A voltage stabilizer is a power device destined to be positioned between the mains and the User. The purpose is to ensure that the User is fed a voltage subject to a variation much lower (±0.5% with regards to the nominal value) than the one guaranteed by the distributing system. The following mainly introduces the design principle of the voltage stabilizer.
The stabilization is performed on the “true RMS” voltage and it is not affected by harmonics in the mains. Due to the fact that the regulation does not involve any intervention on the sinewave, neither an appreciable harmonic distortion nor a phase displacement is introduced on the downstream line. The voltage stabilizer is not affected by the load power factor (cos φ) and can operate with a load percentage varying between 0% and 100% on each phase. Regulation speed depends on the input voltage variation percentage and on the type of construction. Indicatively, said speed ranges between 8 and 30millisec/V.
Basically, a voltage stabilizer is made of a buck/boost transformer, a voltage regulator, and electronic control. Based on a microprocessor that samples at high frequency the output voltage, the control system drives the regulator gearmotor. By doing so, the regulator rollers change their position, and therefore the voltage is drawn and supplied to the buck/boost transformer primary winding. Being the secondary voltage of the buck/boost transformer in phase or in opposition to the supply, the voltage is drawn from the regulator is added or subtracted to the mains voltage, thus compensating its variations.
The voltage stabilizer is nothing but an autotransformer with a continuously variable transformer ratio. Depending on the stabilizer power, the regulator can be either toroidal or columnar.
The stabilizers are designed and built-in in compliance with the European Directives concerning CE marking (Low Voltage and Electromagnetic Compatibility Directives). Standard units are housed in an IP21 metallic enclosure RAL7035 painted. Cooling is guaranteed by natural air circulation aided by extracting fans over a certain temperature. The voltage stabilizer operating nominal voltage can be chosen from values (generally included in the range 380V / 415V). Such a setting can be performed at the factory or at the customer’s premises according to the instructions given in the reference technical handbook.