PTCR complex type thermistor Features SPMZ11 (PTC + varistor)
- PRODUCT DETAIL
WMZ13A series PTC thermistor is a protection element that automatically protects and restores abnormal temperature and abnormal current. It replaces the traditional fuse, and can be widely used for motor, transformer, electronic circuit, etc. The thermistor reduces the residual current value through its sudden change in resistance to limit the consumption in the entire line. In the traditional fuse circuit, it cannot recover by itself after being blown, and the PTC thermistor can restore its protection function after the fault is removed.
Select PTC thermistor as overload protection element. First confirm the maximum normal working current of the line (that is, the non-operating current of the PTC thermistor) and the maximum ambient temperature of the PTC thermistor installation location (during normal operation). The second is the protection current (that is, the operating current of the PTC thermistor), the maximum operating voltage, and the rated zero power resistance. At the same time, the external dimensions of the component should be considered. As shown below: Use the relationship between ambient temperature, non-operating current and operating current.
Mainly used for over-current, overload, short-circuit protection of smart meters, transformers, motors, switching power supplies, chargers, adapters, instruments, control panels, household appliances, air conditioners, microwave ovens, etc.
The over-current protection and over-voltage protection type PTC thermistor are connected in series in the power circuit. When the circuit is in a normal state, the current flowing through the PTC is less than the rated current, the PTC is in a normal state, and the resistance is small, which will not affect the normal operation of the protected circuit such as electronic equipment. When the circuit current greatly exceeds the rated current, the PTC suddenly heats up, and the resistance value suddenly increases to a high resistance state, thereby limiting or blocking the current and protecting the circuit from damage. After the current returns to normal, the PTC also automatically returns to the low-impedance state, and the circuit resumes normal work. Similarly, when the external voltage fluctuates, the varistor plays an over-voltage protection function, so that the increase in the current flowing through the PTC thermistor can also make the PTC suddenly heat up.
Transformer with composite thermistor, switching power supply overcurrent and overvoltage protection
Composite thermistor is a combination using thermal coupling,
VDR varistors and PTC thermistors are close to and packaged together. They are mainly used in power meters and other power supplies on the primary side of switching power supplies and transformers. At the same time, comprehensive protection of current and voltage is achieved. It is difficult to choose the matching with the transformer, the PTC thermistor protects the instrument from overvoltage and overcurrent conditions, and the low temperature instrument may not protect the PTC, and so on.
PTCR composite thermistor SPMZ11 (PTC + varistor) circuit diagram
When the varistor absorbs energy when the temperature rise is large, due to thermal coupling,
The temperature of the PTC thermistor will increase, plus the increase in current and heat. When the temperature reaches the PTC thermistor switch temperature, its resistance will jump.
The current decreases sharply, and its voltage drop increases a lot, the voltage across the varistor decreases, and only a small leakage current passes. Therefore, the voltage of the protected circuit is reduced to the normal working voltage range, and the power meter works normally.
Composite Thermistors commonly used models