Hello All,
I am working on IOT based Smart Irrigation project.
In first phase I shall work on controlling water pump, right now my 7.5hp motor is controlled by "3 phase star delta starter".
Could you please provide/point to web source for following queries?
Three phase motor don't have neutral, So how I get 5v dc to operate Arduino/ESP32 using 3phase 440volt?
How to measure voltage in each phase to protect motor from phase failure?
How to measure current very accurate to protect motor from dry run? which CT is best?
Just like any other 3-phase circuit. You use a transformer on one phase to get a lower voltage. Then get a power supply that uses that voltage as input.
Again a transformer on each phase. You know the turns ratio of the transformer, so you know the voltage of the transformer secondary, which you can measure.
You can't because each of the three wires carries the current for the two adjacent phases.
Your contactor needs a separate contact set to tell you this.
Is there any other solution than using transformer on each phase, i see there are auto to automatically start motor as soon as there is power in all three phases, but that circuit not using three transformers. How to measure 440v between each phase?
Put a relay on each phase. When all three are closed, you can close the contactor and start the motor. Pretty simple.
Are you completely sure you have a DELTA configuration. What country are you in? Very few have DELTA as a standard.
If a phase fails, what ever that means, the fuse inside your mains metering box has opened and the part of the circuit is definitely open.
You need to educate yourself on how your mains power is distributed and controlled.
Ok thanks, note this approach of using relays, can we just measure voltage between RYB and detect phase is failed or not? how is this approach? whenever voltage drops below 400 we say phase failed and stop motor?
