Laboratory Implementation of Automatic Voltage Regulator

The terminal voltage of an alternator delivering power to an isolated load will vary depending on power and power factor of the load. All loads are to be supplied power at a specified voltage within some tolerance, which depends on application. The tolerance of the alternator can be maintained within this range by suitably controlling the excitation of field winding. Automatic adjustment of excitation is made by Automatic Voltage Regulator (AVR) which senses the terminal voltage of alternator and compares it with a reference voltage and generates an error signal which in turn adjusts field current. In this paper, an AVR is designed for a laboratory alternator of 5 kVA power rating. Electromotive Force test (EMF) and Zero Power Factor (ZPF) tests are conducted on the alternator to determine the minimum and maximum field current. A triggering circuit is designed for the fully controlled thyristor bridge converter which supplies current to the field of the alternator. An analog feedback circuit is fabricated and tested to automatically control the output voltage of the alternator. The entire hardware setup is tested on the alternator for various loading conditions.