Computer analysis of the differential equation of the model of the synchronous electric motor that does not include electric currents

Phase portraits of the well-known equation of the no-current model of the synchronous electric motor are obtained with use of computer, and some properties of its solutions are noted, which are imperceptible at the phase portraits, obtained analytically. With use of computer, a graph is built for the curve, representing the critical value versus the principal stationary value of the angular variable. Linear and sinusoidal approximations are proposed for this curve, maximum absolute and relative errors of these approximations are calculated.