Rotational speed in DC machine

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    Dc Rotational Speed
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Discussion Overview

The discussion revolves around the calculations related to rotational speed in a DC machine, specifically focusing on the relationship between excitation voltage (Vexc), torque, and rotational speed. The context appears to be problem-solving related to an exercise involving these parameters.

Discussion Character

  • Homework-related, Technical explanation

Main Points Raised

  • One participant requests the calculations to verify the approach taken in solving the problem.
  • Another participant acknowledges a previous error in their approach, noting that they needed to calculate the torque constant (Kt) as it varies with excitation voltage (Vexc) before determining the new rotational speed while keeping torque constant.

Areas of Agreement / Disagreement

The discussion does not present a consensus, as one participant is seeking verification of calculations while another reflects on their own correction of approach.

Contextual Notes

There may be limitations related to the assumptions made about the relationship between torque, Kt, and rotational speed, which are not fully detailed in the discussion.

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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Welcome to PF.

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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