Thermal Magnetic Circuit Breaker Trip Curve

The right portion of the curve is determined by the interrupting rating of the circuit breaker.

Thermal magnetic circuit breaker trip curve.

Based on 40 c ambient cold start. E t a d curve magnetic tripping characteristics vs. Connected with four 4 feet of rated wire 75 c per terminal. As a result the time current curve as shown in fig.

Circuit breaker cb 2 will trip if the overload remains for 0 200 seconds and circuit breaker cb 1 if the fault remains for 20 seconds. It is designed to react quickly to large. This is the trip curve for the coil or solenoid. The instantaneous pickup function simulates the magnetic characteristic of a thermal magnetic circuit breaker.

This is the trip curve for the bi metallic strip which is designed for slower overcurrents to allow for in rush startup as described above. The second component used in a thermal magnetic circuit breaker is a thermal bimetallic strip that responds to prolonged low level electrical surges or overloads of electrical currents. Circuit breakers cb 2 and cb 1 will continue to provide power to the circuit. 4 1 thermal magnetic trip units thermal magnetic trip units are devices which provide combined protection against overload and short circuit.

K curve magnetic tripping characteristics. This function trips the circuit breaker with no intentional time delay. Total clearing times shown include the response times of the trip unit the breaker opening and the. Here points 1 and 2 show both the thermal and magnetic action for a typical 100a mccb.

The horizontal axis on thermal magnetic trip curves shows values of available current in multiples of the circuit breaker s ampere rating from 0 5 to 100 times the rated current. Circuit breaker time current curves for application and coordination purposes only. The left portion of the curve is shown as a multiple of the long delay setting. The breaker is guaranteed to not trip before 6 seconds and will not take longer than 350 seconds to trip.

The k curve breaker will trip under a thermal overload between 6 and 350 seconds. Excessive electrical currents will heat the bimetallic strip enough to bend it towards a trip bar that turns the circuit off. Circuit breaker cb 3 is set to trip if an overload of 2000a or greater occurs for 0 080 seconds. The three major components of the trip curve are.

In circuit breakers with both short time and instantaneous pickup the instantaneous pickup will override the short time pickup if the instantaneous pickup is set at the same or lower setting than the short time pickup. Long delay pick up 115 of i. 6 combines the performance characteristics. The trip curves for electronic trip breakers are plotted like thermal magnetic trip curves except that multiples of ra ting plug or sensor amperage are labeled.

The breaker may trip at any time between 6 and 350 seconds. Types qfp vqfp 125 225 amperes 2 and 3 poles.