ELECTROMECHANICAL SYSTEMS FIRST LABORATORY EXERCISE Instructions Remark: All files made during the working day are automatically deleted at the end of the day, or after 2 hours of computer idling. Therefore, it is necessary to bring a USB stick for saving data. General instructions for simulation start and settings • Open the C:\NASTAVA\ELESUS\RIAZ\contents.mdl file. • Use the button to start each simulation in its own simulation window, or choose the Simulation/Start command. Parameters Solver Options/Type: Variable-step; ode15s should be chosen in each newly opened simulation window within the Simulation/Simulation parameters menu. This procedure should be repeated within each new simulation window. Do not shut down the main window Table of contents during the entire exercise. Image saving instructions: Use the Array option to save images. You can find it within the Scope block, under the parameters block, within the Data history tab. You can enable this feature by checking the Save data to workspace mark. Additionaly, you should uncheck the Limit data points to last mark in that same tab. You should write the name of the desired waveform within the Variable name box. This will save the waveform to Workspace under the selected name as a two-column matrix (time-value pairs). Each matrix can be saved in .mat form and can be reopened in Matlab later on. It is recommended to use variable names which depict the waveforms of interest. For instance, while observing the speed of the DC machine during loading/deloading of the axes, a recommended name for the waveform would be n_DC_load_deload. Plot command is used to plot the waveforms, with columns of saved matrices as arguments of the function. Remark: You are requested to comment on the waveforms, especially to comment on any differences between the waveforms, when the parameters change. These comments have to contain the physical „hows“ and „whys“, for instance how and why does the loading/unloading of the machine influence the motor acceleration time, speed overshoot and armature current amount. ELECTROMECHANICAL SYSTEMS FIRST LABORATORY EXERCISE Instructions DC MACHINE OPERATION SIMULATION a) Open the DC MOTOR DRIVES menu by double-clicking on the DC MOTOR DRIVES icon. Select the DC motor ramp start button. Remove the integrator block and connect the ramping rate V/s block to the Va (armature voltage) motor block input. Leave the existing scope connected to that input. We'll use it to measure the armature voltage. Set the motor shaft torque (Tl – load torque) to 0Nm. Save the armature current and motor speed waveforms during motor start. Do this for the nominal armature voltage and for one-half of the nominal armature voltage.1 (the Info block contains data on nominal values of machine parameters). Save and compare the waveforms and comment on their differences. b) Set the armature voltage to nominal value. Set constant load torque values (Tl – load torque): 4 Nm, 15 Nm and 30 Nm.2 Save and compare the waveforms and comment on the differences. Remark: use the Simulink Library Browser Sources/Constant block instead of the step change in load torque Tl. c) Close the existing simulation window and reopen the DC MOTOR DRIVES icon. Select the DC motor transient running operation menu. Set the load torque step changes for times 0,5 s and 2 s from 1 Mn to 1,2 Mn and from 1,2 Mn to 0,8 Mn, respectively. This part of the simulation uses the per unit values ([pu]). Save the armature current and motor speed waveforms and comment on the motor behavior. AC MACHINE OPERATION SIMULATION d) Open the Steady–state characteristics of induction machines menu in the INDUCTION MACHINES icon, and start the simulation. You can access the waveforms by double clicking on the PLOTS icon. Plot the dependance of motor torque and current on motor slip. Set the armature voltage value to: 0,8 Un, 0,5 Un and 0,3 Un, plot the dependance of motor torque and current on motor slip and notice and comment on the differences. All parameter changes are made by double clickin on the motor icon. This part of the simulation uses the per unit values ([pu]). Set the armature voltage value back to the nominal value, adjust the synchronous speed to 0,8 ωs (simulation parameter ws), plot the torque and current dependance on slip and comment the differences regarding the ωs case. Adjust values of all parameters back to nominal and change the value of rotor resistance to 0,08 Rn, 0,15 Rn, 0,25 Rn and 0,30 Rn. Plot the charactristics and comment on the differences. This simulation saves the waveforms onto the Workspace under appropriate names automatically. e) Close the existing window and open the STEADY-STATE CHARACTERISTICS icon. Select the Volts per Hertz speed control of induction machines [SI] menu. Choose the Edit menu from the characteristics window to change the parameter values. Change the base frequency values (f0 value in the m-file editor) to 10 Hz, 25 Hz, 50 Hz and 75 Hz. Each change must be saved in Workspace before starting a new simulation. You can use the altgr+print screen method of saving images for this part of the exercise only. 1 2 Waveforms for both armature voltages must be plotted on the same image. Motor accelerations for different load torque values must be plotted on the same image.
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