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Electric Motor Maintenance and Troubleshooting, 2nd Edition, 2nd Edition

Book Description

A fully up-to-date, hands-on guide to electric motors

Keep electric motors running at peak performance! Electric Motor Maintenance and Troubleshooting, Second Edition explains in detail how all types of AC and DC motors work. Essential for anyone who needs to buy, install, troubleshoot, maintain, or repair small to industrial-size electric motors, this practical guide contains new information on three-phase motors along with coverage of the latest test instruments.

Drawing on his more than 40 years of experience working with electric motors, expert author Augie Hand provides a wealth of tested procedures to pinpoint and correct any kind of issue. He'll help you decide whether to replace a motor, take it offline for repair, or repair it in place--decisions that can reduce down time. End-of-chapter questions reinforce the material covered in the book. Quickly and accurately diagnose electric motor problems and find effective solutions with help from this fully updated classic.

Electric Motor Maintenance and Troubleshooting, Second Edition covers:

  • Troubleshooting and testing DC machines
  • AC electric motor theory
  • Single-phase motors
  • Three-phase induction motors
  • Troubleshooting less common motors, including synchronous, two-speed one-winding, and multispeed
  • Test instruments and services

Table of Contents

  1. Cover Page
  2. Title Page
  3. Copyright
  4. Dedication
  5. About the Author
  6. Contents
  7. Troubleshooting Single-Phase Motors
  8. Troubleshooting Three-Phase Motors
  9. Troubleshooting the DC Machine
  10. Introduction
  11. Chapter 1 The DC Machine
    1. Basic Electricity as It Applies to Motors
      1. Volts
      2. Resistance
      3. Amperes
      4. Additional Information on Copper Wire
      5. Ohm’s Law
      6. Watt
    2. Magnets and the Magnetic Circuits
      1. The Bar Magnet
      2. The Electromagnet
      3. The Magnetic Pole
    3. Ampere Turns
      1. The Magnetic Circuit
      2. Magnetic Saturation
      3. Magnetic Balance
      4. Neutral Position in the Stator
    4. Circuits of the DC Machine
    5. Rules for Generating Direct Current
    6. The Shunt Generator
      1. The Armature and Interpoles
      2. The Shunt Field
      3. Operation of the Self-Excited Shunt Generator
      4. Shunt Generator Control
    7. The Series Generator
      1. Operation of the Self-Excited Series Generator
    8. The Compound Generator
      1. The Armature and Interpoles
      2. The Series Field
      3. The Shunt Field
      4. Operation of the Self-Excited Compound Generator
      5. Compound Generator Control
      6. The Cumulative Compound Connection (Generator)
      7. The Differential Compound Connection (Generator)
      8. Series Field Connections for a Motor and a Generator
      9. Special-Purpose Machine Connections
    9. The DC Arc Welder
      1. Operation of the DC Welder Generator
      2. Operation of the Welder’s Reactor
    10. Interpoles
      1. Operation of Interpoles
      2. The Compensating Winding
    11. Operation of a DC Motor
      1. One Armature Conductor in a Generator as It Passes Two Poles
      2. One Armature Conductor in a Motor as It Passes Two Poles
      3. Counter-voltage
      4. Counter-voltage Compared to Charging a Battery
      5. Counter-voltage in a Motor Armature
      6. Base Speed
      7. Below Base Speed
      8. Above Base Speed
      9. Torque of the DC Motor
    12. The Shunt Motor
      1. The Armature and Interpoles
      2. The Shunt Field
      3. Operation of the Shunt DC Motor
    13. The Permanent Magnet DC Motor
      1. Operation of the Permanent Magnet Motor
      2. Restoring Magnetism
    14. The Series Motor
      1. Operation of the Series Motor
    15. The Compound DC Motor
      1. The Armature and Interpoles
      2. The Shunt Field
      3. The Series Field
      4. Operation of the Compound Motor Connected Cumulative Compound
    16. The Stabilized Shunt Motor
    17. Speed Control for a Compound DC Motor
      1. Armature Control for Starting and for Below Base Speed
      2. Shunt Field Control for Starting and for Above Base Speed
      3. The Differential Connection (Motor)
    18. Armature Components
      1. Commutator
      2. Commutator Film
      3. Armature Windings
      4. Equalizer Shunts
      5. Laminated Iron
    19. Chapter 1 Review
  12. Chapter 2 Troubleshooting and Testing the DC Machine
    1. Armature Problems
      1. Burned Commutator Bars
      2. Dirty Commutator
      3. Dead Spots from an Open Armature Coil
      4. Open Equalizer
      5. Stalled Motor
      6. Control and Load Problems
      7. Brushes
    2. Brush Problems
      1. Conduction Zone
      2. Spiral Groove
      3. Multiple Brushes
      4. Brush Box and Commutator Spacing
      5. Distance Between Brushes
      6. Brush Holder Alignment
      7. Spring Tension
      8. Brush Shunts
      9. Side Wear
      10. Uneven Commutator Segments
      11. Brush Dusting
      12. Low Load Current
      13. Silicone Vapor and Adverse Ambient Conditions
      14. Seating Brushes
    3. Neutral Location in the Stator and Armature
      1. Setting Neutral in a Motor
      2. Black Band Adjustment
      3. Setting Neutral in a Generator
      4. Restoring Residual Magnetism After Setting Neutral
      5. Overheated Motor
    4. Field Testing the DC Machine
      1. Field Testing the Armature
      2. Field Testing for Grounds in the Armature Circuit with an Ohmmeter
      3. Field Testing the Shunt Field
      4. Field Testing the Series Field
    5. Locating Problems in the DC Machine
      1. Locating Problems in the Armature
      2. Locating a Grounded Interpole with AC and a Clamp-on Ammeter
      3. Locating a Shorted Interpole Using the AC Voltage Drop Test
      4. Locating a Shorted Interpole Using the Smoke Test
    6. Locating Problems in the Shunt Field
      1. The Comparison Test
      2. Needle Probes
      3. Variations in the Shunt Field Circuitry
    7. Drawing Simple Schematics of a Shunt Field
      1. Drawing a Diagram of a Two-Circuit Shunt Field
      2. Drawing a Diagram of a Two-Circuit, Two-Coils-per-Pole Shunt Field
      3. Ground to the Frame Symptom
      4. Shorted Turns in the Shunt Field Symptoms
      5. Shunt Field with an Open Circuit
      6. Shunt Field Shorted to the Series Field Symptoms
    8. Locating Problems in the Series Field
      1. Ground to Frame Symptoms
      2. Shorted Turns in the Series Field Symptoms
      3. Locating an Open Circuit in Series Field
    9. Identifying Leads of a Compound DC Motor with an Ohmmeter
    10. Chapter 2 Review
  13. Chapter 3 Electric Motor theory
    1. AC Terminology
      1. Generating Alternating Current
      2. Cycles and Hertz
      3. Electrical Degrees and Time
      4. Electrical Degrees and Mechanical Degrees
      5. Degrees and Location
      6. Two-Phase Power
      7. Two-Phase Rotating Magnetic Field
      8. Revolutions per Minute, Poles, and Hertz
      9. The Single-Phase Alternator
      10. Current, Ampere, Power, and Reactive Terms
    2. Inductive Reactance
      1. Impedance
      2. Inductive Reactance and Counter-voltage
      3. Power Factor
      4. Unity Power Factor
      5. Magnetizing Amperes and Lagging Power Factor
      6. Power Factor in Motors
      7. Low Power Factor Concerns
      8. Inductive Reactance and Hertz Change
      9. Formula for 50-Hz to 60-Hz Power Change
      10. Impedance in a Three-Phase Winding
    3. Capacitance and Capacitive Reactance
      1. Capacitor Function
      2. Capacitor Value
      3. Capacitors for Single-Phase Motors
    4. Oil-Filled Capacitor
      1. Oil-Filled Capacitor in Single-Phase Motors
      2. Oil-Filled Capacitor Components
      3. Oil-Filled Capacitor Connection in a Two-Value Capacitor Single-Phase Motor
      4. Mounting the Oil-Filled Capacitor
    5. Electrolytic Capacitors
      1. Electrolytic Capacitor Function in the Capacitor-Start Motor
      2. Electrolytic Capacitor Components
      3. Electrolytic Capacitor and Start-Winding Connections
      4. Parallel Electrolytic Capacitor Connection
      5. Series Electrolytic Capacitor Connection
      6. Testing the Electrolytic Capacitor
    6. Capacitor Test Formula
      1. Determining the Right Size Capacitor
      2. Operation of the Single-Phase Capacitor-Start Motor
      3. Transformer Theory
      4. Transformer Components
      5. Transformer Function
      6. Transformer Rating
      7. Solder Gun Transformer
    7. The Squirrel Cage Rotor
      1. Current Flow in Stator Coils
      2. Function of the Squirrel Cage Rotor
      3. Rotor Hertz and Amperes
      4. Slip, Hertz, and Motor Speed
      5. Synchronous Speed and Zero Torque
      6. Rotor Bar Stress
      7. Broken Rotor Bars
      8. Cracked End Rings
      9. Misaligned Rotor Iron
    8. Chapter 3 Review
  14. Chapter 4 The Single-Phase Motor
    1. Shaded-Pole Motor
      1. Multispeed Shaded-Pole Motor
      2. Troubleshooting the Shaded-Pole Motor
    2. Split-Phase Motor
      1. Components of the Split-Phase Motor
      2. Operation of the Split-Phase Motor
      3. Troubleshooting the Split-Phase Motor
    3. Capacitor Motors
      1. The Capacitor-Run Motor
      2. The Capacitor-Start Motor
      3. Two-Value Capacitor Motor (Capacitor-Start, Capacitor-Run Motor)
      4. Capacitor-Start Motor Connections
    4. Thermal Protective Devices
      1. Components of the Bimetal Thermal Protective Devices (for Single-Phase Motors)
      2. Connections and Operation of the Thermal Protective Device
      3. Limitations of Thermal Protective Devices
    5. Alternative Start-Winding Switches
      1. Potential Relay Start Switch
      2. Electronic Start Switch
      3. Time-Delay Electronic Start Switch
      4. Heat-Activated Start Switch
      5. Current Relay Start Switch
    6. Chapter 4 Review
  15. Chapter 5 The Three-Phase Induction Motor
    1. Components of the Three-Phase Motor
      1. Rotor and Fan
      2. Stator Core
      3. Shell and Frame
      4. End Brackets
      5. Bearings
    2. Operation of the Three-Phase Motor
      1. The Rotating Magnetic Field in a Three-Phase Motor
      2. Single-Phase Condition
    3. Amperes and Rotor Bar Design
      1. Phase Angle
      2. Small Rotor Bars
      3. Large Rotor Bars
      4. Code Letter
      5. Torque and Speed
      6. Design Letter
    4. Introduction to Three-Phase Motor Types
      1. The Nine-Lead Induction Motor
      2. Nine-Lead Wye Connection
      3. Nine-Lead Multiple-Wye Connection with T10
      4. Thermal Protector for the Nine-Lead Wye-Connected Motor
      5. Nine-Lead Delta Connection
      6. Multiple-Delta Connection
      7. Twelve-Lead Connection
    5. Multispeed Motors
      1. Single-Winding Two-Speed Motors
      2. Constant-Horsepower Motor
      3. Constant-Torque Motor
      4. Variable-Torque Motor
      5. Multispeed Multiwinding Motor
      6. Two-Speed Two-Winding Motor
    6. Multimode Nine-Lead Three-Phase Motors
      1. Comparing Multimode Motors to Standard Motors
      2. Triple-Mode, Nine-Lead Three-Phase Motor
    7. Identifying the Triple-Mode, Nine-Lead Three-Phase Motor
      1. Quadruple-Mode, Nine-Lead Three-Phase Motor
      2. Identifying the Quadruple-Mode, Nine-Lead Three-Phase Motor
    8. Synchronous Motor
      1. Components of the Synchronous Motor
      2. Operation of the Synchronous Motor
      3. The Synchronous Motor Control
      4. Power Factor Correction with a Synchronous Motor
      5. The Brushless Synchronous Motor
      6. Three-Phase Alternator
      7. Wound Rotor Motor
      8. Components of the Wound Rotor Motor
      9. Operation of the Wound Rotor Motor
      10. Liquid Used for Speed Control
      11. Reversing the Wound Rotor Motor
      12. Wound Rotor Motor Used as a Variable-Voltage Transformer
      13. Wound Rotor Motor Used as a Hertz Changer
      14. The Brushless DC Motor
      15. Components of Brushless DC Motors
      16. Operation of the Brushless DC Motor
    9. Three-Phase Servo Motors
      1. Identifying the Three-Phase Induction Motor
      2. Nine-Lead Dual-Voltage Motors
      3. Three-Lead Motors
      4. Six-Lead Motors
      5. Twelve-Lead Single-Speed Motors
      6. Dual-Voltage Multispeed Motors
      7. European Connections
    10. Chapter 5 Review
  16. Chapter 6 Troubleshooting Three-Phase Motors
    1. The Dual-Voltage Nine-Lead Motor’s Internal Connections
      1. Understanding the Nine-Lead Wye Connection
      2. Understanding the Nine-Lead Delta Connection
      3. Smaller Wire Size with Delta and Multicircuit Winding
    2. Identifying Unmarked Leads in a Nine-Lead Three-Phase Motor
      1. Identifying Unmarked Leads in a Wye Connection
      2. Identifying Unmarked Leads in a Delta Connection
      3. Theory of Unmarked Lead Test
    3. Typical Winding Problems
      1. Shorted Turns
      2. Ground
      3. Phase-to-Phase Short
      4. Open Winding
      5. Burned Windings from Operating on Single Phase
      6. Submerged Motor
      7. Assorted Rotor Problems
    4. When Motors Overheat
      1. Line-Caused Overheating
      2. Operator-Caused Overheating
      3. Control-Caused Overheating
      4. Motor Fault Overheating
      5. Location-Caused Overheating
      6. Maintenance-Caused Overheating
    5. Chapter 6 Review
  17. Chapter 7 Troubleshooting Less Common Motors
    1. Troubleshooting Logic Using Voltage Rules
    2. Troubleshooting Less Common Motors
      1. Troubleshooting Identified Motors
    3. Troubleshooting the Synchronous Motor
      1. The DC Exciter Field and Discharge Resistor
      2. The Amortisseur Winding
      3. Stator Winding
    4. Troubleshooting the Two-Speed One-Winding Motor
    5. Troubleshooting Multispeed Multiwinding Motors
      1. Circulating Current in Multiwinding Multispeed Motors
      2. Rotor Problems in the Multispeed Motor
    6. Testing Motors in Place
      1. Test Instruments for Testing in Place
      2. Core and Rotor Damage
      3. Troubleshooting the Nine-Lead Motor (Wye or Delta) in Place
      4. Visual Check of the Nine-Lead Motor (Wye or Delta)
      5. Testing from Control (Wye or Delta)
      6. Starting the Motor After the Comparison Test from Control
      7. Line/Lead Interchange Test for Uneven Amperes
      8. Recording Motor Faults
    7. Locating Motor Faults
      1. Test Equipment for Locating Motor Faults
      2. Locating Shorted Turns in a Wye-Connected Nine-Lead Motor
      3. Locating Voltage Spike Damage in a Wye-Connected Nine-Lead Motor
      4. Locating Shorted Turns in a Delta-Connected Nine-Lead Motor
      5. Megohmmeter Test for Ground
    8. Bearing Maintenance
      1. Motor Storage Concerns
      2. Bearing Failure Causes
      3. Lubrication Schedule and Bearing Life
      4. Grease Types
      5. Changing Grease Types
      6. Lubrication Procedure
      7. Alternate Lubrication Methods
      8. Gearbox Lubrication
      9. Shielded Bearings
      10. Sealed Bearings
      11. Labyrinth Seal
      12. Bearing Removal
      13. Bearing Installation
      14. Identifying Bearing Breakdown Causes
      15. Specialized Bearing Tools
    9. Sleeve Bearings
    10. Chapter 7 Review
  18. Chapter 8 Test Instruments and Services
    1. Instruments for Initial Testing
      1. Voltmeter
      2. Clamp-on Ammeter
      3. Ohmmeter
      4. Microhmmeter
      5. Tachometer
      6. Megohmmeter
      7. Infrared Gun
      8. Stethoscope
    2. Instruments for In-depth Testing and Scheduled Maintenance
      1. Surge Tester
      2. Rotor Test
      3. Polarization Index Test with a Megohmmeter
      4. Step Voltage Test
      5. High-Potential Test
      6. Power Quality Test Instruments
      7. Vibration Sensors
      8. Laser Alignment
      9. Particle Analysis
    3. Chapter 8 Review
  19. Index