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For the past six months there has been increase in my electricity bill. The reason is that the maximum demand is higher (6 kW) than the sanctioned maximum demand (3 kW.)

We have a 3HP 3 phase Borewell motor. We have had the same motor for more than five years now and for the past six months it seems to be drawing 6.2 kW power instead of under 3 kW. This Borewell motor is also the only load connected to the energy meter.

Nothing has changed in the past six months except some rewiring at the energy meter (this is what I am suspecting).

The people at the electricity board are asking me to increase the sanctioned limit.

The current drawn is ~10 amperes and RYB to neutral voltage is ~230 V.

How can I troubleshoot this issue? Nobody here seems to understand that the issue is the motor drawing 6 kW while it should be drawing less than 3 kW.

Could bad wiring at energy meter cause this, or a faulty energy meter? Could the motor itself be faulty? It seems to be doing its job of pumping the water perfectly, though.

Picture 1

Picture 2

Picture 3

In the second picture, I see there's an additional red wire going into the fuse with Blue phase. I'm not sure where it is coming from.

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  • If everything is okay and working like it should, no leaks, no water log tank, then probably a partial short somewhere in the wiring. Wire insulation is broken and allowing some power to go to ground, but not enough or not getting back to the panel/breakers. This can be anywhere from the meter to the pump.
    – crip659
    Feb 24, 2023 at 13:10
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    If the load has increased then the power required will increase. Has the bore well level dropped increasing the head?
    – Solar Mike
    Feb 24, 2023 at 13:12
  • Cross Posted here: electronics.stackexchange.com/q/655331/152903
    – Solar Mike
    Feb 24, 2023 at 13:26
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    Have you measured the current yourself or is that the rated figure? Feb 24, 2023 at 13:30
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    I also wonder if a phase wire has failed. if that's a 3-phase motor, maybe one phase has gone out and the motor is limping along anyway. That wouldn't cause it to use twice the power, but it might affect your power company billing. When they provide 3 phases they want you to use it evenly. Feb 24, 2023 at 23:09

5 Answers 5

9

A stalled motor will consume a lot more current than one that is spinning freely. Check the pump for anything that could be jamming it, and check that water can flow freely through it. A clogged filter could be blocking the flow, increasing the mechanical resistance on the motor.

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My first suspicion is that it is the motor. More specifically the motor windings.

To be sure I would first isolate your energy meter. Then take separate amp and voltage readings with a quality Clamp Meter. It should be sophisticated enough to take minimum, maximum and average voltage and amperage. Cycle the motor and check each phase.

If you are getting the same reports from the clamp meter as your energy meter, then you can conclude that the insulation on the motor windings have worn down and you are getting a small amount of current passing through the windings, causing a reduction in resistance and increasing the amperage.

Depending on the cost to replace the motor or just have it rewound is a decision you will have to make.

Just remember that while you are taking these readings you will be working with energized equipment and proper PPE should be worn and shock hazard procedures need to be followed to protect yourself and others.

Hope this helps

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  • motor or the pump bearings. A motor drawing double its rated current will fail soon enough
    – Tiger Guy
    Feb 24, 2023 at 19:39
  • "that the insulation on the motor windings have worn down and you are getting a small amount of current passing through the windings" - Current taking a slightly shorter path isn't the dominant problem if that happens. A shorted turn have a far worse effect: It will act like a shorted transformer winding and cause massive losses and heating. Feb 24, 2023 at 22:12
  • Added picturess
    – Arun Gowda
    Feb 25, 2023 at 5:43
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Judging by that final photo the whole system needs to be tested for shorts to ground or between phases: the conductors are going through holes in a metal enclosure without even protective grommets let alone glands, and the insulation is already nicked through on at least the yellow phase.

Also- stating what should be obvious- does that fancy meter show the power on each phase, or if not can you get hold of a meter with a current clamp? Any imbalance would suggest a wiring or motor electrical issue, rather than the motor just working harder because the water level has dropped or there's a failing bearing.

https://www.aliexpress.com/item/1005003629905383.html

But I really would say that the workmanship shown by that final photo is utterly appalling: in short it's lethally bad and I hope you and your family don't sleep anywhere near it and are not at risk of touching that cabinet.

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Motors draw extra current when starting. a motor than runs at 0.6kW may briefly draw 6kW when starting.

To mitigate this a soft-start motor controller or a line reactor can be used to slow down the startup reducing the starting power draw. this will reduce the starting torque, but centrifugal pumps respond well to reduced torque, so this should not be a problem.

I suspect that the new meter is the cause of the increased reading, but it's likely that its not the new meter that is at fault, but rather that it was was the old meter that was less sensitive to the startup load.

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Increased current draw could also be caused by increased load on the motor. As wet end of the borehole wears it can increase friction and put more load on the motor.

This is often caused by sand getting into the wet end, due to rain and extra sand deposited into the borehole.

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  • Welcome to Home Improvement, please take the tour. Also, if you'll read through how to write a good answer, then edit your answer to explain how your suggestion could be causing the OPs problem, that would help.
    – FreeMan
    Feb 26 at 17:24
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    Welcome to the site - there's a good kernel of an answer here. Lets expand on this with an edit What could OP do to check this? Put the additional info into your answer.
    – Criggie
    Feb 27 at 9:23

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