The main function of Resettable fuse is to do over-current protection in electrical appliances. Therefore, Resettable fuse has parameters such as voltage resistance, current resistance, maintenance current, and operating time. Therefore, it is necessary to make appropriate selection of Resettable fuse according to the voltage, current and protection current of the product used. Methods as below:

1. Determine the following parameters of the circuit:
a, the maximum working environment temperature
b, standard operating current
c, the maximum working voltage (Umax)
d, the maximum fault current (Imax)

2. Select recoverable fuse components that can adapt to the maximum ambient temperature and standard operating current of the circuit
Working temperature meter {ambient temperature (℃), working current (A)}, and select the temperature that best matches the maximum ambient temperature of the circuit. Check the value equal to or greater than the standard operating current of the circuit.

3. Compare the maximum electrical rating of the selected component with the maximum operating voltage and fault current of the circuit
Use electrical characteristics to verify in step 2. Whether the selected components will use the maximum operating voltage and fault current of the circuit.
Check the maximum operating voltage and maximum fault current of the device.
Ensure that Umax and Imax are greater than or equal to the maximum operating voltage and maximum fault current of the circuit.

4. Determining the action time of recoverable fuse
The operating time is the amount of time it takes to switch this component to a high resistance state when a fault current appears on the entire device.
In order to provide the expected protection function, it is important to clarify the working time of the recoverable fuse element.
If the component you select moves too fast, abnormal or harmful actions will occur.
If the element moves too slowly, the protected component may be damaged before the element switches to a high resistance state.
Use a typical action time curve at 25°C to determine whether the action time of the self-recovery fuse element is too fast or too slow for the circuit.
If yes, go back to step 2 and reselect spare components.

5. Verify the ambient working temperature
Ensure the minimum and maximum ambient temperature of the application. Within the operating temperature range of the recoverable fuse.
The operating temperature range of most recoverable fuse components is between -40°C and 85°C.

6. Verify the overall dimensions of the recoverable fuse element
Use the form factor table to compare the form factor of your selected recoverable fuse with the space conditions of the application.