Abstract:

As the core part of the thermal overload release of the miniature DC circuit breaker, the action characteristics of the thermal bimetal strip determine the stability of the thermal overload action of the miniature DC circuit breaker. To understand the action characteristics of the thermal bimetal strip of the miniature DC circuit breaker, taking the thermal overload release for 10 A and 16 A miniature DC circuit breakers as the research objects, a measurement method for the temperature rise, deflection and thermal thrust of the bimetallic strip is proposed. The measured values are compared with the theoretical calculated values. The measured values are slightly lower than the theoretical calculated values, and the deflection error rate is within 6.70% and the thermal thrust error rate is within 8.60%. At the same time, based on the measured temperature rise of 10 A and 16 A tests, the comprehensive heat dissipation coefficients K_T of the thermal overload release for 10 A and 16 A miniature DC circuit breakers are calculated to be 9 W/(m²·K)and 13 W/(m²·K) respectively. The accurate measurement of K_T value provides the key parameters for the theoretical calculation of the miniature DC circuit breaker.

Key words: miniature DC circuit breaker, thermal overload release, thermal bimetal strip, measurement method, comprehensive heat dissipation coefficient