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General-purpose Relay: Maximum Switching Capacity

FAQ No. FAQ02763

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Question

How do you find the maximum switching capacity?

Answer

This following graph can be used to find how much current can be applied to the contacts. A description of how to interpret the graph to find out how much current can be applied at what load circuit voltage (contact voltage) is provided below.

The following figure shows how to find the maximum switching capacity for a 200-VAC inductive load.

1.Draw a vertical line where the contact voltage is 200 V (red line).

2.Draw a horizontal line from the point of intersection with the AC inductive load curve (green line).

3.Where the green line intersects the contact current axis is the maximum switching capacity. In this case, the switching capacity is 0.9 A.

Example:

To what voltage must the contact voltage be limited in order to switch a 0.5-A DC inductive load?

Answer:

Keep the voltage below 50 VDC (blue line).