Differentiation, Minima and Maxima

I want to differentiate the following loop for an induction motor with respect to (s) and find the minima and maxima:

for ii = 1:51
    t_ind1(ii) = (3 * v_th^2 * r2 / s(ii)) / ...
            (w_sync * ((r_th + r2/s(ii))^2 + (x_th + x2)^2) );
end

Which is the best method/approach to achieve this?

Frank

[Basil C.]

I guess this equation for calculating the Torque produced by an induction motor where s is the slip percentage. But why are you using s(ii), is it an array? If so, then how do you plan on differentiating it??

Answer 1

[Walter Roberson]

[max_t_ind1, idx_max_t_ind1] = max(t_ind1);
[min_t_ind1, idx_min_t_ind1] = min(t_ind1);
s_max_t_ind1 = s(idx_max_t_ind1);
s_min_t_ind1 = s(idx_min_t_ind1);

Assuming, that is, that there is only one minimum and one maximum. If there could be multiple, either use findpeaks() or else look for sign changes in diff(t_ind1)

[Frank Lehmann]

Thanks Walter, it works like a charm!!