Overview This listing is for a USED AC Tech SM405 Variable Frequency Drive. It is designed to provide variable speed control, soft starting, and reversing for small three‑phase AC motors. This unit is categorized as a compact VFD and is rated for 0.5 HP (0.37 kW) with 400–480 VAC three‑phase input, supporting industrial and OEM motor control applications that require reliable, space‑efficient speed control.