Engineering Rotational speed in DC machine

AI Thread Summary
Calculations for rotational speed in DC machines require determining the torque constant (Kt), which varies with the excitation voltage (Vexc). The correct approach involves first calculating Kt before using it to find the new rotational speed while keeping torque constant. The initial misunderstanding stemmed from not accounting for the variable nature of Kt. Accurate calculations are essential for understanding the relationship between torque and rotational speed in DC machines. Proper methodology ensures correct results in these exercises.
paola21
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Homework Statement
rotational speed in DC machine
Relevant Equations
I tried to do the last point but I can't find the result. I calculated, knowing the new value of Vexc, the new value of Iexc and from this the new value of the flux. then with the inverse formula of the twisting torque I obtained the new speed which however comes out about 1920 rpm
I don't understand where I went wrong
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Can you show your calculations so that we can check them? Thanks.
 
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I solved the exercise, I had the wrong approach. I had to first calculate Kt which varies with Vexc and then from this new value of Kt, knowing that the torque remains the same, calculate the new rotation speed. Thanks anyway
 

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