NTC three-phase asynchronous motor protection circuit a

Semiconductor thermistors are embedded thermal protection components and are very sensitive to temperature. The temperature control error is ±5°C. It has high reliability
, small size (diameter is 3. Smm), easy installation, and easy to embed in the winding. Using it as a temperature sensing element can effectively reflect
the temperature of the motor winding. The thermistor is placed in the three-phase stator winding, close to the enameled wire, and fixed with epoxy resin. Thermistors
are divided into negative temperature coefficient thermistors ( NTC ) and positive temperature coefficient thermistors (PTC).
    The circuit is shown in Figure 4-1. Figure 4-1 (b) and (c) only show the protection circuit and not the main circuit. They are both
a switching circuit consisting of a single tube amplifier.
    Thermistor brother. ,R. . ,R. , you can choose RRC6 type or MF-15 type (lokfl, 20℃). This thermistor
is about lkfl at 100℃ and about 0.6k, Cl at 110℃.