Star delta starter for heavy motor loads, 400 A AC-3
Its 400 A rated operational current in AC-3 utilisation category (switching squirrel-cage motors — starting, stopping, and inching) means it handles the high inrush and inductive break of motor starts without welding contacts or exceeding temperature rise limits. The 115 V AC 50/60 Hz control coil pulls 1075 VA inrush at 20 °C, so the control transformer and wiring must be sized for that peak — not the holding dissipation of 14 W.
AC-3 duty at 400 A is the headline number: it governs the motor current the starter can switch under full load, not the resistive heating current. The associated fuse recommendation — 500 A gG or 400 A aM at ≤ 440 V — tells you the upstream protection must coordinate with the starter's 3200 A rated breaking capacity and 4000 A making capacity per IEC 60947-4-1. The 40…65 ms closing and 100…170 ms opening times are fast enough for sequential star-to-delta transition without overlap, provided the control logic respects the 20 s starting time window. Mechanical durability of 10 Mcycles and a maximum operating rate of 2400 cycles per hour at 55 °C mean this starter is rated for frequent cycling — conveyor lines, pump stations, or compressor duty where starts accumulate. The 3000 m altitude derating factor applies above sea level; if the panel sits at elevation, the AC-3 current must be reduced per the manufacturer's curve, though the evidence does not state the exact derating slope.