73122 - Electric Drives (2nd cycle)

Learning outcomes

The student acquires the knowledge of the main types of electric drives used in industrial automation. In particular, the dynamic models of electric machines, useful to implement torque and speed control schemes, will be developed. The student will be able to select, size, and simulate the electric drive more suitable for the specific application.

Course contents

DC motor drives

• Separately excited DC machines. Mathematical model.
• Steady state characteristics with armature and field control. Control of DC motors in the constant torque control region and in the field-weakening region.
• Transition from driving to breaking operation.
• Constant torque and constant horsepower operation.
• Dynamic model of the DC machine.
• Dynamic behavior of DC motors with constant flux.
• Block diagram of a DC motor coupled with a mechanical load. Torque production and control. Closed-loop control of torque and speed.
• Field weakening.
• Starting and speed reversal transients.
• Application DC motor drives.

 

Brushless DC motor drives

• Magnetic circuit analysis.
• Torque and back-emf equations.
• Winding inductances and armature reaction.
• Torque/speed characteristics: performance and efficiency.
• Three-phase brushless DC motor.
• Position sensors.
• Drive characteristics and control principles.
• Application of brushless DC motor drives.

Brushless AC motor drives

• Dynamic model of permanent magnet synchronous machines with surface mounted magnets.
• The dq machine and flux equations.
• Principles of field orientation.
• Torque production and control.
• Dynamic model of permanent magnet synchronous machines with interior magnets.
• The dq machine and flux equations.
• Torque production and control.
• Control of the synchronous machine supplied by current controlled PWM inverter.
• Simulation of electromechanical transients.
• Maximum torque capability of the machine in the flux weakening region.

Induction motor drives

• Dynamic model of induction machines.
• The dq machine and flux equations.
• Torque equation. Principles of field orientation.
• Machine equations and torque in the rotor flux oriented reference frame.
• Decoupling control of flux and torque in the rotor flux oriented reference frame.
• Flux models.
• Direct scheme and indirect scheme of induction motor field oriented control.
• Control of the induction machine supplied by current controlled PWM inverter.
• Simulation of electromechanical transients.
• Maximum torque capability of the machine in the flux weakening region. Applications.

Stepper motors and Switched-Reluctance Motors

• Reluctance torque.
• Fundamentals of stepper motors.
• Design of a stepper motor. Hybrid stepper motors.
• Torque characteristics. Stability region and behavior at high speed.
• Power converters for stepper motors.
• Structure of a switched reluctance motor.
• Design of a SRM.
• Torque expression and control loop.
• Lead angle.
• Behavior of SRMs at high speed.

Readings/Bibliography

• I. Boldea, S. A. Nasar : ELECTRIC DRIVES, CRC Press, New York.
• P. Vas: VECTOR CONTROL of AC MACHINES, Oxford University Press, New York.
• T.J.E. Miller: SWITCHED RELUCTANCE MOTORS AND THEIR CONTROL.Clarendon Press, Oxford.
• W. Leonard: CONTROL OF ELECTRICAL DRIVES. Springer-Verlag, Berlin.
• I. Boldea, S. A. Nasar : ELECTRIC DRIVES, CRC Press, New York.
• P. Vas: VECTOR CONTROL of AC MACHINES, Oxford University Press, New York.
• T.J.E. Miller: SWITCHED RELUCTANCE MOTORS AND THEIR CONTROL.Clarendon Press, Oxford, 1993.
• W. Leonard: CONTROL OF ELECTRICAL DRIVES. Springer-Verlag, Berlin, 2001

 

Teaching methods

The theoretical explanations are integrated by numerical simulations of electrical drives in SIMULINK/MATLAB

Assessment methods

The exam consists of an oral examination, which is based on three questions.

Teaching tools

Lessons are carried out with the help of a personal computer and a computer projector (Power Point). The pdf files of the slides utilized during the lessons are available. Exercises are carried out in the classroom with the help of a personal computer and a computer projector (MATLAB-Simulink).

Office hours

See the website of Michele Mengoni