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How are the Long Time, Short Time, Instantaneous, and Ground-fault pickup levels determined on a Micrologic trip unit?

Published date: 15 May 2020

Issue:
How to set dials on trip unit? What do the dials mean?

Product Line:
Circuit Breakers

Environment:
Applies to micrologic trip unit with Long Time, Short Time, Instantaneous, and Ground Fault on their trip unit.

Cause:
Inquires on how to set trip unit up? What the dials mean?  How are the settings determined?

Resolution:
The settings are determined by a coordination study.

Description of what the dial settings mean:

The Long Time (current rating) (Ir) is the long-time pickup setting multiplied by the sensor plug amperage (In).
The short time current (Isd) equals the short-time pickup setting multiplied by the long-time pickup (Ir).
The instantaneous current pickup amperage (Ii) is equal to the instantaneous pickup setting multiplied by the sensor plug amperage (In).
Ground fault pickup values (Ig) is equal to the ground fault pickup setting multiplied by the sensor plug amperage (In).
 

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