| 摘要 |
1347409 Protective arrangements GENERAL ELECTRIC CO 15 June 1971 [23 June 1970] 27952/71 Heading H2K [Also in Divisions G1 and H1] Apparatus for measuring the temperature of a P-N junction 19 of a thyristor assembly 7, 8 (see Division H1) comprises a temperature sensor 27 mounted on a fin 21 of a heat sink and providing a first signal to an adder 41, a second signal representing current flow through the junction being supplied, from a current transformer in a sensor 22, to a function generator 39 which produces a third signal representing the power dissipated in the junction due to current flow which third signal is fed to a simulator 37 including an RC network representing the transient thermal impedance of the thyristor assembly between the junction and the mounting point of the temperature sensor, the resultant signal V 1 representing the temperature difference between the junction and the mounting point, which signal V 1 is combined with the first signal to provide a signal V 4 representing junction temperature. The signal V 4 is fed to a level detector, which for temperatures above a predetermined level actuates a gate control circuit for the thyristors of a three phase A.C. circuit breaker, or to an alarm. The temperature sensor is a P.T.C. thermistor 32 in an aperture 33 in a copper block 34 encapsulated in a mass 36 of potting material, the thermistor wires connecting to a coaxial cable 35. |
