AUTOMATIC PHASE CHANGER PROJECT
101％ working project hello friends today I am gonna telling you about some easy and valuable electronics projects for school and college practical
Today I have brought you a circuit that will not allow your work to stop, if your three face machine and the voltage of one face is reduced or it breaks down then it helps you and changes the face in an automatic way.
However, there is a need to use an appropriate rating fuse in the input lines (R, Y and B) of each stage. The circuit provides the correct voltage through the relay from the second stage to the same power sup ply lines where the correct voltage is enabled. Using this, you can operate all your devices even when the correct voltage is available in single phase.
The circuit is built around a transformer, comparator, transistor and relay. Three identical sets of this circuit, one each for three phases, are used. Let us now consider the work of the circuit connecting the red cable (this is called the 'R' phase).
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| Fig1; circuit Diagram |
The mains power supply phase R is stepped down by transformer X1 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 VR1. VR1 is used to set the reference voltage according to the requirement. The reference voltage at non-inverting pin 3 is fixed to 5.1V through zener diode ZD1.
Till the supply voltage available in phase R is in the range of 200V - 230V, the voltage at inverting pin 2 of IC1 remains high, i.e. , more than reference voltage of 5.1V, and its output pin 6 also remains high. As a result, transistor T1 does not conduct, relay RL1 remains de animate and phase 'R' supplies power to load L1 via normally closed (N / C) contact of relay RL1.
As soon as phase - R voltage goes below 200V, the voltage at inverting pin 2 of IC1 goes below reference voltage of 5.1V, and its output goes low. As a result, transistor T1 conducts and relay RL1 energises and load L1 is disconnected from phase 'R' and connected to phase 'Y' through relay RL2.
Similarly, the auto phase - change of the remaining two phases, viz, phase 'Y' and phase 'B' can be explained. Switch S1 is mains power on or off switch.
Use relay contacts of proper rating and fuses should be able to take - on the load when transferred from other phases. While wiring, assembly and installation of the circuit, make sure that you:
1. Use good - quality, multi - strand insulated copper wire suitable for your current requirement
2. Use good - quality relays with proper contact and current rating.
3. Mount the transformer (s) and relays on a suitable cabinet. Use a Tag Block (TB) for incoming / outgoing connections from mains.
Note: During testing in the lab, we used a 12V, 200 - ohm, single phase changeover relay with 6A. Similarly, ampere-rated fuses were used. If the input voltage is low in two stages, the load L1 and L2 may also be connected to the third stage. In that case, a fuse with a higher rating would be required on the third stage input which is carrying the total load.
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