# 28553 - Electric Drives

## Learning outcomes

At the end of the course, the student gains insights into the performance of the main electric drives through the analysis of the most common electric machines, power converters and industrial applications. In particular, the student can •model DC machines, synchronous machines and induction machines, •simulate the corresponding electric drives in Matlab/Simulink environment, •understand the closed-loop control schemes for the regulation of torque, speed and position of electric actuators and machines used in industrial applications.

## Course contents

Introduction and basic principles

Force on current-carrying conductor. Voltage induced in a moving conductor. Magnetic material and circuits. Coupled coils. Coefficient of coupling. Self and mutual inductances. Voltage equations. Stored energy in the magnetic field. Electromechanical energy conversion principles. Torque production principles. Types of electrical machines.

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. DC drives with force-commutated converters. Single-, double-, and four-quadrant 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. Starting and speed reversal transients. Application DC motor drives.

Brushless DC motor drives

Magnetic circuit analysis. Torque and emf equations. Winding inductances and armature reaction. Torque/speed characteristics: performance and efficiency. The three-phase half-wave brushless DC motor. The three-phase full-wave brushless DC motor. Commutation phenomena. Position sensors. Drive characteristics and control principles. Application of brushless DC motor drives.

Variable frequency synchronous motor drives

Magnetic circuit analysis of synchronous machines. Synchronous reactances (d-, q-axis). Torque and machine equations. Steady-state characteristics. Open-loop control of voltage source inverter drives. Starting performance by squirrel gage rotors. Closed-loop control of current controlled PWM inverter drives. Applications.

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

Analysis of induction motors based on steady-state machine model. Torque and machine equations. Steady-state characteristics. Starting of induction motors. Constant terminal volts/hertz operation. Torque characteristics. Low-frequency performance with increased volts/hertz. Constant air-gap flux operation. Torque characteristics. Current-source inverter drive with slip frequency control. Current controlled PWM inverter drive with slip frequency control. Constant-horsepower operation.

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

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

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 theoretical part of the course is integrated by numerical simulations of electrical drives in SIMULINK of MATLAB. Assignments of project works to groups of 3-5 students.

## Assessment methods

Discussion of theoretical topics and presentation of the project work

## Teaching tools

Copy of the transparencies employed for lecturing.

Basic mathematical models of electrical drives for numerical simulations

## Office hours

See the website of Domenico Casadei