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Old 11-06-2019, 09:32 AM   #1 (permalink)
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Join Date: May 2014
Location: Research Triangle Park
Default Half speed Loading

Since we know you are still here, Ill continue my journey... I want to examine running in the half speed region which should be full power. My quest is to find how much heat needs to be dissipated to run continually in this region. It is well known in the field that motor has a peak efficiency around 50-75% of the load but max power does not lie there. I want to see how rapidly the temperature climbs in the winding at this loading point and see if there is a way to cool the motor enough to broaden the efficiency band out to the max power point. I have no decided on what motors I want to test but the bench is under construction now. I also would like to find a good way to predict stall current with a fair level of accuracy if possible. I need this because the bench drives may no withstand the load.

Gauging temperatures by touch is never recommended, because depending on the motor, or application, proper or normal operating temperatures may be way above what could be considered safe to touch. Measuring the temperature at the surface of the motor is not a useful indicator of the temperature of the winding or bearings.

"Practical electric motors are designed for optimum cost and performance. Since they are never operated at full load in the field, they are designed for maximum efficiency around 85% of full load because that is the normal region of operation. By changing the design, highest efficiency can be made at full load. At maximum efficiency, the I^2*R losses are approximately equal to the no-load losses. At higher load, the efficiency falls again due to increase of I^2*R losses with increase of current. At 50% load, the efficiency may be typically 80% of the maximum value. It falls faster at reduced load. High-efficiency motor and custom designed motor characteristics will differ, depending on their design philosophy adopted. "

~Sujit K. Biswas
Jadavpur University~

100*C is boiling and no one can touch that or would consider it cool but the motor would operate just fine with good efficiency and is making great power.

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