Problem with coil simulation

Hello everyone,

I am simulating a proposed coil model in MATLAB. The initial temperature condition for coil is 20 degrees of celsius (which is the ambient temperature). When I apply a positive triangular voltage, I expect the coil temperature to be increased (at least be more than 20 degrees of celsius in all-time of simulation beacuse 20 is the ambient temprature), while it goes down (under 20 degrees of celsius). When I apply a three times larger voltage, the temperature trend goes well, and it never goes under 20, but I need to apply a low voltage for my simulation.

Here is the equations:

According to my understanding, i^2R should have a large enough value so that the temperature does not drop below its initial value.

Any help would be appreciated.

[Torsten]

We don't know your code and the parameter values you chose.

If the result is as shown, the temperature increase by the term i^2*R is overcompensated by the heat loss to the environment.

[David Goodmanson]

Hello M^2,

SInce you don't show any code it is only possible to speculate. However, the first equation has two terms. If Cth, R(s,T) and lambda are all positive, then the first term raises the temperature, and the second term provides relaxation back to ambient temperature. So if you start at ambient temperature, T cannot fall below ambient. One possibilty (implied by the plot) is that R(s,T) is actually negative at t=0, which you can check.

Answer 1

[M.M]

Thank you @Torsten and @David Goodmanson. My problem has been solved; It was a mistake to implement my nonlinear model. Thank you for the points you mentioned!