Voltage sag or drop refers to the phenomenon that the effective value of the power supply voltage suddenly drops and then rises and recovers in a short period of time. The duration of this phenomenon in the power grid is mostly 0.5 to 1.5 seconds. The International Institute of Electrical and Electronics Engineers (IEEE) defines voltage sag as a rapid drop in the effective value of the supply voltage to 90 to 10% of the rated value, and then rises back to near the normal value; while the International Electrotechnical Commission (IEC) defines it as a drop to The rated value is 90~1, and the duration is 10ms~1min.
If the voltage sag lasts too long, it will cause the equipment to shut down abnormally. The loss of the product has been huge, and there are already relevant equipment protection devices on the market that deal with voltage sag.
The harm of voltage sag to some equipment. The impact of equipment voltage sag. Cooling controller. When the voltage is lower than 80, the controller acts to cut off the refrigeration motor, causing huge production losses. Chip tester. When the voltage When the voltage is lower than 85, the tester stops working, and the chip and motherboard are destroyed. When the voltage is lower than 81, the programmable controller stops working; some I/O equipment, when the voltage is lower than 90 and the duration is only tens of milliseconds, it will The machine tool that will be cut off is controlled by the robot to drill, cut and other precision processing of metal parts. In order to ensure product quality and safety, the working voltage threshold is generally set to 90. When the voltage is lower than this value and the duration exceeds 40~60ms When the voltage is lower than 80, the DC motor is tripped. When the voltage is lower than 70 and the duration exceeds 120ms, the ASD is cut off. For some motors in the precision processing industry, when the voltage is lower than 90 and the duration exceeds 60ms, the motor will trip and exit the operation. When the voltage is lower than 50 and the duration exceeds 20ms, the contactor will trip; Some studies have shown that when the voltage is lower than 70 or even higher, the contactor will trip the computer. When the voltage is lower than 60 and the duration exceeds 240ms, the computing work will be affected, such as data loss