Load Considerations

Abstract

Power switching devices are employed for controlling inductive, resistive or capacitive loads. Inductive loads include transformers, solenoids and relays. High-current in-rush occurs with loads such as incandescent lamps, pulse-forming networks, snubbers and motors. Incandescent lamps are essentially resistive, but the cold resistive in-rush current during turn-on is 12–18 times the steady-state current. This turn-on surge presents special switch-on problems. Capacitive loads, such as fluorescent lighting, also present high-current in-rush at turn-on.