In my country, I took part in design and construction of Auto Transformer AC Voltage Regulators with automatic control of tap changing with electromechanical relays.
Since my country is less developing country in Electrical and Electronics product development, I would like to know if these Electromechanical Relay Type-Automativ AC Voltage Regulators with Auto Transformers are obselete or not.
Are they still required for certain applications?
If it is not useful anymore, I would study solid-state-relay-auto-transformer type regulators, and PWM control type, Servo motor control type AC regulator designs!
More over I would like to know how to study and analyze relay connection scheme for such regulators. ( I mean we use up to five SPDT relays to change six different tapping for auto-transformer to provide six different turn ratios, one step down, five step up between the ac input and output. I would like to study different combinations of relay contact points to provide a good voltage regulation scheme)