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Practical Electric Motor Handbook

Electronics, Instrumentation Design and Engineering
Electric Motors, Generators and Drives Review

Practical Electric Motor Handbook
Irving Gottlieb
173 Pages

Open: Practical Electric Motor Handbook
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Practitioners in the various applied sciences tend to view electric motors as generic devices for converting electrical to mechanical energy. Certainly such a concept is entirely valid but in practice, however, it turns out to be just the tip of the iceberg; the very first prerequisite in grasping the basic framework of electric motor technology is an appreciation of the extensive classification needed to deal with these motors in the practical world.

To begin with, there are direct current (DC) and alternating current (AC) motors. The alternating current types are then subdivided into single-phase and different polyphase designs and, of course, the size or capability of the motor is always an all-important issue. But, the power output doesn't tell us enough; we must also have data pertaining to speed and torque and, speaking of torque, a motor cannot render useful service if it won't start; therefore, specific knowledge about its starting torque is always a matter of priority.

TOC

Electric motor generalities 1
Early discoveries 2
The quest for continuous rotary motion 3
Basic motor action 5
The electric motor as an energy converter 7
Motor graphs 8
Motor nomenclature 9
Horsepower rating of electric motors 1 1
Motor classification 12
Describing performance of electric motors 13
Illustrations pertaining to motors 13
Measuring speed 15
Applying 'hand-rules' to motors 17
Force, current and flux - the orthogonal relationship 18
Counter-e.m.f. Electric motors in the quest for perpetual motion 22
Idealized concept of energy conversion 23
Measurement pitfalls 26
The electric vehicle 26
Things to keep in mind about motors 31
2 Practical aspects of DC motors 32
Background of DC motors 32
The homopolar motor 33
The AC involvement in DC motors 34
A practical view of armature reaction 36
The role of residual magnetism 38
The DC shunt motor 39
The DC permanent magnet motor 42
Paradoxes in DC motor theory 44
Operation of the DC servo motor 47
The motor characteristic of the DC watthour meter 49
The DC series motor 51
The DC compound motor 53
Motor and generator performance in the same machine 54
Reversing the rotation of DC motors 56
Practical use of counter-e.m.f. 57
Flexible control of permanent magnet motors 59
The grey area of DC and AC motors 60 3
Practical aspects of AC motors 62
The great induction motor dilemma 63
Practical aspects of the single-phase induction motor 63
Split-phase suiting techniques for induction motors 65
Types of single-phase AC motors 66
The synchronous motor 68 Shaded-pole motors 72
The hysteresis motor 73
The reluctance motor 75
The wound-rotor induction motor 76
The double squirrel-cage induction motor 80
Speed control of AC motors 82
The consequent-pole AC motor 82
Speed selection by pole modification 84
The universal motor 87
Rotation reversal in AC motors 88
Non-sinusoidal waveforms applied to AC motors 91
Power input and power factor in three-phase induction motors 94
Unusual motor behaviour % 4 Practical projects 99
Experimental aspects of electric motors 99
Considerations in suiting electric motors 99
High starting-torque from a small capacitor 101
Gentle surt-up of AC motors 103
An easy starring technique for three-phase induction motors 104
Altering the characteristics of the sencs motor 105
Phase transformation for motor testing 107
Digiully-generated polyphase waveforms 108
Synchro-system experiments 109
Operating AC motors from 50 Hi or 60 Hz lines 112
Changing the function of a dynamo 1 13
Dynamic braking of induction motors 115
Speed control of fan motors 1 18
Speed control with and without speed-regulation 1 18
Practical aspects of the brushless DC motor 1 20
Improving performance of stepping motors 122
Custom-designing of stepping motors 122
Electronic technique for eliminating the centrifugal switch 1 24
Some motor drive techniques 124
1C control system for permanent magnet DC motors 128
IC control system for brushless DC motor 1 30
IC energy-saving system for induction motors 132
DC permanent magnet motor for electric vehicles 133
Switched reluctance motor 135
Reliability 136 5
Practical problems 138
Dealing with motor mathematics 138
Feeder line as part of the motor circuit 138
Internal power in a permanent magnet DC motor 139
Stray power in a permanent magnet DC motor 1 40
Power determinations from prony-brakc measurements 141
Compound motor speed calculations 142
Speed regulation of DC and AC motors 1 44
Torque calculation of DC series motor 145
Efficiency of DC shunt motor 145
Starting resistance for permanent magnet DC motor 146
Power requirement from electric vehicle motor 147
Speed vs. load for DC shunt motor 1 48
Speed vs. load for DC series motor 149
Synchronous speed calculations 150
Light-load behaviour of induction motor 151
Using wattmeter data for evaluating induction motor performance 1 52
Speed of wound-rotor induction motor vs. rotor resistance 153
Using 50 Hz motors on 60 Hz lines and vice-versa 1 54 Interpreting data for polyphase motors 154
Capacitor calculation for unity power factor 155
Synchronous motor calculations for power factor correction 156
Transformer simulation of induction motor 1 57
Two-wattmeter data for induction motor calculations 1 58
Calculations for induction-generator action from a motor 159