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How to test the Overload relay using Current injection kit for LRD350

The Tesys LRD series reference LRD is a Thermal Overload Relays, which does not have any separate testing procedure available. You have to follow the same procedure of testing specified in IEC 60947-4-1 applicable for all thermal overload relays.

The LRD relays are thermal overload relays which work on the Inverse thermal principle and follow the Tripping curves ( as published in the catalog or instruction sheet) when subjected to the Overload .

These Tripping curves are in accordance with the IEC 60947-4-1 which define the Tripping test point of the LRD as under :

- 1.2 x In and at this value your product should trip in less than 2 hours.
- 7.2 x In and the LRD (class 10A product ) should trip within 2 to 10 seconds.
Where , In = Current Setting

For example, it is normal for the product not to trip at 50A if you set it a 48A, as the tripping threshold will begin around 54.7 A ( 1.14In +/- 0.6) and before this the system may continue to work without tripping at all.
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