PTC thermistor is a kind of positive temperature coefficient thermistor, and the resistance increases with the increase of temperature. Such resistors are usually made of titanium rods. Due to different production processes, different applications need to obtain special shaped components. We usually use three characteristics: resistance temperature, voltage current and current time. Different functions are rooted in different packaging to adapt to different occasions.

1. Overvoltage, overcurrent and overload protection

PTC overvoltage, overcurrent and overload protection are widely used. In PTC direct series circuit, current is caused by short circuit or other reasons. PTC thermistor can damp excessive current and even prevent current protection required by components or circuits. It is mainly used in power transformer, various chargers, various instruments and meters and other over-current thermal protection occasions. This is a commonly used PTC thermistor function, and we have seen more, especially in power equipment.

PTC thermostat is connected in series to the circuit as an overcurrent protection element to protect the transformer. When the circuit is short circuited or loaded due to various reasons, resulting in excessive current, the PTC thermistor will prevent the circuit from generating excessive current during this period. It should be noted that the rated zero power resistance, operating temperature range and package of components should also be considered when selecting large passive current and operating voltage.

2. Engine, engine, compressor and other starting AIDS

Inertia must be overcome when the engine is started. For example, single-phase starting requires high torque. When the rotation is normal, the required torque is not too high. During this period, you can add an auxiliary circuit to the motor, which can be understood as an auxiliary power supply, which is equivalent to that the electric vehicle needs more power for climbing, and the PTC thermistor is connected in series to the auxiliary circuit.

For example, in the case of a refrigerator compressor, when starting, the thermal resistance value becomes large, the starting winding of the compressor motor is connected, and the main winding of the compressor works at the same time. When the resistance becomes large, the starting winding is disconnected and the compressor can work normally.

PTC thermistor function is not only used for power switch, but also applied in many aspects.

3. Degassing application, such as color TV and image lamp

The function of PTC thermistor is to eliminate the influence of non drop magnetic field (such as color difference and geomagnetism) on color images. The automatic quenching circuit of ordinary color TV is composed of quenching coil and quenching resistor. The PTC degaussing element has a current time characteristic.

After the quenching circuit is connected in series, the initial resistance of PTC element is small, and the initial current through the quenching coil is large, so that the coil generates a strong variable magnetic field. Due to self heating, the resistance of PTC demagnetization element will increase, and the current in the circuit will gradually decompose. Therefore, the variable magnetic field in the coil will also weaken to achieve the demagnetization target. This series of products are used for degassing circuits of color TV sets, color TV displays and other cathode ray tubes.