Need help with 3 phase submersible motor starter

Thread Starter

Pkm28

Joined May 3, 2020
2
The submersible motor in my home works when it takes 13A on starting using a starter board. But nowadays on starting it takes 15A when turned ON and no water comes from ground. So how do I reduce the motor current from 15A to 13A. If you need some data related to starter I could provide that too.
 

LesJones

Joined Jan 8, 2017
2,639
Your description is not very clear. The starting current of induction motors is normally several time the steady state running current. I imagine the inertia of the mechanical load on the motor will be quite small so the high starting current will probably only last a few hundred mS. I am not sure is you really are talking about starting current or running current. Can you confirm what you mean ? When you say that no water comes out of the ground I assume you mean that the pump is not delivering water at it's outlet. Have you verified that the pump is actually submerged ? (I.E The water in the well has not dried up.) If the pump is submerged and not delivering water then it has probably seized up. If this is the case then I would have expected the current to have increased by a large amount.

Les.
 

Thread Starter

Pkm28

Joined May 3, 2020
2
Your description is not very clear. The starting current of induction motors is normally several time the steady state running current. I imagine the inertia of the mechanical load on the motor will be quite small so the high starting current will probably only last a few hundred mS. I am not sure is you really are talking about starting current or running current. Can you confirm what you mean ? When you say that no water comes out of the ground I assume you mean that the pump is not delivering water at it's outlet. Have you verified that the pump is actually submerged ? (I.E The water in the well has not dried up.) If the pump is submerged and not delivering water then it has probably seized up. If this is the case then I would have expected the current to have increased by a large amount.

Les.
1. I'm talking about steady state current
2. Yes, that is what I meant that water is not coming out of outlet
3. Yes, the pump is submerged into water because after starting again and again it work 1 out of 20 times
 

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LesJones

Joined Jan 8, 2017
2,639
Your pump is single phase NOT 3 phase. It is probably capacitor start capacitor run. (Or possibly just capacitor start.) These motors have two windings. The main winding and the auxiliary winding. (The main winding will have a lower resistance than the auxiliary winding.) The mains voltage is applied directly across the main winding when the contactor is latched in. The auxiliary winding is fed via a capacitor. If it is capacitor start capacitor run there wil be a lower value capacitor permanently feeding it but while the start button is held pressed there be a larger value capacitor connected in parallel with the smaller one. (If it is just capacitor start there will be no lower value capacitor.) As there are 4 capacitors in your control box they will be paralleled probably into two groups. (Or all in parallel if it is just capacitor start.) There will be two sets of NO contacts on the start button. one set will trigger the contactor on. the other set will switch in the start group of capacitors for the time this button is held pressed. On the times when it do not start I suspect the start group of capacitors is not being switched in. Can you make a note of the following for both the times when it starts and when it does not start. The current reading when the start button is being held in for about 2 seconds and the current reading when it is released. also not if the contactor remains activated after the start button is released. There looks like a lot of rust on all of the screw connections so there could be some making a poor connection. Another possibility is that some of the capacitors have gone low in value. If possible can you trace out the wiring diagram (Schematic.) as I can't follow where all the wires go and I don't know where the wires from the control box go.

Les.
 
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