I’m currently reading through one of Bernie Tobisch’s books on sewing machines.
He mentions that older sewing machines have AC (alternating current) motors. These are simpler to build, but have low power at low speeds. He said this is why sometimes when first starting a seam, the sewist (which is a nice term, once I haven’t heard often) might have to turn the handwheel by hand to get the motor started.
He writes that newer machines have DC (direct current) motors. These have better power at low speeds. But they are also more complicated to build. Most houses aren’t wired for DC voltage. (I’m saying most because I’m sure somewhere there was someone who ran some DC power lines through their house.) Most houses in the U.S., 120 Vac RMS is what comes out of the wall. That will fry almost any DC motor. So, DC motors get used, but there’s more circuitry involved to make them work.
Somewhere I have a book about using small electric motors. I wanted to look at it the other day, so maybe I’ll spend some time this weekend finding it.