Solar pump soft stopping

[Brenbert]

We have a Powtran PI500-S Solar Inverter driving a 15hp 3phase water pump at between 100 and

130 feet of head. The inverter has its own MPPT and we are running solar panels only - no

batteries. The only problem is that when clouds cover the sky rather rapidly the pump stops

abruptly. There is a spring loaded check valve on the pump that prevents any water hammer but it

seems to me that would should be able to program the inverter to slow down and stop the pump

if it could sense the voltage drop caused by clouds. How much of a voltage drop does cloud

cover cause and how much time would we have to soft stop the pump? I have practically no

experience with solar panels yet. Can anyone tell me if this would even seem feasible?

 

[snoobler]

Welcome to the forum.

When clouds cover the panels rather rapidly, power drops off very rapidly. Cloud cover may cause little to no voltage drop, and MPPT may have voltage all over the place while searching for max power point. Current is what drops fast.

 

[MisterSandals]

seems to me that would should be able to program the inverter to slow down and stop the pump

Do you suspect that an an abrupt power cut has a negative impact on the motor or pump?
My understanding of well pumps is that they are designed for full-on or off. Ramping down the power, from what i can imagine, would be harder on the motor windings if it were working hard.

 

[Brenbert]

Do you suspect that an an abrupt power cut has a negative impact on the motor or pump?
My understanding of well pumps is that they are designed for full-on or off. Ramping down the power, from what i can imagine, would be harder on the motor windings if it were working hard.

Thank you for the answer. I was more worried about the stress on the rest of the system: pipes , connections, etc. but my friend who is building this system for irrigation purposes assures me there is no water hammer when the pump stops. As for the motor winding, I am not too worried about ramping down motors as long as you do not hold the rpm low for a period of time because you are limiting the cooling effect of the fan or cooling impeller.

 

[Brenbert]

Do you suspect that an an abrupt power cut has a negative impact on the motor or pump?
My understanding of well pumps is that they are designed for full-on or off. Ramping down the power, from what i can imagine, would be harder on the motor windings if it were working hard.

Welcome to the forum.

When clouds cover the panels rather rapidly, power drops off very rapidly. Cloud cover may cause little to no voltage drop, and MPPT may have voltage all over the place while searching for max power point. Current is what drops fast.

Thank you for the welcome and you comment. I agree that there would be no voltage drop on the output of the MPPT but since we use as many panels as we can to boost the power (Voltage x Amps) at the input of the MPPT, I still wonder if there would not be a way of detecting a coming shutdown. But if the drop in power is that drastic we will just have to leave well enough alone.

 

[snoobler]

When you can predict shading, you can get what you want.