The selection of pptc self-recovery fuses has always been a problem that plagues many people. So from what aspects should the selection of pptc self-recovery fuses start? What is the meaning of the parameters of pptc self-recovery fuse?
The following issues should be considered in the selection of pptc self-recovery fuses:
1. In the circuit, what is the voltage value across the series pptc element?
2. What is the average current value of the pptc component under normal circuit operation?
3. When the circuit is short-circuited to a load, how much of the fault current in the circuit will cause damage to the circuit or other components in the circuit? (That is, the maximum limit current, such as: protection circuit. When the circuit load and fault current increase to 10 amperes, the circuit or the components in the circuit are damaged, affecting the normal operation of the circuit. The pptc component is required to quickly protect the circuit. Limit current value.
4. What is the ambient temperature of the circuit? (Because the pptc element is a positive temperature coefficient thermistor, it is affected by the ambient temperature)
5. How long is the circuit working time? (Is the circuit working continuously for a long time (more than 4 hours) or intermittently)
Parameters of pptc self-recovery fuse:
Ih: Maximum working current (25 ° C), the highest current that does not trigger a resistance jump in a 25 ° C still air environment.
It: minimum operating current (25 ° C), the minimum current at which a ptc polymer resettable fuse switches from low resistance to high impedance in a 25 ° C still air environment.
Itrip: overload current, operating current.
Tmax: maximum operating time of overload current
Vmax: maximum overload voltage, the maximum working voltage of ptc polymer resettable fuse.
Imax: Maximum overload current, the maximum current that ptc polymer resettable fuse can withstand.
Pdtyp: operating power, the power consumption of the ptc polymer resettable fuse at 25 ℃ ambient temperature.
Ttrip: operating time, the maximum operating time at 5 times the holding current.
Rmin: minimum resistance at delivery (25 ℃)
Rmax: the maximum resistance when leaving the factory (25 ℃)
The above are the problems to be considered and some common parameter introduction about the selection of pptc resettable fuse.