Question

input voltage to the stebiliser is 220 voltsm the output voltage seen steadily as 255 volts .What part of it is not working or damaged

Answer 1

A voltage stabilizer does not have a clean sinusoidal waveform that is found straight from the power line, it is a rather lumpy looking waveform from the output and there lies the problem. Conventional voltmeters, digital or analog, are calibrated against clean waveforms and are giving an average reading. A pure, more or less , sine wave will give an average reading similar to the RMS value. When the waveform goes to hell, such as that delivered by a voltage stabilizer (constant voltage transformers are another name for these) then the only way to measure these is through the use of a true RMS voltmeter. In lieu of a true RMS voltmeter, simply hook up an appropriate wattage lamp and observe the brightness. It should be the same as the mains power compared to the output of the stabilizer. An 80 volt difference will produce a dramatic difference in brightness. If they’re the same, the issue will be with your voltmeter not being able to accurately read the distorted waveform from the stabilizer.