PSpice Application Notes

APPLICATION NOTE 4 + P= 3 ; Number of phases (if you change this you need ; to add more windings to the motor subckt.) + twopi = {2 * 3.141596} Cmotor shaft_speed 0 {J*twopi} ; Inertia Reddy shaft_speed 0 {1/(B*twopi)} ; Linear losses Gdrag shaft_speed ld1 VALUE = {F * V(drag) ; non-linear drag Ldummy1 ld1 0 100mH ; force timestep control Gdetent shaft_speed ld2 VALUE = {D * sin(2*A*P*V(shaft_angle))} ; detent Ldummy2 ld2 0 100mH ; force timestep control Edrag2 drag 0 TABLE {V(shaft_speed)} = (-.001, -1) (.001, 1) Rdummy1 drag 0 1 Gintegrate 0 shaft_angle_intg VALUE = {V(shaft_speed)} Cintegrate 0 shaft_angle_intg {1/twopi} IC=0.0 Rdummy2 0 shaft_angle_intg 1e12 ; (otherwise floating) Ecopy shaft_angle 0 VALUE = {V(shaft_angle_intg) ; Copy the voltage Rdummy3 shaft_angle 0 1 ; Make sure there is a load .ends Modeling the Electrical Properties Now you need to model the electrical properties of the stator windings. The properties which are required for a first order model are: Winding inductance Winding resistance Winding capacitance Winding mutual inductance Winding back EMF Torque on the rotor from the winding current The first four of these are simple electrical properties of the winding which are modeled directly by PSpice. The last two require a behavioral model. Dr. Taft et al provide the following equations for back emf and torque: V bn = C b ·S·sin ( A·θ – (N – 1)2 ߨ / P) T dn = C t ·i n ·sin(A·θ – (N – 1)2 ߨ / P) Where, V bn is the back EMF voltage for the phase n winding C b is the back emf voltage constant (volts·sec/rev) T dn is the drive torque from the phase n winding C t is the torque constant (g·cm/amp) i n is the current in the phase n winding (amp) S is the shaft speed (rev/sec) A is the number of north poles on the rotor

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