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ITGlossary · Power quality
Voltage Drop
A decrease in voltage level in a circuit due to resistance or high load.
Technical level:Basic
Every cable has a small resistance, so when current flows through it part of the voltage is lost along its length. The longer and thinner the cable and the higher the current, the greater the voltage drop. It often shows up in remote buildings, at the end of long lines or at peak hours when many consumers are running at once.
Low input voltage can make a UPS switch to battery frequently, wear the batteries out prematurely or affect motors and air conditioners. An AVR stabilizer or a UPS with a wide input voltage range copes with such conditions.
During installation, choose the cable cross-section based not only on the current but also on the length, especially for the lines feeding the UPS and the DC battery cables.
Related terms
- UndervoltageA sustained drop of mains voltage below normal that can cause malfunctions or overheat motors.
- Voltage SpikeA momentary, very high voltage rise lasting microseconds, e.g. from lightning or load switching, that can damage equipment.
- Automatic Voltage Regulator (AVR)A device that automatically maintains a constant voltage level to protect electrical equipment from fluctuations.
- Input Voltage WindowThe range of mains voltage within which a UPS keeps powering the load from the grid without switching to battery.
- Noise (Electrical)Unwanted high-frequency disturbances on the supply voltage, e.g. from motors or power supplies, which UPS systems and line conditioners filter out.
- Power ConditioningTechniques such as EMI/RFI filtering, surge protection and AVR that correct voltage problems before they reach the load.