A built-in overcurrent and overheating protector

Abstract

The invention discloses a built-in overcurrent and overheating protector, which comprises a metal shell with an opening at the bottom, a metal bottom plate for closing the opening at the bottom of the shell, and a movable contact which reverses when the set temperature is reached, and when the set temperature is lower than the set temperature. The reset thermal board, the static contact arranged correspondingly to the moving contact, the resistance heating wire and two terminal posts; the upper ends of the two terminal posts respectively pass through the bottom plate and extend into the closed space formed by the shell and the bottom plate, and the static contacts are fixed Installed on the upper end of one of the terminals, one end of the resistance heating wire is fixedly installed on the upper end of the other terminal, the other end of the resistance heating wire is fixedly connected to the bottom plate, and a mixed gas is sealed in the closed space. The resistance value is 1-220 milliohms. The mixed gas is a mixed heat transfer protection gas composed of helium and nitrogen, and the volume percentage of helium and nitrogen is 10-15% for helium and 85-90% for nitrogen. The invention has higher protection accuracy and safety performance and wider application range.

Description

technical field [0001] The invention relates to a thermal protector, in particular to a built-in overcurrent and overheating protector which can automatically cut off the power supply to prevent damage to electric equipment such as a three-phase motor and compressor when overcurrent and overheating occur. Background technique [0002] The existing built-in overcurrent and overheating protector includes a metal shell with an opening at the bottom, a metal bottom plate that closes the opening at the bottom of the shell, and a moving contact that reverses when the set temperature is reached and resets when the set temperature is lower than the set temperature. The heat-sensitive plate, the static contact arranged corresponding to the moving contact, the heater and two terminal posts; the upper ends of the two terminal posts respectively pass through the bottom plate and extend into the closed space formed by the shell and the bottom plate Inside, the shafts of the two terminal ...

AI Technical Summary

Problems solved by technology

These thermal protectors have the following disadvantages when they work: On the one hand, due to the large resistance value of the heater, the protection span of the thermal protector is too large, that is, when the overcurrent is overheated, the thermal protector will react and thus The operating temperature range for cutting off the power supply is too large, resulting in low protection accuracy; on the other hand, due to the large proportion of helium used for heat transfer in the mixed gas, the proportion of nitrogen used to prevent arc generation is small, It leads to lower safety performance; on the other hand, the power range of this kind of thermal protector matched with the compressor or motor is small, resulting in a narrow range of use of the thermal protector

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