Conventional DC Machines and Universal Motor - …

1 Electricity and New Energy Conventional DC Machines and Universal Motor Student Manual 88943-00 Order no.: 88943-00 First Edition Revision level: 01/2015 By the staff of Festo Didactic Festo Didactic Lt e/Ltd, Quebec, Canada 2013, 2014 Internet: e-mail: Printed in Canada All rights reserved ISBN 978-2-89640-579-4 (Printed version) ISBN 978-2-89640-580-0 (CD-ROM) Legal Deposit Biblioth que et Archives nationales du Qu bec, 2014 Legal Deposit Library and Archives Canada, 2014 The purchaser shall receive a single right of use which is non-exclusive, non-time-limited and limited geographically to use at the purchaser's site/location as follows. The purchaser shall be entitled to use the work to train his/her staff at the purchaser's site/location and shall also be entitled to use parts of the copyright material as the basis for the production of his/her own training documentation for the training of his/her staff at the purchaser's site/location with acknowledgement of source and to make copies for this purpose.

2 In the case of schools/technical colleges, training centers, and universities, the right of use shall also include use by school and college students and trainees at the purchaser's site/location for teaching purposes. The right of use shall in all cases exclude the right to publish the copyright material or to make this available for use on intranet, Internet and LMS platforms and databases such as Moodle, which allow access by a wide variety of users, including those outside of the purchaser's site/location. Entitlement to other rights relating to reproductions, copies, adaptations, translations, microfilming and transfer to and storage and processing in electronic systems, no matter whether in whole or in part, shall require the prior consent of Festo Didactic GmbH & Co.

3 KG. Information in this document is subject to change without notice and does not represent a commitment on the part of Festo Didactic. The Festo materials described in this document are furnished under a license agreement or a nondisclosure agreement. Festo Didactic recognizes product names as trademarks or registered trademarks of their respective holders. All other trademarks are the property of their respective owners. Other trademarks and trade names may be used in this document to refer to either the entity claiming the marks and names or their products. Festo Didactic disclaims any proprietary interest in trademarks and trade names other than its own. Festo Didactic 88943-00 III Safety and Common Symbols The following safety and common symbols may be used in this manual and on the equipment: Symbol Description DANGER indicates a hazard with a high level of risk which, if not avoided, will result in death or serious injury.

4 WARNING indicates a hazard with a medium level of risk which, if not avoided, could result in death or serious injury. CAUTION indicates a hazard with a low level of risk which, if not avoided, could result in minor or moderate injury. CAUTION used without the Caution, risk of danger sign , indicates a hazard with a potentially hazardous situation which, if not avoided, may result in property damage. Caution, risk of electric shock Caution, hot surface Caution, risk of danger Caution, lifting hazard Caution, hand entanglement hazard Notice, non-ionizing radiation Direct current Alternating current Both direct and alternating current Three-phase alternating current Earth (ground) terminal Safety and Common Symbols IV Festo Didactic 88943-00 Symbol Description Protective conductor terminal Frame or chassis terminal Equipotentiality On (supply) Off (supply) Equipment protected throughout by double insulation or reinforced insulation In position of a bi-stable push control Out position of a bi-stable push control Festo Didactic 88943-00 V Table of Contents Preface.

5 IX About This Manual .. XI Unit 1 Fundamentals of Rotating Machines .. 1 DISCUSSION OF FUNDAMENTALS .. 1 Basic Motor operation .. 1 The rotating electromagnet principle .. 3 The generator principle .. 7 Work, torque, and power .. 10 Work .. 10 Torque .. 11 Power .. 12 Electric Motor efficiency .. 12 Ex. 1-1 Prime Mover and Brake Operation .. 15 DISCUSSION .. 15 Introduction to the Four-Quadrant Dynamometer/Power Supply .. 15 Two-quadrant constant-torque brake .. 15 Clockwise constant-speed prime mover/brake .. 16 Counterclockwise constant-speed prime mover/brake .. 17 Speed, torque, and mechanical power measurements using the Four-Quadrant Dynamometer/Power Supply .. 18 Motor operation .. 18 Generator operation .. 18 PROCEDURE.

6 19 Set up and connections .. 19 Two-quadrant, constant-torque brake operation .. 22 Constant-speed prime mover operation .. 25 Constant-speed prime mover driving a loaded generator .. 29 Unit 2 DC Motors and Generators .. 37 DISCUSSION OF FUNDAMENTALS .. 37 Operating principle of dc motors .. 37 Operating principle of dc generators .. 41 Table of Contents VI Festo Didactic 88943-00 Ex. 2-1 The Separately-Excited DC Motor .. 45 DISCUSSION .. 45 Simplified equivalent circuit of a dc Motor .. 45 Relationship between the Motor rotation speed and the armature voltage when the armature current is constant .. 47 Relationship between the Motor torque and the armature current .. 48 Relationship between the Motor rotation speed and the armature voltage when the armature current varies.

7 48 PROCEDURE .. 50 Set up and connections .. 50 Determining the armature resistance .. 53 Motor speed versus armature voltage .. 54 Motor torque versus armature current .. 56 Speed decrease versus armature current .. 58 Additional experiments (optional) .. 60 Motor speed-versus-armature voltage and Motor torque-versus-armature current characteristics for reversed armature connections .. 60 Ex. 2-2 Separately-Excited, series , Shunt, and Compound Motors .. 63 DISCUSSION .. 63 Separately-excited dc Motor .. 63 series Motor .. 65 Shunt Motor .. 66 Compound Motor .. 67 PROCEDURE .. 69 Set up and connections .. 69 Speed-versus-armature voltage characteristic of a separately-excited dc Motor .. 73 Torque-versus-armature current characteristic of a separately-excited dc Motor .

8 74 Speed-versus-torque characteristic of a series Motor .. 76 Additional experiments (optional) .. 78 Motor speed-versus-torque characteristic of a shunt Motor .. 78 Motor speed-versus-torque characteristic of a cumulative compound Motor .. 79 Ex. 2-3 Separately-Excited, Shunt, and Compound DC Generators .. 83 DISCUSSION .. 83 Introduction to dc generators .. 83 Separately-excited dc generator .. 84 Self-excited dc generator .. 86 Voltage-versus-current characteristics of various dc generators .. 87 Table of Contents Festo Didactic 88943-00 VII PROCEDURE .. 88 Set up and connections .. 88 Output voltage-versus-speed characteristic of a separately-excited dc generator .. 91 Output current-versus-torque characteristic of a separately-excited dc Motor .

9 93 Output voltage versus field current characteristic of a separately-excited dc generator .. 96 Output voltage-versus-output current characteristic of a separately-excited dc generator operating at a fixed speed .. 98 Additional experiments (optional) .. 99 Output voltage-versus-output current characteristic of a shunt generator operating at a fixed speed .. 99 Voltage-versus-current characteristic of a cumulative-compound generator operating at a fixed speed .. 100 Output voltage-versus-output current characteristic of a differential compound generator operating at a fixed speed .. 101 Unit 3 Special Characteristics of DC Motors .. 105 DISCUSSION OF FUNDAMENTALS .. 105 Ex. 3-1 Armature Reaction and Saturation Effect .. 107 DISCUSSION.

10 107 Armature reaction .. 107 Saturation effect .. 110 PROCEDURE .. 111 Effect of the armature reaction on the output voltage of a dc generator .. 111 Set up and connections .. 113 Effect of the armature reaction on torque .. 116 Effect of the saturation on torque .. 117 Additional experiment (optional) .. 122 Effect of the armature reaction on the torque developed by a dc Motor .. 122 Ex. 3-2 The Universal Motor .. 123 DISCUSSION .. 123 Table of Contents VIII Festo Didactic 88943-00 PROCEDURE .. 125 Set up and connections .. 126 Direction of rotation of a dc series 129 DC series Motor operating on ac power .. 131 Direction of rotation of a Universal Motor operating on dc power .. 133 Universal Motor operating on ac 136 Effect of the compensating winding.