Selection of the maximum allowable capacitance (joule energy) of the power NTC thermistor.CDS sensor price

　　For a certain type of power NTC thermistor, the size of the filter capacitor that is allowed to be connected is strictly required, and this value is also related to the maximum rated voltage.

　　The power-on surge is caused by the charging of the capacitor, so the capacity of the power NTC thermistor to withstand surge current is usually evaluated by the allowable access capacitance under a given voltage value.

　　For a specific power NTC thermistor, the maximum Joule energy that can be tolerated has been determined.

　　Joule energy calculation formula of power NTC thermistor: E=(1/2)*C*(U^2)

　　It can be seen from the above formula that the allowable access capacitance value is inversely proportional to the square of the rated voltage. Simply put, the larger the input voltage, the smaller the maximum capacitance allowed to be connected, and vice versa.

　　The specifications of power NTC thermistor products generally define the maximum capacitance value that is allowed to be connected under 220VAC.

　　Assume that the maximum rated voltage of an application condition is 420VAC, and the filter capacitor value is 200μF. According to the above energy formula, it can be calculated that the equivalent capacitance value under 220VAC should be: 200×(420)2/(220)2=729μF, so when selecting the model, it is necessary to select the power with a capacitance value greater than 729μF under 220VAC Type of NTC thermistor.

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