Relay Type or Tap Changing AC Voltage Stabilizer
Block Diagram of Tap Changing AC Voltage Stabilizer :
The block diagram of the tap changing regulator is as shown in figure.
Operation of Tap Changing AC Voltage Stabilizer :
- As shown in Fig . 5.161, the primary winding of the transformer is divided into several taps. One end (A) of the transformer is connected to the neutral (N) point of the ac supply, whereas the live terminal is connected to one of these taps through a relay N.O. (normally open) contact.
- The sensing circuit senses the input voltage and selects one relay out of the three for conduction. For example, if the input voltage is 260 Volts then relay 3 will be energised, this will close the normally open contact N.O.3 and the secondary voltage will be reduced.
- If the input voltage is normal le say 230 Volts, then only relay 2 is energised, NO.2 is closed and the secondary voltage is again maintained within a prescribed range.
- If the number of taps is increased, the output voltage regulation also will improve. However it adds to the cost of the circuit.
Disadvantages of tap changing regulators :
- The voltage correction is in steps. So the voltage regulation is poor.
- The dynamic response is poor, i.e. the time taken by the regulator to correct the voltage is long due to the use of relays.
- Due to the use of transformer, the efficiency is low, about 70%.
Applications of Tap Changing AC Voltage Stabilizer :
Refrigerators, T.V. etc.
Advantages of Tap Changing AC Voltage Stabilizer :
- Simple circuit
- Cost effectiveness