Control of Electrical Drives

Electrical drives play an important role as electromechanical energy convert­ ers in transportation, material handling and most production processes. The ease of controlling electrical drives is an important aspect for meeting the in­ creasing demands by the user with respect to flexibility and precision, caused by technological progress in industry as well as the need for energy conser­ vation. At the same time, the control of electrical drives has provided strong incentives to control engineering in general, leading to the development of new control structures and their introduction to other areas of control. This is due to the stringent operating conditions and widely varying specifications - a drive may alternately require control of torque, acceleration, speed or position - and the fact that most electric drives have - in contrast to chem­ ical or thermal processes - well defined structures and consistent dynamic characteristics. During the last years the field of controlled electrical drives has undergone rapid expansion due mainly to the advances of semiconductors in the form of power electronics as well as analogue and digital signal electronics, eventu­ ally culminating in microelectronics and microprocessors. The introduction of electronically switched solid-state power converters has renewed the search for adjustable speed AC motor drives, not subject to the limitations of the mechanical commutator of DC drives which dominated the field for a century.

Inhalt

1. Elementary Principles of Mechanics.- 1.1 Newtons Law.- 1.2 Moment of Inertia.- 1.3 Effect of Gearing.- 1.4 Power and Energy.- 1.5 Experimental Determination of Inertia.- 2. Dynamics of a Mechanical Drive.- 2.1 Equations Describing the Motion of a Drive with Lumped Inertia.- 2.2 Two Axes Drive in Polar Coordinates.- 2.3 Steady State Characteristics of Motors and Loads.- 2.4 Stable and Unstable Operating Points.- 3. Integration of the Simplified Equation of Motion.- 3.1 Solution of the Linearised Equation.- 3.1.1 Start of a Motor with Shunt-type Characteristic at No-load.- 3.1.2 Starting the Motor with a Load Torque Proportional to Speed.- 3.1.3 Loading Transient of the Motor Initially Running at No-load Speed.- 3.1.4 Starting of a DC Motor by Sequentially Short-circuiting Starting Resistors.- 3.2 Analytical Solution of Nonlinear Differential Equation.- 3.3 Numerical and Graphical Integration.- 4. Thermal Effects in Electrical Machines.- 4.1 Power Losses and Temperature Restrictions.- 4.2 Heating of a Homogeneous Body.- 4.3 Different Modes of Operation.- 4.3.1 Continuous Duty.- 4.3.2 Short Time Intermittent Duty.- 4.3.3 Periodic intermittent duty.- 5. Separately Excited DC Machine.- 5.1 Introduction.- 5.2 Mathematical Model of the DC Machine.- 5.3 Steady State Characteristics with Armature and Field Control.- 5.3.1 Armature Control.- 5.3.2 Field Control.- 5.3.3 Combined Armature and Field Control.- 5.4 Dynamic Behaviour of DC Motor with Constant Flux.- 6. DC Motor with Series Field Winding.- 6.1 Block Diagram of a Series-wound Motor.- 6.2 Steady State Characteristics.- 7. Control of a Separately Excited DC Machine.- 7.1 Introduction.- 7.2 Cascade Control of DC Motor in the Armature Control Region.- 7.3 Cascade Control of DC Motor in the Field-weakening Region.- 7.4 Supplying a DC Motor from a Rotating Generator.- 8. Static Converter as a Power Actuator for DC Drives.- 8.1 Electronic Switching Devices.- 8.2 Line-commutated Converter in Single-phase Bridge Connection.- 8.3 Line-commutated Converter in Three-phase Bridge Connection.- 8.4 Line-commutated Converters with Reduced Reactive Power.- 8.5 Control Loop Containing an Electronic Power Converter.- 9. Control of Converter-supplied DC Drives.- 9.1 DC Drive with Line-commutated Converter.- 9.2 DC Drives with Force-commutated Converters.- 10. Symmetrical Three-Phase AC Machines.- 10.1 Mathematical Model of a General AC Machine.- 10.2 Induction Motor with Sinusoidal Symmetrical Voltages in Steady State.- 10.2.1 Stator Current, Current Locus.- 10.2.2 Steady State Torque, Efficiency.- 10.2.3 Comparison with Practical Motor Designs.- 10.2.4 Starting of the Induction Motor.- 10.3 Induction Motor with Impressed Voltages of Arbitrary Wave- forms.- 10.4 Induction Motor with Unsymmetrical Line Voltages in Steady State.- 10.4.1 Symmetrical Components.- 10.4.2 Single-phase Induction Motor.- 10.4.3 Single-phase Electric Brake for AC Crane-Drives.- 10.4.4 Unsymmetrical Starting Circuit for Induction Motor.- 11. Power Supplies for Adjustable Speed AC Drives.- 11.1 Pulse width modulated (PWM) Voltage Source Transistor Converter (IGBT).- 11.2 Voltage Source PWM Thyristor Converter.- 11.3 Current Source Thyristor Converters.- 11.4 Converter Without DC Link (Cycloconverter).- 12. Control of Induction Motor Drives.- 12.1 Control of Induction Motor Based on Steady State Machine Model.- 12.2 Rotor Flux Orientated Control of Current-fed Induction Motor.- 12.2.1 Principle of Field Orientation.- 12.2.2 Acquisition of Flux Signals.- 12.2.3 Effects of Residual Lag of the Current Control Loops.- 12.2.4 Digital Signal Processing.- 12.2.5 Experimental Results.- 12.2.6 Effects of a Detuned Flux Model.- 12.3 Control of Voltage-fed Induction Motor.- 12.4 Field Orientated Control of Induction Motor with a Current Source Converter.- 12.5 Control of an Induction Motor Without a Mechanical Sensor.- 12.5.1 Machine Model in Stator Flux Coordinates.- 12.5.2 Example of an "Encoderless Control".- 12.5.3 Simulation and Experimental Results.- 12.6 Control of an Induction Motor Using a Combined Flux Model.- 13. Induction Motor Drive with Reduced Speed Range.- 13.1 Doubly-fed Induction Machine with Constant Stator Frequency and Field-orientated Rotor Current.- 13.2 Control of a Line-side Voltage Source Converter as a Reactive Power Compensator.- 13.3 Wound-Rotor Induction with Slip-Power Recovery.- 14. Variable Frequency Synchronous Motor Drives.- 14.1 Control of Synchronous Motors with PM Excitation.- 14.2 Synchronous Motor with Field- and Damper-Windings.- 14.3 Synchronous Motor with Load-commutated Inverter (LCI- Drive).- 15. Some Applications of Controlled Electrical Drives.- 15.1 Speed Controlled Drives.- 15.2 Lineax Position Control.- 15.3 Lineax Position Control with Moving Reference Point.- 15.4 Time-optimal Position Control with Fixed Reference Point.- 15.5 Time-optimal Position Control with Moving Reference Point.