Electric Machines and Drives
This lab provides hands-on experience in the modeling, control, and real-time implementation of electric motor drive systems. Students will characterize DC and AC machines, design closed-loop PI and V/f controllers, and analyze power electronics (DC-DC converters) critical for drive operation.
Objectives
- Demonstrate the ability to simulate and execute a pre-built DC motor speed control model in real-time on an inverter-motor drive platform.
- Investigate the theoretical background and verify the real-time operation of a switched-mode DC-DC converter.
- Master the techniques for determining the electrical and mechanical parameters and mathematical models for DC, PMAC, and Induction motors.
- Develop and implement a PI-controller based closed-loop system to achieve and maintain constant DC motor speed under varying load conditions.
- Simulate and practically emulate the four-quadrant operation (motoring and braking) of a DC motor.
- Experimentally determine the torque-load angle characteristic of a PMAC motor and the torque-speed characteristic of an Induction motor.
- Implement and evaluate the performance of AC speed control methods such as V/f control and hysteretic current control.
- Evaluate the differences in modeling, control requirements, and complexity among DC, PMAC, and Induction motor drive systems.
Photos
Equipment
Three‑inverter and motor drive (CUSP Electric Drives Kit)
Sciamble Corp.
Isolated DC power supply
B&K Precision Corporation
Digital multimeter
B&K Precision Corporation
Digital storage oscilloscope (optional)
Tektronix
Experiments
Description: In this experiment, a pre-built DC motor speed control model will be simulated as well as run in real-time, as an introduction to the electric drives laboratory kit.
Description: In the previous experiment, a pre-built DC motor speed control model was simulated and executed in real-time. In this experiment, one of the components, the switched mode converter will be explored in further detail. The next section deals with the theoretical background for this experiment followed by the simulation of a switched-mode DC converter. Finally, the simulation model is verified in real-time.
Description: A DC motor can be mathematically modeled as an electrical system and a mechanical system, tied together by relationship between back-emf and speed, and relationship between current and torque. In this experiment, the electrical and mechanical parameters of the DC motor are determined. These values are necessary to design a proper control system to control motor speed, torque, or position as will be seen in later experiments.
Description: In this experiment, a mathematical model of a permanent magnet DC motor will be simulated based on the parameters estimated in the previous experiment. It will be shown that the motor speed cannot be held a constant under varying load and voltage conditions. To overcome this, a closed loop system will be developed using a PI controller so that the output speed closely matches the desired speed under various load conditions. Finally, the designed system will be run in real-time to control the actual DC motor at constant speed.
Description: In this experiment, four quadrant operation of a DC motor is simulated as well as run in real-time. The speed and current control model developed in the previous experiment is used to emulate the four regions of operation.
Description: In this experiment, permanent magnet AC motor's load-angle variation as function of electromagnetic torque is characterized. This is followed by closed loop speed control using hysteretic current control.
Description: Similar to a DC motor, a 3Φ AC Induction motor can be mathematically modeled as an electrical and a mechanical system related by back-emf to speed and current-torque relationships. In this experiment, the electrical and mechanical parameters of the Induction motor are determined. These values are necessary to design proper control system to control motor speed, torque, or position.
Description: In this experiment, the open loop torque-speed characteristic of an induction motor will be measured. As will be seen, the motor speed does not remain a constant and tends to drop linearly with increasing load torque. The torque-speed characteristic will then be measured under closed loop V/f based speed control.
Resources
Safety considerations when working in power electronics
Open resource →Textbook
Electric Machines and Drives: A First Course
Ned Mohan · Wiley