37064 - Electrical Drives T

Learning outcomes

At the end of the course, the student knows: - the most common electric drives and the problems related to their use in industrial automation applications - the operating characteristics and the performance of electric drives that use DC machines, brushless DC and AC motors, induction machines, stepper motors and direct type actuators, powered by electronic power converters - the steady-state and dynamic models of electric machines. In addition, the student is able to understand the operation of torque and speed control schemes for electric drives, as well as the principles for sizing and selecting the most suitable electric motor in specific applications.

Course contents

• Introduction
  General information on electrical machines and drives. Review of electrical engineering. Magnetic materials and conductive materials. Magnetic circuits. Electromechanical energy conversion principles. Heat dissipation in electrical machines.
  
  
• Principles of static electric energy conversion
  Introduction to power electronic components. Controlled and uncontrolled rectifiers, choppers, three-phase inverters, square-wave and PWM control techniques.
  
  
• DC motor drives
  DC motors: structure, operating principle, mathematical model, mechanical characteristic. Speed regulation with armature and excitation control. Constant torque and constant power operation. Axes and spindle drives. Features of drives with controlled rectifiers. Features of drives with choppers. Drive structures for operation on two and four quadrants. Block diagram of the DC motor. Analysis of electromechanical transients with voltage supply. Torque control. Speed control. Analysis and tuning of torque and speed regulators. Simulation of complete motor drives in MATLAB-Simulink environment.
  
  
• Brushless DC motor drives
  Brushless DC motors: structure and operating principle. Phase supply sequence according to the rotor position. Six-step operation. Switching transients and torque oscillations. Motor drive block scheme. Applications.
  
  
• Brushless AC motor drives
  Synchronous motors with round rotor and salient pole rotor: structure and operating principle. Synchronous motors with permanent magnets. Machine equations, vectorial diagrams and torque expression in steady-state conditions. Operating characteristics with voltage and frequency supply. Inverter power supply for speed control. Multi-motor drives. Closed-loop operation with current control. Brushless AC motors. Power supply technology with PWM current regulators. Block diagram of the motor drive. Dynamic model of synchronous machines based on the theory of d-q axes. Field-oriented control. Analysis of limit performance in torque and speed. Simulation of complete motor drives in the MATLAB-Simulink environment.
  
  
• Induction motor drives
  Induction motors: structure, operating principle, equivalent circuit, mechanical characteristic. Inverter power supply for speed control. Open-loop control schemes. Volt per Hertz control. Acceleration ramps. Closed-loop control schemes. Slip frequency control. Constant torque and constant power operation. Dynamic model of induction machines based on d-q axes theory. Field-oriented control of induction motors. Direct and indirect torque control techniques. Rotor flux estimation. Torque and speed limits of induction motor drives. Simulation of complete motor drives in the MATLAB-Simulink environment.
  
  
• Stepper motor drives
  Stepper motors: structure and principle of operations. Simplified dynamic model. Power supply circuits and control techniques. Analysis of low and high speed instability problems. Analysis of torque limits as function of the supply frequency. Simulation of complete motor drives in the MATLAB-Simulink environment.

Readings/Bibliography

It is not necessary to buy specific books. The pdf files of the slides utilized during the lessons are indispensable and sufficient for the preparation for the exam. They are available on IOL. For further considerations:

I. Boldea, S. A. Nasar : ELECTRIC DRIVES, CRC Press, New York, 1999.

P. Vas: VECTOR CONTROL of AC MACHINES, Oxford University Press, New York, 1990.

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 frontal lessons are supported by exercises with Personal Computer (MATLAB-Simulink).

Assessment methods

The learning assessment is based on a final written test.

Teaching tools

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

Office hours

See the website of Michele Mengoni

See the website of Luca Zarri