Over voltage and under voltage protection devices can effectively, reliably and safely realize the protection of the circuit and the power load, the reasonable, reliable and scientific design method of the over voltage and under voltage protection devices is completely possible. If we want to achieve effective, reliable and safe protection, we can not do without the following design requirements.

Design requirements for over voltage and under voltage protection devices:

1. When the line is over voltage or under voltage, automatically cut off the power line, which is the most basic function of the protector.

2. When the line voltage returns to normal, the circuit is automatically connected. This is the reason why it is called self dual over voltage protector.

3. In order to ensure that the circuit appears to be under voltage or the voltage is restored to normal, it is unnecessary to cut or connect the circuit directly. When the line is cut and connected, it has the anti time limit requirement and has the function of delay when starting or recovering.

4. To protect the reliability of the protector, the protector can work normally in the 20%~200% range of the rated voltage of the line.

5. Rated power consumption is less than 1W, the rated control current is greater than 40A.

6. In order to improve the adaptability and service life of the protector, the control contact can withstand all kinds of overload current and short short-circuit current capacity.

7. Can withstand certain lightning or inductive discharge impact transient over-voltage.

8. In order to reduce the electric arc produced by the protector, the reliability of the protector is affected. The contact line has the function of less arc in the vicinity of AC current zero crossing.

9. In order to achieve the maintenance free circuit and program should contain the relay coil fault and contact state detection function.