This British manufactured automatic voltage regulator forms part of the excitation system for a brushless generator. In addition to regulating the voltage it has under speed and sensing loss protection. Excitation power is derived directly from the generator terminals. Positive voltage build up from residual levels is ensured by the use of efficient semiconductors in the power circuitry. The AVR is a positive feedback control system that measures the output voltage of the generator and compares it to a set point. If there is a difference it generates a signal which in turn adjusts the excitation of the generator. This ensures the voltage is kept at a level that will not damage equipment.
Benefits of using the SX440 Stamford Automatic Voltage Regulator
The AVR is linked to both the main stator windings and the exciter field windings to form a closed loop control of the output voltage. As well as being powered from the main stator it also derives a sample voltage from the output windings for voltage control purposes. From this sample voltage the unit controls the power fed to the exciter field and hence the main field to maintain the machine output voltage within the specified limits. It will compensate for load, speed and temperature of the generator. The frequency measuring circuit continually monitors the generator output and provides under speed protection of the excitation system. A manual adjustment is provided for factory setting of the under frequency roll off point. This can easily be changed if necessary.
Technical specifications of the SX440 Stamford Automatic Voltage Regulator
Input Voltage : 190 – 264 volt ac
Frequency : 50 or 60 Hertz nominal
Single phase 2 wire
Output Voltage : Maximum of 90 volts dc at 207 volts ac input
Continuous 4 Amp dc current with intermittent 6 Amps for 10 seconds
Resistance of 15 Ohms minimum
12 watts maximum of unit power dissipation
A build up voltage of 4 Volts at the AVR terminals
Operating temperature of between -40 degrees Celsius to 70 degrees Celsius
Storage temperature of between -55 degrees Celsius to 80 degrees Celsius