What is a PTC thermistor? What are the functions of PTC thermistors?

PTC thermistors can not only serve as heating elements, but also serve as "switches", including sensitive elements, heaters, and switches, known as "thermal switches". It is a thermistor with a positive temperature coefficient that increases with increasing humidity. This resistance is generally made of Barium titanate. Through different production processes and different applications, it must be made into components with unique appearance. We usually use its three characteristics of resistance temperature, voltage current and current time. The different characteristics are that different packages adapt to different places.

1. Maintain overvoltage, overcurrent, load, etc

PTC overvoltage, overcurrent, load and other maintenance applications are widely used. In PTC direct series circuits, due to circuit shorts or other reasons, PTC thermistors can suppress excessive current and even prevent components or circuits that are currently required for maintenance. Mainly used in thermal protection areas such as distribution transformers, various chargers, and various instrument equipment, it is the most common effect in PTC thermistor applications, especially in electrical equipment.

Connect PTC thermistors in series to the circuit as overcurrent protection components, that is, maintain the transformer. When the circuit is short circuited to components or loads due to various reasons, resulting in excessive current, PTC thermistors will act to prevent the circuit from generating excessive current. It should be noted that when selecting large reactive currents and operating voltages, attention should also be paid to the rated zero power resistance, operating temperature range, and component packaging. In general, during normal operation of the circuit, it is recommended to choose around 1.5 times the high working current.

2. Assist in starting motors, motors, compressors, etc

When the motor starts, it must overcome its own inertia. For example, single-phase starting requires a large torque. When the rotation is normal, the required torque is not very large. At this point, an auxiliary circuit can be added to the motor, which can be understood as an auxiliary source, equivalent to the electric vehicle having to have more power to climb a hill, and the PTC thermistor is connected in series to the auxiliary circuit.

For example, for a refrigerator compressor, if the resistance thermal resistance value increases, the power supply of the motor starting winding decreases, and the main winding of the compressor runs simultaneously. When the resistance becomes particularly high, the starting winding is equivalent to breaking, and the compressor can operate normally.

The function of PTC thermistors is not only used in switching power supplies, but also in certain levels.

3. Demagnetization applications such as color televisions and picture tubes

The function of PTC thermistors is to remove the influence of color deviation and stray magnetic fields such as geomagnetism on color images. Generally speaking, the automatic demagnetization circuit of a color TV usually consists of a demagnetization coil and a demagnetization resistor. PTC demagnetization components operate using their current time characteristics.

After the series demagnetization circuit is connected, due to the small original resistance of the PTC equipment, the coil generates a strong alternating magnetic field due to the large original current of the demagnetization coil. Due to the hot nature of PTC demagnetization components, the resistance will rise, and the current in the circuit will gradually decay, weakening the alternating magnetic field in the coil, thereby achieving demagnetization effect. This series of products is used for CRT demagnetization circuits such as color TVs and color TV displays.

In addition to the above three functions, PTC thermistors also have functions such as temperature detection and control, motor overheating maintenance, ferrochrome temperature control maintenance, tungsten wire preheating delay start, LED constant current compensation, etc. It can be used for temperature measurement and control in industry, as well as for temperature measurement and adjustment at a certain position in vehicles. It is also widely used in civil equipment, such as water temperature, air conditioning and refrigeration temperature for operating instantaneous boiling water, and its own heating is used for gas analysis and Wind turbine.

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