class: center, middle # EE-362 ELECTROMECHANICAL ENERGY CONVERSION-II # Recitation Hour ## Ozan Keysan [ozan.keysan.me](http://ozan.keysan.me) Office: C-113
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Tel: 210 7586 --- # Induction Motors --- # Ex 1: Yildirim Uctug-Solved Problems CH2-Q17 --- ### A 380 V(l-l) 3-phase 4-pole Y-connected induction motor's torque-speed characteristics can be approximated as: -- ## \\(T\_m = k s = \dfrac{3 V^2}{r'\_2 \omega\_s} s\\) -- ### where \\(r'\_2 = 1 \Omega\\)/phase. The motor is used to drive a load at a precisely constant speed of 1500 rpm. -- The load torque can be expressed as: ### \\(T_L=\omega_r + 10 \\) Nm. --- ## a) Propose a method of speed control for this purpose and explain your reasoning, and calculate the required controller parameters. -- ## b) Calculate the operating slip of the motor. -- ## c) Give a rough estimate for the efficiency of the motor under these conditions. -- ## d) What is the minimum value of starting torque the motor must produce? --- # Induction Motors --- # Ex 1: EE362- Year 2004 MT2:Q3 -- ### A 3-phase, 4-pole, Y-connected, 208 V (line), 50 Hz induction motor is run under no-load conditions and the following data are obtained: -- ### \\(I\_1 = 1.562 A\\) ### \\(P\_{in} = 432 W\\) -- ### a1) Find core loss resistance(\\(R\_c\\)) and magnetizing impedance (\\(X\_m\\)) --- ### Now, the motor is run under 8.73 Nm load, and it is found that it draws 5.5 A 0.944 pf lagging, and the slip is measured as s=0.05. The stator phase ac resistance is measured as \\(1.2 \Omega\\) -- ### a2) Find the other parameters of the equivalent circuit #### Note: Assume the shunt branch is moved to supply terminals, and assume x1=x2' --- ### Now, assume the motor is driven by an inverter that can produce an output voltage in the range of 0-208 V (line-to-line). The frequency can be controlled in the range of 0-200 Hz. It is desired to run this motor at 150 Hz. -- ### b) Calculate the terminal voltage required to keep the pole flux constant at the rated value. --- ### Now, assume the motor is driven by an inverter that can produce an output voltage in the range of 0-208 V (line-to-line). The frequency can be controlled in the range of 0-200 Hz. It is desired to run this motor at 150 Hz. ### c) Is the inverter capable of running the motor at the voltage level in part (b)? Otherwise suggest and operating mode and calculate the operating flux per pole as a ratio of the rated flux. --- ### Now, assume the motor is driven by an inverter that can produce an output voltage in the range of 0-208 V (line-to-line). The frequency can be controlled in the range of 0-200 Hz. It is desired to run this motor at 150 Hz. ### d) Calculate the torque output of the motor at a slip of 0.0.5. --- # Q2: Ahmet Rumeli Solved Problems: Q6.5 ### A 6-pole, \\(215 \sqrt{3}\\), Y-connected, 60 Hz wound rotor induction motor has the following specifications -- ### Stator impedance: \\(Z\_1 = 0.2 + j0.38 \Omega\\) ### Referred Rotor impedance: \\(Z\_2' = 0.12 + j0.38 \Omega\\) at standstill ### The motor is used as a crane motor, which lifts and lowers a load that produces 160 Nm. #### Neglect friction. Parallel branch moved to primary terminals --- ### a) While lifting the load at constant speed, find the stable operating slip? -- ### a2) What is the slip at maximum torque? -- ### b) While lifting the load at constant speed, the supply voltage is cut and the load is left to move freely. What happens if the rated voltage is reapplied at slip: -- ### b1) Less than 1.244? -- ### b2) Greater than 1.244? What is the type of operation in this case? --- ### c) What is the minimum lifting speed which can be achieved by reducing the applied voltage? Find the voltage and the corresponding speed. -- ### d) With this new voltage, if you need to reduce the speed down to 600 rpm. What should be the value of the external resistance that is connected in series with the rotor resistance? --- # Synchronous Machines -- ## Yıldırım Üçtuğ -Solved Problems - CH3 Q-8 --- ## 6.9 kV(l-l) 50 Hz synchronous motor has a synchronous reactance of 95 Ohm/phase. For this problem all losses and saturation effect may be neglected. -- ### a) Compute the armature current and pf of the motor when supplying 700kW rated power and the load angle is 54.4 degrees. -- ### b) Compute the maximum power this motor can deliver if its field excitation is kept constant at the value in part a. Compute the power factor and armature current. --- ## 6.9 kV(l-l) 50 Hz synchronous motor has a synchronous reactance of 95 Ohm/phase. For this problem all losses and saturation effect may be neglected. ### c) What should be the minimum percentage increase in the field current for the motor to supply 1 MW power. -- ### d) What should be the excitation voltage for the motor to supply rated power while drawing minimum armature current? --- ## [Solutions](./files/ee362_recitation2.pdf) --- ## You can download this presentation from: [keysan.me/ee362](http://keysan.me/ee362) ---