In three-phase applications, if low voltage is available in any one or two phases, and you want your equipment to work on normal voltage, this circuit will solve your problem. However, a proper-rating fuse needs to be used in the input lines (R, Y and B) of each phase.
The circuit provides correct voltage in the same power supply lines through relays from the other phase where correct voltage is available. Using it you can operate all your equipment even when correct voltage is available on a single phase in the building. The circuit is built around a transformer, comparator, transistor and relay. Three identical sets of this circuit, one each for three phases, are used.
The mains power supply phase R is stepped down by transformer to deliver 12V, 300 mA, which is rectified by diode D1 and filtered by capacitor C1 to produce the operating voltage for the operational amplifier (IC1).
The voltage at inverting pin 2 of operational amplifier IC1 is taken from the voltage divider circuit of resistor R1 and preset resistor. The reference voltage at non-inverting pin 3 is fixed to 5.1V through diode. The phase voltage is compared against the reference voltage and if the phase voltage is low the relay trips and shifts the load to other phase.
Q1. What is the aim of this project?
Ans1. The project aims providing correct voltage in the same power supply lines through relays from the other phase where correct voltage is available.
Q2. Why we need phase changer system?
Ans2. We need phase changer system to provide exact voltage supply to our equipments by this we can save our equipments from any voltage fluctuation.
Q3. What is transformer and on what principle it works?
Ans3. This varying magnetic field induces a varying electromotive force (EMF) or "voltage" in the secondary winding. This effect is called mutual induction.
Q4. How relay works?
Ans4. Electromagnetic attraction relays operate by virtue of an armature being attracted to the poles of an electromagnet or a plunger being drawn into a solenoid.
Q5. What is op-amp?
Ans5. An operational amplifier is a DC coupled high gain electronic voltage amplifier with a differential input and, usually a single ended output.