Load Types & Ratings

Applications

Load Types & Ratings

Inrush current is a current that is much larger than the steady-state current and that flows as soon as power is input to the electric circuits that operate the load.
Inrush current occurs for loads such as motors and incandescent lamps.

1. Inrush Current

  • Resistive Loads

    The current is constant from the time that power is turned ON.
  • Lamp Loads

    Inrush current of approximately 10 times the steady-state current flows as soon as power is turned ON and then the current becomes constant.

2. Inrush Current and Ratings

If ratings are given for both motor loads and lamp loads, switch applicability is determined with the relevant value.
If the rating is given only for a resistive load, the inrush current for the actual load is calculated to determine if the rating would be exceeded.

Examples:
Heater: A resistive load. The steady-state current must be less than the resistive load rating.
Incandescent lamp: A lamp load. Ten times the steady-state current must be less than the resistive load rating.
Motor: A motor load. Six times the steady-state current must be less than the resistive load rating.

Include the inrush current when you consider ratings.