APPLICATION NOTE
8
Figure 2: Simulation Results
In Figure 2, the top plot shows the motor torque delivered by the phase 2 stator winding. The middle plot
shows the back EMF voltage for the phase 2 winding. Notice that as the motor speed increases, the back
EMF increases and the torque decreases. The bottom trace shows the motor shaft speed (1volt =
1rev/sec) and the motor shaft angle (1volt = 1radian). The shaft angle has been normalized to
the range from -ߨ to +ߨ by the Probe macro Norm_Angle. The Norm_Angle macro is defined as:
Norm_Angle(a) = 2 · atan(sin(a/2))/cos(a/2))
Note: If the shaft angle is not normalized to the range from -ߨ to +ߨ, the shaft angle increases by 2ߨ for
each revolution.
A Brushless DC motor is a relatively complex electromechanical system to simulate in detail. But PSpice's
Analog Behavioral Modeling feature allows you to model it in enough detail to verify the operation of an
electronic motor control system.
Tip: The model described is included in the Model Library, misc.lib.
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