I recently discovered Temu — a site selling miscellanea at often hard-to-believe low prices. A lot of what they sell is standard Dollar Store fare (plastic kitchen implements and small metal tea infusers and such), but they also have some interesting STEM items for sale.
One gizmo that caught my eye was a “three-phase power generator” demonstrator. It’s a set of nine coils grouped into three phases around a stator, with an outrunner magnet rotor. Spin the rotor and the coils generate three-phase power, suitable to light some LEDs or perhaps (with some power conditioning) charge a phone or other USB device.
A small three-phase generator. They even include a LED to show that it works.
The generator comes apart easily, to show the coil configuration.
To show the sequential activation of the coil groups, I connected three red LEDs with consistent polarity from A-B, B-C, and C-A. I drove the generator shaft with a cordless drill set to a relatively low speed (just enough to provide sufficient voltage to light the LEDs), and filmed it with my phone in “Slow Motion” mode. This was enough to see the phase sequence of the coil activations. (With another set of three LEDs in the reverse direction, you could see the other half of the three phases, as well.)
