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 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?

 

1) step-down transformer across two phases to 5VDC power supply
2-4) Current transformer on each phase addresses all 3 concerns

 

1) step-down transformer across two phases to 5VDC power supply
2-4) Current transformer on each phase addresses all 3 concerns

Thanks, but CT on each phase will be effective when actual current flow, and that will not help to measure voltage in RYB before starting motor right?

 

1) Three phase motor don't have neutral, So how I get 5v dc to operate ESP32 using 3phase 440volt?

Actually there is a neutral point in a star wound AC motor.
I assume you mean a supplied neutral !
Your starter O/L should protect any 'Single phasing'

 

I have below starter where it has Ri-Yi-Bi as input and Ro-Yo-Bo as output to 3 phase motor, so where i get neutral here?
Please bear me with dumb question.

 

Thanks, but CT on each phase will be effective when actual current flow, and that will not help to measure voltage in RYB before starting motor right?

Poor (corroded) connection might show OK phase voltage with no load.
Shutting off power as soon as appreciable current imbalance is detected should be good enough,
provided that code does not attempt automagic restart without intervention.
FWIW, metal box with 440VAC and no ground sounds dangerous.

 

hmm, i saw almost all farmers use without earthing

 

I have below starter where it has Ri-Yi-Bi

A 7.5hp motor contactor should not be without O/L's.

 

As mentioned, transformer for low voltage supply.
unless you have more contactors, it’s not delta/wye start.
A single CT will suffice.
A pressure sw/sensor could indicate much.
Check your starter is properly sized. Current range on the O/L looks suspicious.

 

i saw almost all farmers use without earthing

Well, that should thin out the number of farmers.

 

Current range on the O/L looks suspicious.

Where is the O/L , I don't see one?
By the look of the manuf web site, none of their contactors come with O/L's??

 

Could be wrong but it looks like an adjustable current mid contactor. For a 7.5 hp motor I wouldn’t expect it to have such low numbers, so I caution the OP to check sizing.

 

I caution the OP to check sizing.

With neither conduit nor grommets protecting power wires from raw edges of ungrounded enclosure holes,
contactor sizing would be well down my priority list.

 

You really need to enlist the help of a qualified local electrician. Your lack of understanding of what you have, and hazards of the present installation are likely to cause injury or worse. I'm not criticizing you for not having knowledge of these things, just hoping to prevent you from becoming involved in potential liability.

 

Thanks,today I have studied single phase preventer and understood it better than what I knew
And i decided to use auto with spp available in market and use it to control from esp32

 

I think your last post hit it, but you can buy a Phase monitor that will cut the power to the contactor if you get a single or 2 phase loss so you don't burn up the motor. As for the other parts of your question(s), I think it's been covered some including the use of a qualified electrician for your own protection as well as the pump motor. Good luck...

 

Thank you all.

 

All that is needed is the mandatory O/L at the correct value required by NEC/CEC, if in N.A.
These generally are all that is needed in order to protect the motor

Particularly a motor of that HP!;