The Secure Power knowledge base aims to give you the information you need to navigate the jargon and deliver straightforward advice around the terminology used within uninterruptible power systems.


Frequency in relation to Electrical power is the measurement of the number of cycles within a sine wave. In electricity, frequency is used to describe AC (alternating current) power, the unit of measurement is Hz (Hertz).

Frequency is predetermined, in the UK Mains power is expected to be a constant 50Hz. Equipment using this Electricity supply will need the power to stay as close to these measurements as possible to operate reliably. If the frequency increases or decreases the connected equipment will likely fail to function and could possibly be damaged as a result. 

Power Secured 50Hz

Frequency and Voltage are not directly linked, Frequency can be unstable while delivering a steady voltage, Frequency can also be stable while providing an unstable voltage.

Power Secured Voltage Dip

Each UPS has the ability to tolerate a deviation from the expected Frequency just like the Voltage input window. This can either be given as a specific min/max value or as a percentage variance of the expected 50Hz. When the input voltage moves outside of this window (or utility power fails) the UPS will be unable to draw power from the mains supply to power the connected devices, the UPS will instead use electrical power stored within the batteries to produce mains power.


Utility power isn’t always what it should be, the input of the UPS is where it is measured.

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