Objective:
- Design and Development of converter, inverter model using MATLAB simulation.
- Design and development of Induction motor drive MATLAB model for speed control.
- Measurement of different parameters experimentally such as speed torque current of Induction motor drive.
Apparatus Required:
| Sl. No | Name | Specification | Remarks |
| 01 | Single phase Induction motor controller using cyclo-converter Kit | 01 nos. | |
| 02 | Single phase Induction motor with spring load | 0.5HP, 230 V, 5A 1400 rpm | 01 nos. |
| 03 | CRO | 01 nos. | |
| 04 | Tachometer | Digital Type | 01 nos. |
Circuit Diagram:
Theory:
Cycloconverters are basically frequency conversion devices and transform higher frequencies to lower frequencies. The alternating voltage at supply frequency is converted directly to lower frequency without any DC intermediate stage. The advent of thyristors and sophisticated transistorized control circuitry have made them very popular for industrial applications. In the given setup, two SCR based full bridges are connected to the load with P bridge and N bridge. Microcontroller based firing circuit provides pulses for the group of SCRs. One bridge fire at time, with P bridge fires at +ve half cycle of the supply. Similarly N bridge SCRs are fired at –ve half cycle. The optoisolator provides the required isolation for control circuit and power circuit. Pot P1 provides the firing control.
Procedures:
- In the given setup Dedicated 8 Pin Johnson socket is provided on the main panel for connecting motors. Motor is provided with an 8 pin Johnson plug and with heavy duty 3 core cable. Connect the motor to the panel before switching on the unit.
- Now if you want to connect CRO to observe output waveform, we recommend connecting the mains plug of CRO into the isolation transformer 3 pin socket provided on the front panel. Then connect the probes of CRO into attenuated output terminals for CRO.
- Keep Frequency control pot P2 at 50 Hz.
- For 50Hz selected, Pot P1 (firing angle control) will control output voltage from zero to 230V. For 25Hz,16.6 Hz ,12.5 Hz firing angle is controlled such that maximum output voltage is 110V roughly. This is particularly done using software to limit the maximum output current at 5 Amp.
- Now you may switch on the Power on switch.
- Remove the complete loading on the motor.
- Now slowly increase the motor voltage.
- You may observe that as we change the frequency from 50Hz to 25 Hz, there is a sudden increase in output current. At this point, always adjust output voltage a bit so that maximum current does not go beyond 5 amp.
- You may load the motor at different frequencies and measure the torque and speed.
Observation Table: With No-Load
| Sl. No | Output Frequency (f) in Hz. | Output Voltage (V) in Volts. | Load current (I) in amps. | Speed (N) in RPM | W1 in Kg. | W2 in Kg. | W=(W1-W2) in Kg. | Torque (T) in N-m |
| 1 | ||||||||
| 2 | ||||||||
| 3 | ||||||||
| 4 | ||||||||
| 5 | ||||||||
| 6 |
Conclusion: Written by students.