There are massive cables
that snake across the ground that feed the monster so it can move about.
I think they are AC lines from a powerhouse made for the purpose.

Yes, this is exactly right.

i