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IOT based Smart Irrigation project

MrNams

Aug 28, 2021
10
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Aug 28, 2021
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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?

1) Three phase motor don't have neutral, So how I get 5v dc to operate Arduino/ESP32 using 3phase 440volt?
2) How to measure voltage in each phase to protect motor from phase failure?
3) How to measure current very accurate to protect motor from dry run? which CT is best?
4) How to get status of motor whether its on or off?
 

kellys_eye

Jun 25, 2010
6,514
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Jun 25, 2010
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6,514
1) Three phase motor don't have neutral,
1. Yes they do - in star mode they have a neutral connection.
Taking a connection from across any phase and neutral will deliver 240V - suitable for any transformer conversion to AC-DC.
2 and 3. Use a CT on each phase to measure current. No one CT is better than an other - you chose the device according to the volts/A you need for your measuring circuit.
4. How is the motor switched? Monitor the switch status?
 

Bluejets

Oct 5, 2014
6,918
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Oct 5, 2014
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6,918
"3 phase star delta starter".
As above, supply to your premesis will be in the star configuration including the neutral for access to the 240v between phase and neutral.
The fact that you have a star/delta starter is nothing to do with the supply configuration.
It is merely one of the ways to reduce starting current.
A phase failure relay(off the shelf device) will give, not only "phase failure" control but also under and over voltage control.
Dry runs are not detected using motor current, use a low pressure or loss of prime switch.
Motor status is simply a signal from the main line contactor auxiliary contacts.

Emergency stops which must be fitted ajacent to any motor will need to be direct hard wired into the main control supply.(not in any software)
Usually latter is much higher than 5v DC, typically 110v AC as the former creates control contact problems in bucket loads.

From your obvious lack of knowledge of all the above, suggest you get a qualified lecky before you electroplate either yourself or some other innocent bystander. The above is not a "diy project" type.
 
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