Simulate open circuit and short circuit in MATLAB

[Fatima Hasan]

Homework Statement

Written below.

Relevant Equations

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Here's my attempt:

The results I got are close to the required answer, but there is a question telling:

I tried to solve it, but Isc and Vt (in open circuit) are decreasing with the increase of the field current , so I didn't get the right answer. Could someone let me know where is my mistake ?
Here's the machine parameters :

 

[Valkarie]

Ra = 0.2ohmX1 = 4ohmX2 = 2ohmXm = 3ohmYour mistake is in the way you calculated the Isc and Vt values. Instead of using the field current as a parameter to calculate these values, you should use the open-circuit voltage (Voc) as the parameter. The Isc and Vt values are determined by the machine parameters and the Voc. For example, if the Voc is 10V, then the Isc will be equal to the Voc divided by the sum of the Ra and X1 values (10V/6ohm=1.67A). Similarly, the Vt can be calculated as the Voc multiplied by the Xm value (10V*3ohm=30V). Therefore, when calculating the Isc and Vt values, you should use the same Voc value for each calculation. This way, you will get the correct results.