All main powered devices require a supply which is
maintained within certain limits. Thus a low supply voltage can
cause malfunction, whilst a high supply voltage will cause serious
damage. Micro-processor based and other sensitive equipment requires
not only a stable voltage but a clean supply free of transient
spikes and other electrical noise.
At the heart of
an EM stabilizer, a transformer has its secondary winding
connected between the mains supply and the load, with the primary
winding voltage controlled by a motor-driven variable transformer. A
solid state servo amplifiercontinuously monitors the output voltage
of the stabilizer, and any error voltage is amplified to operate the
servo motor of the variable transformer, driving its brushgear to a
point where it is injecting a voltage that will correct the supply
voltage by adding or subtracting from it.