OPERATION

BE3-37 and BE3-51 ac current relays have two external, user

adjustable controls marked SET and DELAY. The BE3-37/51 has

four controls: UNDER SET, UNDER DELAY, OVER SET, and

OVER DELAY. The SET control adjusts the relay trip point. An

overcurrent trip causes the relay output to energize when the

current rises above the SET threshold. The overcurrent SET level is

adjustable from 40 to 120% (±3%) of nominal input. An undercurrent

trip causes the relay output to de-energize when the current

decreases below the SET threshold. The undercurrent SET level is

adjustable from 0 to 80% (±3%) of nominal input. Time delay is the

amount of time that elapses after the trip point is reached and when

the output relay operates.

Setting Example

A BE3-51 relay has the following settings:

SET – 120%

DELAY – 4 seconds

A trip occurs when the sensing current rises above six amperes for

four seconds. Reset occurs when the current decreases below 5.75

amperes (5% of nominal below trip setting).