Single-Phase Asynchronous Machine
Open the Measurements library and copy a Voltage Measurement block into your model. Change the block name to VAB. To control your inverter bridge, you need a pulse generator.
The converter operates in an open loop, and the three PWM modulating signals are generated internally. Connect the P output to the pulses input of the Universal Bridge block. The block has been discretized so that the pulses change at multiples of the specified time step. One common method of generating the PWM pulses uses comparison of the output voltage to synthesize 60 Hz in this case with a triangular wave at the switching frequency Hz in this case.
The line-to-line RMS output voltage is a function of the DC input voltage and of the modulation index m as given by the following equation:. Therefore, a DC voltage of V and a modulation factor of 0. You now add blocks measuring the fundamental component 60 Hz embedded in the chopped Vab voltage and in the phase A current.
Duplicate the Fourier block. Stream these signals to the Simulation Data Inspector: Set the stop time to 1 s and start the simulation. Open the Simulation Data Inspector and look at the signals. As expected, the magnitude of the 60 Hz voltage contained in the chopped wave stays at. Also notice strong oscillations of the electromagnetic torque at starting. If you zoom in on the torque in steady state, you should observe a noisy signal with a mean value of If you zoom in on the three motor currents, you can see that all the harmonics multiples of the Hz switching frequency are filtered by the stator inductance, so that the 60 Hz component is dominant.
The Universal Bridge block is not a conventional subsystem where all the six individual switches are accessible. If you want to measure the switch voltages and currents, you must use the Multimeter block, which gives access to the bridge internal signals:.
Open the Universal Bridge dialog box and set the Measurement parameter to Device currents. Copy the Multimeter block from the Measurements library into your circuit. Double-click the Multimeter block. A window showing the six switch currents appears. Select the two currents of the bridge arm connected to phase A.
They are identified as. The number of signals 2 is displayed in the Multimeter icon. The waveforms obtained for the first 20 ms are shown in this plot. As expected, the currents in switches 1 and 2 are complementary. A positive current indicates a current flowing in the IGBT, whereas a negative current indicates a current in the antiparallel diode. Multimeter block use is not limited to the Universal Bridge block.
Many blocks of the Electrical Sources and Elements libraries have a Measurement parameter where you can select voltages, currents, or saturable transformer fluxes. A judicious use of the Multimeter block reduces the number of current and voltage sensors in your circuit, making it easier to follow. You might have noticed that the simulation using a variable-step integration algorithm is relatively long.
Depending on your computer, it might take tens of seconds to simulate one second. To shorten the simulation time, you can discretize your circuit and simulate at fixed simulation time steps. Open the powergui block and set Simulation type to Discrete. Set the Sample time to 10e-6 s. Observe that the simulation is now faster than with the continuous system.
Results compare well with the continuous system. The two Fourier blocks allow computation of the fundamental component of voltage and current while simulation is running. If you would like to observe harmonic components also you would need a Fourier block for each harmonic.
This approach is not convenient. Now use the FFT tool of powergui to display the frequency spectrum of voltage and current waveforms. When the simulation is complete, open the powergui and select FFT Analysis. Translated by Mouseover text to see original. Click the button below to return to the English version of the page. This page has been translated by MathWorks. Click here to see To view all translated materials including this page, select Country from the country navigator on the bottom of this page.
The automated translation of this page is provided by a general purpose third party translator tool. MathWorks does not warrant, and disclaims all liability for, the accuracy, suitability, or fitness for purpose of the translation. This example shows the operation of a single phase asynchronous motor in Capacitor-Start and Capacitor-Start-Run operation modes.
This model uses two single-phase asynchronous motors respectively in Capacitor-Start and Capacitor-Start-Run modes, in order to compare their performance characteristics, such as torque, torque pulsation, efficiency and power factor.
They have identical stator windings main and auxiliary and rotor squirrel cages. Motor 1 motor operates in capacitor-start mode. The starting capacitor is used to provide a high starting torque. Motor 2 operates in capacitor-start-run mode. This operation mode uses two capacitors: The run and start capacitors. During the starting period, the auxiliary winding is also connected in series with a uF capacitor but, after the disconnection speed has been reached, the auxiliary winding stays connected in series with a This capacitor value is optimized to mitigate torque pulsations.
The motor operates efficiently with a high power factor.