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General-purpose Relay: Switching Capacity Varies

FAQ No. FAQ02771

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Question

Why do Relays switching capacity vary with the type of load?

Answer

Generally, the switching capacity for an inductive load will be lower than the switching capacity for a resistive load due to the influence of the electromagnetic energy stored in the inductive load.

Example: MY2 General-purpose Relays

Resistive loadInductive load (cos Φ = 0.4, L/R = 7 ms)
Rated load220 VAC, 5 A
24 VDC, 5 A
220 VAC, 2 A
24 VDC, 2 A

When AC inductive loads are used, an inrush current of 5 to 10 times (varies with load) the steady-state current will be generated.
For DC inductive loads, 5 to 10 times (varies with load) the counter electromotive force is generated.
Allow for a margin when selecting Relays.