In specific instances, where voltage fluctuation in the power supply is a frequent occurrence which causes damage to loads, a voltage stabiliser is an option.
Allow me to make it clear from the start that a voltage stabiliser can NOT replace a UPS.
A UPS generates power when the utility goes off by using battery power and converting it to Sinewave AC power with the built-in inverter, which in turn feeds the load.
A UPS also supplies the load with clean filtered Sinewave power and protects the load from switching spikes and transients on the utility supply grid.
A voltage stabiliser is an electromechanical transformer that adjusts its output for certain power input variances in voltage of up to +/- 20% while the output remains constant, but if the power fails the load goes off.
It must be remembered that a voltage stabiliser can only compensate for voltage variation to try to keep the load voltage relatively constant; it cannot generate power when the utility supply fails.
Should you require uninterrupted clean power after the utility has failed, the only option is the use of a UPS with battery backup, and a backup generator feeding its rectifier.
Upon considering a voltage stabiliser, certain selection criteria should be followed.
- 1. A top quality voltage stabiliser should supply a stable output voltage for the connected load that is unaffected by harmonic distortion on the utility supply.
- 2. A wide input voltage range is necessary to cover for voltage deviations in the utility supply.
- 3. A high-efficiency product will ensure low running cost due to low losses.
- 4. On three-phase units, each phase should operate independently as it is common that a utility supply may vary only on one of its phases. Therefore sensing on all three input phases is essential.
- 5. Modern voltage stabilisers should also be fitted with a full electronic display to allow for interrogation.