Question 13.27: PSpice Analysis A DC series motor with constant K = 0.008 an...
PSpice Analysis
A DC series motor with constant K = 0.008 and K_1 = 2.5 is connected to a voltage source of 40 V. Given that the motor’s minimum and maximum speeds are 500 and 800 rpm, use PSpice to simulate and plot the power consumed by the motor if the motor’s field resistance, R_F, is 0.4 Ω and the armature resistance, R_A, is 0.2 Ω.
Based on Equation (13.24):
E_A = K \cdot K_1 \cdot \omega I_A (13.24)
E_{A}=K K_1 I_{A} \omegaThe resistance of the motor, R_{M}, can be expressed as:
\frac{E_{A}}{I_{A}}=K K_1 \omega=R_{m}Then, based on the minimum and maximum speed of 500 and 800 rpm, the minimum and maximum resistance of the motor corresponds to:
\begin{aligned}&R_{m, \min }=10 \Omega \\&R_{m, \max }=16 \Omega\end{aligned}Next, set up the PSpice schematic as shown in Figure 13.59.
To obtain the variable resistance in the PSpice circuit, go to “Part” and type “R_var.” To simulate the motor with different values of resistance in “R_var,” go to the “R_var” properties by double clicking on it. Under the value column (arrow in Figure 13.60), type “RESISTANCE” instead of inserting any integer number.
Next, another new part is introduced, which is the PARAMETERS. Here, the PARAMETERS work as global parameters which can assign a single value to multiple parts at once.
To place the PARAMETERS into the PSpice circuit, go to “Parts” and type “PARAM.” It can be found under the “Special” library. Next, go into the PARAMETERS properties menu, and set the RESISTANCE value to minimum resistance, that is 10 Ω (arrow in Figure 13.61). If the “RESISTANCE” does not appear in the properties menu, click the “New Column” (solid arrow in Figure 13.62), then type “RESISTANCE” under the NAME column. Here, the number 10 represents 10 Ω under the VALUE column (dashed arrow in Figure 13.62).
There are three types of simulations that provide the parameter sweep option, which are DC Sweep, AC Sweep, and Time Transient. Here, the circuit is DC, thus, the DC option is used. Note that AC Sweep is used for AC circuits. In addition, the Time Transient option is used if you desire to study transient analysis of the circuits (e.g., RC, RL, and RLC circuit) with different sets of parameters.
Next, set the simulation type to be DC Sweep. Under the “Primary Sweep” (solid arrow in Figure 13.63) options, set the voltage source’s name (dashed arrow) as the voltage supply in the PSpice circuit in Figure 13.63 (i.e., V1). Because the magnitude of voltage source is constant, then the start and end values of Voltage Sweep are the same (dotted arrows). Be aware that PSpice cannot run the Voltage Sweep simulation with zero increment; therefore, you must enter a number inside the increment column, such as 1.
Then, click and tick on the “Parametric Sweep” option (solid arrow in Figure 13.64). Select the “Global parameter” as the sweep variable (dashed arrow). Then, insert the parameter name that you wish to control to be swept, which is “RESISTANCE.” Enter the start and end value of the sweep as the minimum and maximum resistance obtained from calculation, with an increment of 1 (dotted arrow). Then press “Apply” and “OK.”
Run the simulation, and follow the steps as shown in Figure 13.57 to add the trace that represents the power consumed by the motor. The simulation plot is shown in Figure 13.65.
Note that the resistance of the motor is directly proportional to the angular velocity [see Equation (13.6)]. Then, you can conclude that the plot of Figure 13.65 also represents the power consumed by the motor with respect to the angular velocity of the motor.
\omega=\frac{2 \pi N}{60}=\frac{\omega_m}{60} (13.6)
