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Electric Power / Controls Courseware Sample 85822-F0 A ELECTRIC POWER / CONTROLS COURSEWARE SAMPLE by the Staff of Lab-Volt Ltd. Copyright © 2009 Lab-Volt Ltd. All rights reserved. No part of this publication may be reproduced, in any form or by any means, without the prior written permission of Lab-Volt Ltd. Printed in Canada October 2009 Table of Contents Introduction ................................................... V Courseware Outline Asynchronous and Doubly-Fed Generators ........................ VII Sample Exercise Extracted from Asynchronous and Doubly-Fed Generators Exercise 3-9 The Boost Chopper ...............................3 Instructor Guide Sample Exercise Extracted from Asynchronous and Doubly-Fed Generators Exercise 3-11 The Four-Quadrant Chopper .......................17 Bibliography III IV Introduction The Lab-Volt Asynchronous and Doubly-Fed Generators system, model 8052-1, introduces the principles of electrical power generation and control in the field of wind turbines. Known as the standard for technical training systems in use across virtually every industry and around the globe, Lab-Volt is now using its expertise to facilitate the development, production, installation, and maintenance of the widest variety of Alternative and Renewable Energy Power Training Systems. While most power generation requires the creation, management, and conversion of heat energy into motion—with most variations simply involving the way heat is produced—alternative and renewable sources are far more varied. Many take advantage of the motion already found in nature; others harness nature’s own renewable forms of heat and energy. Capturing and converting that motion or energy often requires very non-traditional methods. Accustomed to breaking down processes and procedures into elemental blocks, Lab-Volt’s new training systems take the esoteric and theoretical out of the laboratory and translate it into apparatus that introduce practical, understandable teaching methods. Regardless of the operational scale of the alternative energy sources , Lab-Volt has distilled the essential elements of the process down to safe, hands-on classroom applications, developing each training product and process to yield realistic, repeatable, and logical results. V VI Courseware Outline ASYNCHRONOUS AND DOUBLY-FED GENERATORS Unit 1 Fundamentals for Rotating Machines Introduction to rotating machines. Work, speed, torque, and power. Operation of the Prime Mover / Dynamometer module. Ex. 1-1 Prime Mover Operation Familiarization with the Prime Mover / Dynamometer module operating in the Prime Mover mode. Prime mover speed versus voltage. Friction torque versus speed. Measurement of the opposi- tion torque caused by the machine driven by the Prime Mover. Unit 2 AC Induction Motors The principles of electromagnetic induction. Rotating magnetic field and synchronous speed. Demonstrating the operation and characteristics of AC induction motors. Ex. 2-1 The Three-Phase Squirrel-Cage Induction Motor Creating a rotating magnetic field in a three-phase squirrel-cage induction motor. Synchronous speed. Description and operation of the Three-Phase Squirrel-Cage Induction Motor. Torque versus speed characteristic. Reactive power required for creating the rotating magnetic field. Ex. 2-2 Eddy-Current Brake and Asynchronous Generator Description and operation of the eddy-current brake. Operating a three-phase squirrel-cage induction motor as an asynchronous generator. Demonstrating that an asynchronous generator can supply active power to the AC power network. Demonstrating that asynchronous generator operation requires reactive power. Ex. 2-3 Effect of Voltage on the Characteristics of Induction Motors Saturation in induction motors. Nominal voltage of a squirrel-cage induction motor. Demonstrating the effect of the motor voltage on the torque versus speed characteristic of a squirrel-cage induction motor. Unit 3 Power Electronics Fundamentals Introduction to Reversible DC Power Supply, Rectifiers, Choppers, Inverters, High-Speed Power Switching, and Effect of Frequency in Magnetic Circuits. VII Courseware Outline ASYNCHRONOUS AND DOUBLY-FED GENERATORS Ex. 3-1 Familiarization with the Reversible DC Power Supply The reversible DC power supply. Implementing a reversible DC power supply using a separately-excited DC motor/generator and a synchronous or asynchronous motor/generator. Operation of a reversible DC power supply implemented with a separately- excited DC motor/generator and a three-phase squirrel-cage induction motor/generator (asynchronous motor/generator). Ex. 3-2 Power Diode Single-Phase and Two-Phase Rectifiers Operating principles of the diode. Half-wave rectifier. Rectifier with free-wheeling diode. Battery charger circuit. Single-phase bridge rectifier. Two-phase half-wave rectifier. Ex. 3-3 Power Diode Three-Phase Rectifiers Three-phase, three-pulse rectifier. Three-phase, six-pulse rectifier. Ex. 3-4 Familiarization with the Chopper / Inverter Control Unit (Chopper Modes) Description of the controls, connectors, and indicators of the Chopper / Inverter Control Unit. Operation and use of the Chopper / Inverter Control Unit in a PWM-control chopper and a two-step neutral-zone (bang-bang) control chopper. Examples of various types of choppers built with IGBTs. Ex. 3-5 Familiarization with the Chopper / Inverter Control Unit (Inverter Modes) Operation and use of the Chopper / Inverter Control Unit in various two-phase and three-phase inverters. Introduction to the 120E-, 180E-, and programmed-waveform modulations. Use of synchron- ous pulse-width modulation (PWM) to obtain a constant V/f ratio three-phase inverter. Examples of inverters built with electronic switches. Ex. 3-6 Familiarization with the IGBT Chopper / Inverter Module Description of the IGBT Chopper / Inverter. Operation of the IGBT Chopper / Inverter module used as a buck chopper. Effect of the duty cycle on the power delivered. Ex. 3-7 Introduction to High-Speed Power Switching Voltage-type circuit. Current-type circuit. Free-wheeling diodes. Use of a capacitor to obtain a voltage-type source. Interconnecting voltage- and current-type circuits. VIII Courseware Outline ASYNCHRONOUS AND DOUBLY-FED GENERATORS Ex. 3-8 The Buck Chopper Operation of a buck chopper in a simple circuit with a resistive/inductive load. Power flow. Voltage transfer ratio versus the duty cycle. Effect of frequency on the output voltage and current. Power efficiency. Ex. 3-9 The Boost Chopper Operation of a boost chopper in a simple circuit with a resistive load. Power flow. Voltage transfer ratio versus the duty cycle. Effect of frequency on the output voltage and current. Power efficiency. Ex. 3-10 The Buck / Boost Chopper Operation of a buck/boost chopper in a simple circuit with two DC power supplies. Power flow. Voltage transfer ratio versus duty cycle. Ex. 3-11 The Four-Quadrant Chopper Operation of a four-quadrant chopper in a simple circuit with a resistive load. Voltage transfer ratio versus the duty cycle. Power flow. Observing four-quadrant operation on an oscilloscope. Ex. 3-12 The Single-Phase Inverter Using a four-quadrant chopper as a single-phase inverter with variable voltage and frequency (variable voltage and frequency single-phase ac network). A simple dual-polarity DC power supply. Operation of a single-phase inverter built with a dual-polarity DC power supply and two electronic switches, and using either pulse-width modulation (PWM) or 180E-modulation. Ex. 3-13 Saturation and Effect of Frequency in Magnetic Circuits The phenomenon of saturation in magnetic circuits. Saturation curve of magnetic circuits. Effect of frequency in magnetic circuits. Unit 4 Wound-Rotor Induction Machines Familiarization with the operation and characteristics of wound-rotor induction motor and doubly-fed induction generator. IX Courseware Outline ASYNCHRONOUS AND DOUBLY-FED GENERATORS Ex. 4-1 Wound-Rotor Induction Motor To examine the construction of the Three-Phase Wound-Rotor Induction Motor. To understand exciting current, synchronous speed and slip in a wound-rotor induction motor. To observe the effect of the revolving field and rotor speed upon the voltage induced in the rotor. Ex. 4-2 Wound-Rotor Induction Motor with Short-Circuited Rotor To observe the starting characteristics of the Three-Phase Wound-Rotor Induction Motor having short-circuited rotor windings. You will also show the rotor and stator currents at different motor speeds. Ex. 4-3 Wound-Rotor Induction Motor with Variable Rotor Resistors To observe speed control using external variable resistors connected in series with the rotor windings. Ex. 4-4 Wound-Rotor Frequency Conversion Principles To observe no-load and full-load characteristics of a rotary frequency converter. Ex. 4-5 Speed Control of a Wound-Rotor Generator Using Rotor Resistors To demonstrate how the speed of a wound-rotor generator can be controlled by varying the resistance of the rotor windings. Ex. 4-6 Variable Speed Doubly-Fed Induction Generator Using Rotor Frequency Injection To demonstrate how to synchronize a generator to an AC power network, demonstrate how a doubly-fed induction generator can produce output power at various speeds, how to control the output power level, and how to control the power factor of a generator. Appendices A Circuit Diagram Symbols B Impedance Tables C Equipment Utilization Chart D Reversible DC Power Supply E New Terms and Words F Configuration Files G Saving a Window in WordPad X Sample Exercise Extracted from Asynchronous and Doubly-Fed