EE Laboratory Exercise Design Experiment Synchronous Motor Abstract: This experiment was to test the performance of a synchronous motor. One test was performed to analyze the motor under load. Another test was performed to plot the V-curves of synchronous motor. 2. Introduction: To perform the under loads test for the synchronous motor, torques should be applied to the motor, and the performance of the motor was observed. The torque was increased, and measurements of the parameters were taken until before reaching the pullout torque. Therefore, to know the expected value of the pullout torque to take measurements before that point, the pullout torque was calculated first. The following calculations are based on torque equal to 0 Nm, and field current of 0.3 A that were taken during the lab: |EfLN| = |VtLN| - Ia*(j*Xs) = 122 – (0.45 -69)* (j*150) = 63.75 V The value of armature resistor was ignored since it is very small value compare to the armature reactance. The value of armature reactance was measured in lab 7. The pullout torque happens when the power is at maximum. Therefore, the maximum power is equal to: Pmax = 3*(VtLN*EfLN)/Xs = 155.5 W. Then to find the pullout torque: Torquepullout = Pmax/w = 155.5/(1800*(2π/60)) = 0.82 N.m Moreover, the expected torque is expected to be around 0.82 for If = 0.3 A In addition, If was increased to 0.5 A and 0.7 A. Therefore, the pullout torque should be found in order to avoid reaching the pullout torque. The same steps to calculate the pullout torque was followed. For field current of 0.5 A: |Ef| = 101.08 V, Pmax = 246.64 W, Torquepullout = 1.31 Nm The second test was performed to plot the V curve for the synchronous machine by increasing and decreasing the field current and take measurements of the armature current and power factor. 3. Procedures: Performance Under Load: 1) The circuit was connected as shown in the attached wiring circuit sheet. 2) The field current was increased to 0.3 A. 3) The three-phase power supply was turned on. 4) Torque mode in the Servo was used and 0 Nm was the initial value started from. 5) The measurements of torque, speed, voltage, armature current, power factor, and input power were recorded until before the pullout torque. Then, the output power and efficiency were calculated. 6) The steps were repeated for different loads by increasing the torque by 0.1 steps. 7) The steps were repeated with field current of 0.5 A and 0.7 A. Power Factor Control: 1) Torque of 0 Nm was used and started a value of field current of 0.5 A, and field current, armature current, and power factor were measured. 2) The field current was increased and decreased to cover range of power factors. The measurements of field current, armature current, and power factor were recorded. It was noted to not decrease the field current to 0 A while applying voltage to the motor. 3) Then, torque of 0.2 Nm was applied, and the same steps were repeated as well as torque of 0.5 Nm. 4) The Servo was disengaged by pressing stop button, then the 4-pole switch and power supply were turned off as well as the isolator until after decreasing the field current to 0 A. 4. Measurements and Experimental Results: Performance Under Load: 0 0.1 0.2 0.31 0.4 0.5 0.6 0.7 pull out If Ia V 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.45 0.48 0.52 0.58 0.65 0.73 0.84 122 122 122 122 122 122 122 Pinput pf 58.5 78 97.5 117 138 162 186 0.36 0.45 0.51 0.56 0.6 0.62 0.62 speed RPM speed rad/sPout 1800 188.4 0 1800 188.4 18.84 1800 188.4 37.68 1800 188.4 58.404 1800 188.4 75.36 1800 188.4 94.2 1800 188.4 113.04 Figure 4.1 Measured parameters when If = 0.3 A Efficiecny Vs torque 70 60 50 40 n torque 30 20 10 0 0 0.1 0.2 0.3 0.4 0.5 Torque Figure 4.2 Efficiency Vs torque when If = 0.3 A 0.6 0.7 Efficiency 0 24.15385 38.64615 49.91795 54.6087 58.14815 60.77419 torque If Ia 0 0.5 0.1 0.5 0.2 0.5 0.31 0.5 0.41 0.5 0.51 0.5 0.61 0.5 0.72 0.5 0.82 0.5 0.92 0.5 1.02 0.5 1.13 0.5 1.2 is pull out torque V 0.2 0.24 0.29 0.34 0.4 0.45 0.52 0.59 0.67 0.75 0.84 0.97 122 122 122 122 122 122 122 122 122 122 122 122 Pinput pf 42.6 60.9 81 101.1 121.5 144 167.4 189 211.5 237 261 288 0.65 0.75 0.82 0.85 0.87 0.88 0.89 0.88 0.88 0.87 0.86 0.83 speed RPM speed rad/sPout 1800 188.4 0 1800 188.4 18.84 1800 188.4 37.68 1800 188.4 58.404 1800 188.4 77.244 1800 188.4 96.084 1800 188.4 114.924 1800 188.4 135.648 1800 188.4 154.488 1800 188.4 173.328 1800 188.4 192.168 1800 188.4 212.892 Figure 4.3 Measured parameters when If = 0.5 A Efficiecy Vs torque 80 70 60 n 50 40 30 20 10 0 0 0.2 0.4 0.6 0.8 1 Torque Figure 4.4 Efficiency Vs torque when If = 0.5 A 1.2 Efficiecny 0 30.93596 46.51852 57.76855 63.57531 66.725 68.65233 71.77143 73.04397 73.13418 73.62759 73.92083 torque If Ia 0 0.7 0.1 0.7 0.21 0.7 0.31 0.7 0.41 0.7 0.5 0.7 0.61 0.7 0.72 0.7 0.82 0.7 0.92 0.7 1.02 0.7 1.13 0.7 1.23 0.7 1.33 0.7 1.43 0.7 1.53 0.7 1.64 0.7 1.73 is pullout torque V 0.18 0.21 0.24 0.29 0.34 0.39 0.44 0.5 0.56 0.62 0.69 0.76 0.83 0.91 1 1.11 1.25 Pinput 122 122 122 122 122 122 122 122 122 122 122 122 122 122 122 122 122 pf 27 48 68.1 90 109.5 132 153 174 199.8 220.5 245.1 272.1 297 321 351 381 414 0.53 0.77 0.88 0.94 0.97 0.98 0.99 1 1 1 1 0.99 0.98 0.97 0.96 0.94 0.91 speed RPM speed rad/sPout 1800 188.4 0 1800 188.4 18.84 1800 188.4 39.564 1800 188.4 58.404 1800 188.4 77.244 1800 188.4 94.2 1800 188.4 114.924 1800 188.4 135.648 1800 188.4 154.488 1800 188.4 173.328 1800 188.4 192.168 1800 188.4 212.892 1800 188.4 231.732 1800 188.4 250.572 1800 188.4 269.412 1800 188.4 288.252 1800 188.4 308.976 Figure 4.5 Measured parameters when If = 0.7 A Efficiecy Vs torque 90 80 70 60 n 50 40 30 20 10 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 Torque Figure 4.6 Efficiency Vs torque when If = 0.5 A Power Factor Control: 1.6 1.8 Efficency 0 39.25 58.09692 64.89333 70.54247 71.36364 75.11373 77.95862 77.32132 78.6068 78.40392 78.24035 78.02424 78.05981 76.75556 75.65669 74.63188 torque If 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Ia pf 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.51 0.55 0.6 0.62 0.64 0.65 0.68 0.7 0.74 0.73 0.64 0.57 0.48 0.42 0.35 0.29 0.22 0.16 0.13 0.12 0.12 0.13 0.12 0.16 0.19 0.22 0.22 0.23 0.24 0.25 0.27 0.3 0.34 0.41 0.56 0.84 1 -0.93 -0.77 -0.64 -0.53 -0.4 -0.32 Figure 4.7 Measurements when torque is 0 Nm Ia Vs If 0.8 0.7 0.6 Ia 0.5 0.4 0.3 0.2 0.1 0 0 0.1 0.2 0.3 0.4 0.5 If Figure 4.8 Ia Vs If for torque 0 Nm 0.6 0.7 0.8 torque If Ia 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 pf 0.15 0.21 0.25 0.31 0.35 0.4 0.46 0.5 0.55 0.6 0.7 0.75 0.8 0.85 0.75 0.63 0.55 0.47 0.41 0.35 0.29 0.26 0.23 0.21 0.24 0.28 0.32 0.36 0.36 0.39 0.43 0.48 0.53 0.6 0.72 0.8 0.92 1 -0.83 -0.71 -0.61 -0.5 Figure 4.9 Measurements when torque is 0.2 Nm Ia Vs If 0.8 0.7 0.6 Ia 0.5 0.4 0.3 0.2 0.1 0 0 0.1 0.2 0.3 0.4 0.5 0.6 If Figure 4.10 Ia Vs If for torque 0.2 Nm 0.7 0.8 0.9 torque If 0.51 0.51 0.51 0.51 0.51 0.51 0.51 0.51 0.51 0.51 0.51 0.51 0.51 0.51 Ia 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.75 0.8 0.87 pf 0.88 0.77 0.67 0.58 0.52 0.46 0.42 0.38 0.37 0.37 0.38 0.39 0.42 0.48 0.51 0.55 0.61 0.68 0.74 0.82 0.9 0.96 0.99 1 -0.97 -0.92 -0.85 -0.76 Figure 4.11 Measurements when torque is 0.51 Nm Ia Vs If 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0 0.2 0.4 0.6 0.8 1 Figure 4.12 Ia Vs If for torque 0.51 Nm 5. Analysis and Discussion: Observing the measurements for the first test, the voltage terminal and speed are constant. The armature current, input power, and output power changes as the torque changes. The relationship between the efficiency and torque is exponential. Moreover, as the torque increases, the efficiency will increase. It was observed that as the torque increases, the power factor will be come closer to unity, then at some point it decreases again. As observed from the first experiment, as the field current increases, the pullout torque increases which allows to apply more torque until before the pullout torque. The pullout torque happens when the power is maximum. As shown in the maximum power equation, to increase the pullout torque, Ef needs to be increased since the terminal voltage and armature reactance are constants. To accomplish that, the field current must be increased since Ef is proportional to If. As observed from the data collected, the pullout torque is 0.7 Nm when the filed current is equal 0.3 A. The pullout is equal to 1.2 Nm when the field current is 0.5 A. The pullout torque is equal to 1.73 Nm when the field current is 0.7 A. Therefore, the expected values of the pullout torque are close to the measured pullout torque. Therefore, the advantage of having a higher pullout torque is that more load can be applied to the synchronous motor before reaching the pullout torque. In the second experiment, it is observed that when the field current is low, the power factor is lagging. As the field current increases, the armature current decreases and the power factor will by unity. When the field is increased more, the armature current starts to increase up again and the power factor will be leading. When the torque increases, the V curve shifts up which means the value of the armature current is higher than at 0 Nm torque. 6. Conclusion: The synchronous machine was successfully studied and analyzed. The synchronous motor was connected correctly to the testing equipment. The measurements of the pullout torque were close to the expected theoretical values. The V curve was plotted for three different loads which show that the armature current is higher as the torque increases. 7. Appendix:
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