热敏电阻电机保护是利用热敏电阻对温度的敏感性,直接反应电机绕组温升,使其不超过极限值的一种电机保护装置,解决了热继电器和被保护电机不易配合得好的矛盾。此装置具有线路简单,保护全面、可靠等优点。半导体热敏电阻是热敏感半导体材料制成的一种非线性电阻元件,其电阻值随温度的变化而变化。阻值随温度的升高而增加的称正温型热敏电阻,反之称负温型热敏电阻。还有一种热敏电阻当温度升高到某一数值时其阻值急剧增大,叫正温开关型热敏电阻。电路由整流稳压电源,二极管门电路和射极偶合触发电路组成(见附图),PT为热敏电阻,我们采用正温型。裹在电机三相绕组中,直接反映绕组温升。 Thermistor motor protection is the use of thermistor sensitivity to temperature, a direct response to motor winding temperature rise, so that it does not exceed the limit of a motor protection device to solve the thermal relay and the motor is not easy to be well with the coordination of the contradiction . This device has the advantages of simple circuit, comprehensive protection and reliability. Semiconductor thermistor is a non-linear resistance element made of heat-sensitive semiconductor materials, the resistance value of which varies with temperature. Resistance increases with the temperature increases and said positive temperature type thermistor, conversely, said negative temperature type thermistor. There is also a thermistor when the temperature rises to a certain value of its resistance increased dramatically, called the positive temperature switch type thermistor. The circuit consists of rectified power supply, diode gate and emitter coupling trigger circuit (see photo), PT for the thermistor, we use the positive temperature type. Wrapped in the three-phase motor windings, directly reflects the winding temperature rise.