How to choose PTC heater?
Each type of thermistor has parameters such as "withstand voltage", "withstand current", "maintain current" and "action time". You can choose according to the requirements of the specific circuit and the parameters of the product. The specific method is as follows:
1.First determine the maximum ambient temperature when the protected circuit is working normally, the operating current in the circuit, the maximum voltage that the thermistor needs to withstand after the action, and the required operating time.
2.Choosing according to the characteristics of the protected circuit or product with different shapes ptc heater such as "chip type", "radial lead type", "axial lead type" or "surface mount type".
3. According to the maximum working voltage, select the product series whose "withstand voltage" level is greater than or equal to the maximum working voltage.
4. According to the maximum ambient temperature and the working current in the circuit, select the product specification with a "maintenance current" greater than the working current.
5. Confirm that the action time of the thermistor of this specification is less than the time required by the protection circuit.
6. Check the data provided in the specification to confirm that the size of the thermistor meets the requirements.
For example, a certain control circuit needs overcurrent protection, its working voltage is 48 volts, the current is 450 mA when the circuit is working normally, and the circuit's ambient temperature is 50°C. It is required that the current in the circuit should be reduced to less than 500 mA within 2 seconds when the current in the circuit is 5 amperes.
