An uninterrupted power supply is used to prevent total power failure to computers during a power failure or power fluctuations.

A UPS provides temporary power in the event of a power failure.

The UPS provides 5 to 10 minutes of backup power while an alternative power source, such as a generator, is switched on.

A UPS is good as additional protection against damage from electrical spikes or dips.

An inverter is recommended to get more time from battery backup!

A voltage regulator  stabilizes voltages from an unstable source, such as a petrol or diesel generator.

It should  be noted that a Voltage regulator will not correct frequency problems.

UPS keeps switching on and off while using a generator

UPS are sensitive to the voltage and frequency on its input - this is the way it detects whether it should switch to battery backup mode or not. This is normal operation for a UPS.

Cheaper generators, such as those used by home owners, are not always calibrated accurately for frequency (50Hz in South Africa), even if the voltage is within an acceptable range.

If the frequency is border-line, the UPS tends to switch over to battery mode whenever it goes out of the UPS's acceptable frequency range, and then switches back to off-line mode when it is in range again. This may cause the UPS to continuously switch over.

The way to correct this behaviour is to set the throttle on the generator to a point where the UPS becomes stable. This can be done by tweaking the throttle screw slowly in either direction.

It should be noted that a Voltage regulator / AVR will not correct the frequency.

An AVR will only correct voltage fluctuations. An AVR will protect sensitive equipment from Voltage dips and spikes.

Examples where an AVR is helpful includes: