# Timeline for Work done pumping water with a 6 foot static head

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Mar 3, 2017 at 20:19 comment That was a great link. It covered exactly almost everything I need to know. I especially like the example motor had the highest efficiency at .31A, and the thermal wattage was 0.57. The only curiosity lurking about my motor is why the current decreases as the Work and Torque increase. Probably due to the mechanical efficiency. I did notice in the sample table of measured values, the wattage decreased around 5500 RPM. So the 0.47 is close enough for me to consider it a valid value. Negating the friction and flow loss. Great job user115350, I am not easily impressed, but I am with you.
Mar 3, 2017 at 20:06
Mar 3, 2017 at 19:48 comment The resistance measured measured is too large. Here is a link giving a full details of calculation micromo.com/technical-library/dc-motor-tutorials/…
Mar 3, 2017 at 17:50 comment Measured resistance is about 1 Mega-Ohm. The operating restive load is 40 ohm. $12.4\div 0.31$
Mar 3, 2017 at 17:20 comment What's the resistance value?
Mar 3, 2017 at 16:08 comment The pump is rated at 350 mA, 310 and 12.4 were measured and the 3.84 W was calculated from these 2 values. That black bar by the foot of the ladder is a current shunt. When the static head was zero the current was 350 mA. The wattage is inverse to work and static head. You may now see why. You say this "should be much lower" but it is the actual. The heat cannot equal VxI because the Work must be accounted for. My question is actually: Is the heat 3.84-0.47?
Mar 3, 2017 at 6:52 comment It is an interesting project. Yes, the resistance is the resistance of windings. The current might not be 0.31AMP, which is the max value. You can measure the actual current then get the actual watts $W_a=V \times I$. This should be much lower than 3.84W. The heat is $W_h=\frac{V^2}{R}$. So I guess $0.47+W_h=W_a$. Of course this misses frictional loss. With today's technology, the frictional loss is low.
Mar 3, 2017 at 6:11 comment Thank you. The resistance being the DC resistance of the motor windings? Which is different from the DC load calculated by the 12.4V / .31 Amp? I added some more photos and explanations regarding the project. Because the pumps are submersed in the water any heat generated will increase the temperature of the water. We want to find the most efficient pumps that generate the least heat per X gallons of flow. In order to evaluate the pumps, I first need to understand the problem.
Mar 3, 2017 at 1:58 history answered