single phase motor speed control Page 8

Controlling speed on a single-phase motor isn’t a dimmer-switch fairy tale—it depends on the motor type. Induction/PSC motors want a VFD (variable frequency drive); dropping voltage with a cheap controller makes them hot and sad. Universal (brushed) motors can use a triac/dimmer-style controller, but expect more noise and less torque, so use a proper soft-start unit. Shaded-pole/PSC fan motors sometimes accept dedicated fan-speed controllers, but torque falls with speed—fine for blowers, not for pumps or compressors. For wide, stable control, many folks swap to a 3‑phase motor + VFD or a VFD specifically rated for the single-phase motor in question. Mains is 230–240 V here, so get a licensed sparkie and ensure compliance—no heroics with bare wires.