ACB - Air Circuit Breaker - Protection Realy Setting

#acb, #acbbreaker, #acb relay,#settings

ACB- Air Circuit Breakers:
   • ACB- Air Circuit Breakers  

1. Continuous Amps (Ir)

For example, a 1000 amp breaker can be changed from 1000 amps to 800 amps by adjusting the breaker continuous amps setting to 80%

2. Long-Time Delay

Long-time delay causes the breaker to wait a certain amount of time to allow temporary inrush currents, such as those encountered when starting a motor, to pass without tripping.

The adjustment is from 2.2 to 27 seconds at six times the continuous amps (Ir) setting.

3. Short-Time Pickup

Short-time pickup is used for selective tripping. The short-time pickup function determines the amount of current the breaker will carry for a short period of time, allowing downstream protective devices to clear short-circuits without tripping the upstream device.

Short-time pickup is adjustable from 1.5 to 10 times the trip unit ampere setting (Ir).
For example, a 1000 ampere frame can be adjusted to trip anywhere from 1500 to 10,000 amps. The switch also has an “OFF” position to eliminate short-time pickup and short-time delay.

4. Short-Time Delay

Short-time delay, used in conjunction with short-time pickup, controls the time involved in postponing a short-time pickup trip.

There are two modes: fixed time, or I2T ramp. Fixed time is adjustable from .05 to .5 seconds. The I2T ramp mode is adjustable from .18 seconds to .45 seconds, providing a short inverse time ramp.
This allows better coordination with downstream thermal-magnetic circuit breakers and fuses. A fixed instantaneous trip point of 10,000 amps trips the breaker automatically and overrides any pre-programmed instructions.

5. Instantaneous Pick up

If the continuous amp setting had been 300 amps, setting the instantaneous pickup at 10 would make the instantaneous setting equal to 3000 amps, well below the fixed instantaneous override.

6. Ground Fault Pickup

Ground fault pickup controls the amount of ground fault current that will cause the breaker to interrupt the circuit. The adjustment can be set from 20 to 70% of the maximum breaker rating. In compliance with NEC® 230-95 (A), no trip point setting exceeds 1200 amps.

The ground fault pickup is divided into three sections; .1s, .2s, and .4s. This feature adds a time delay of .1, .2, or .4 seconds to the breaker’s trip when a ground fault occurs.



(A) I2t OFF: Gives Constant time delay usually in multiplication of 0.5 sec. It has not inverse-time delay Characteristic. It is used for coordination with other circuit breakers with electronic trip devices and for coordination with thermal-magnetic circuit breakers.

(B) I2t ON :Gives an inverse-time delay that resembles the time/current characteristics of fuse It is used for coordination with fuses and upstream transformer


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