NCCER Electrical L2/M2

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NCCER Electrical L2/M2

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  1. Objectives

    Slide 2 - Objectives

    • When trainees have completed this lesson, they should be able to do the following:
    • 1. Define the following terms:
    • 2. Describe the various types of motor enclosures.
    • 3. Explain the relationships among speed, frequency, and the number of poles in a three-phase induction motor.
    • 4. Define percent slip and speed regulation.
    • 5. Explain how the direction of a three-phase motor is changed.
    • 6. Describe the component parts and operating characteristics of a three-phase wound-rotor induction motor.
    • Motors: Theory and Application 26202-14
    • Controller
    • Interrupting rating
    • Overcurrent
    • Rated full-load speed
    • Duty cycle
    • Thermal protection
    • Overload
    • Rated horsepower
    • Full-load amps
    • NEMA design letter
    • Power factor
    • Service factor
  2. Objectives and Performance Tasks

    Slide 3 - Objectives and Performance Tasks

    • 7. Describe the component parts and operating characteristics of a three-phase synchronous motor.
    • 8. Describe the design and operating characteristics of various DC motors.
    • 9. Describe the methods for determining various motor connections.
    • 10. Describe general motor protection requirements as delineated in the National Electrical Code® (NEC®).
    • Define the braking requirements for AC and DC motors.
    • Performance Tasks
    • 1. Collect data from a motor nameplate.
    • 2. Identify various types of motors and their application(s).
    • 3. Connect the terminals for a dual-voltage motor.
    • Motors: Theory and Application 26202-14
  3. 1.0.0 – 2.0.0

    Slide 4 - 1.0.0 – 2.0.0

    • Motors: Theory and Application 26202-14
    • Introduction; DC Motor Principles
    • • Magnetic lines of force are continuous and form closed loops.
    • • Magnetic lines do not cross.
    • • Like forces repel, while unlike forces attract.
  4. 2.1.0

    Slide 5 - 2.1.0

    • Motors: Theory and Application 26202-14
    • DC Motor Components
    • • The armature is a movable electromagnet located between the poles of another fixed magnet.
    • • The interaction between the two magnetic fields creates motor action.
  5. 2.1.0

    Slide 6 - 2.1.0

    • Motors: Theory and Application 26202-14
    • Motor Action
    • • When a conductor is placed in another magnetic field, the two fields can react to produce motor action.
    • • The conductor must be perpendicular to the magnetic field to achieve the maximum reaction.
  6. 2.1.0

    Slide 7 - 2.1.0

    • Motors: Theory and Application 26202-14
    • Torque
    • • Torque is produced by mounting a loop in a magnetic field.
    • • Current is applied and the flux lines interact, causing the loop to act like a lever with a force pushing on its two sides in opposite directions. This results in a turning force known as torque.
  7. 2.1.0

    Slide 8 - 2.1.0

    • Motors: Theory and Application 26202-14
    • Single-Loop Armature DC Motor
    • • To produce rotation, the armature must be kept moving in the same direction by reversing the direction of current for every 180 degrees of rotation.
    • • This switching action is provided by a device known as a commutator.
  8. 2.1.0

    Slide 9 - 2.1.0

    • Motors: Theory and Application 26202-14
    • Brushes, Brush Rigging, and Commutator Connections
    • • A brush provides a connection between the movable commutator and the stationary power source.
    • • Various types of brushes and commutators are used in DC motors.
  9. 2.1.0

    Slide 10 - 2.1.0

    • Motors: Theory and Application 26202-14
    • Self-Starting Motor
    • • If the armature stops in the middle of switching, the motor will not restart without turning the armature.
    • • A self-starting motor overcomes this by using multiple coils and commutator segments. Regardless of where the armature stops, there is always a path for current to restart the motor.
  10. 2.2.0

    Slide 11 - 2.2.0

    • Motors: Theory and Application 26202-14
    • The Neutral Plane
    • The neutral plane represents the point in the armature rotation where there is no interaction between the magnetic fields.
  11. 2.2.0

    Slide 12 - 2.2.0

    • Motors: Theory and Application 26202-14
    • Neutral Plane in a Single-Loop DC Motor
    • The force of inertia tends to push the armature past the neutral plane so the motor continues to operate. However, the inconsistent torque levels result in erratic operation and prevent the motor from being self-starting.
  12. 2.2.0

    Slide 13 - 2.2.0

    • Motors: Theory and Application 26202-14
    • Understanding the Theory of Torque
  13. 2.3.0

    Slide 14 - 2.3.0

    • Motors: Theory and Application 26202-14
    • Two-Loop DC Motors
    • • When an armature contains two loops at right angles, one loop is in the neutral plane while the other is in a position of maximum torque.
    • • This type of motor is self-starting and operates less erratically than a single-loop motor.
  14. 2.4.0

    Slide 15 - 2.4.0

    • Motors: Theory and Application 26202-14
    • Armature Reaction
    • • Armature reaction is caused by the interaction of the magnetic fields from the field magnets and the armature.
    • • The resultant field shifts the neutral plane of the motor.
  15. 2.4.0

    Slide 16 - 2.4.0

    • Motors: Theory and Application 26202-14
    • Interpoles
    • Armature reaction can be overcome by installing interpole windings.
  16. 2.5.0

    Slide 17 - 2.5.0

    • Motors: Theory and Application 26202-14
    • Counter-Electromotive Force (CEMF)
    • • Counter-electromotive force (CEMF) is generated by the action of the armature windings cutting the lines of force of the field poles.
    • • The value of CEMF depends on the field strength and the armature speed.
  17. 2.5.0

    Slide 18 - 2.5.0

    • Motors: Theory and Application 26202-14
    • No CEMF
    • • CEMF is necessary for proper motor operation and reduces the armature current to a low enough level to drive the motor without excessive heating.
    • • If the armature stalls and no CEMF is produced, the motor draws too much current and becomes overheated.
  18. 2.6.0

    Slide 19 - 2.6.0

    • Motors: Theory and Application 26202-14
    • Starting Resistance
    • • Large DC motors require the addition of a starting resistance to limit the current until CEMF is produced by the motor operation.
    • • A starting resistance typically limits the current to 1.5 times the full-load amps (FLA).
    • • After starting, the resistance is removed from the circuit.
  19. 3.0.0

    Slide 20 - 3.0.0

    • Motors: Theory and Application 26202-14
    • Types of DC Motors
    • • A series motor has the field coils connected in series with the armature (rotor) winding.
    • • A shunt motor has the field coils connected in parallel with the armature (rotor) winding.
    • • A compound motor has both a series- and a shunt-connected field.
  20. 3.1.0 – 3.1.3

    Slide 21 - 3.1.0 – 3.1.3

    • Motors: Theory and Application 26202-14
    • Shunt Motors
    • • The current through a DC shunt motor varies depending on the load (the larger the load, the larger the current, and vice versa), and this results in minor speed changes.
    • • Shunt motors have excellent speed control.
    • • Shunt motors do not develop as much starting torque as series motors and are generally used with smaller loads.
  21. 3.2.0 – 3.2.2

    Slide 22 - 3.2.0 – 3.2.2

    • Motors: Theory and Application 26202-14
    • Series Motors
    • • DC series motors are used in applications requiring large amounts of starting torque, such as cranes.
    • • The speed control of a series motor can be improved with the addition of a motor controller.
  22. 3.3.0 – 3.3.3

    Slide 23 - 3.3.0 – 3.3.3

    • Motors: Theory and Application 26202-14
    • Compound Motors
    • • DC compound motors are used to provide both high starting torque and constant speed under load.
    • • Compound motors contain a shunt and a series winding on each field pole.
  23. 3.4.0 – 3.5.0

    Slide 24 - 3.4.0 – 3.5.0

    • Motors: Theory and Application 26202-14
    • Operating Characteristics of a Typical DC Shunt Motor
    • Note that the speed of a DC shunt motor is fairly consistent up to 150% of the rated capacity.
  24. 3.4.0 – 3.5.0

    Slide 25 - 3.4.0 – 3.5.0

    • Motors: Theory and Application 26202-14
    • Operating Characteristics of a Typical Series Motor
    • Note that the speed of a series DC motor varies greatly with the applied load.
  25. 3.4.0 – 3.5.0

    Slide 26 - 3.4.0 – 3.5.0

    • Motors: Theory and Application 26202-14
    • Operating Characteristics of a Typical DC Compound Motor
    • A compound DC motor provides better starting torque than a shunt motor and better speed control than a series motor.
  26. 4.0.0 – 4.1.3

    Slide 27 - 4.0.0 – 4.1.3

    • Motors: Theory and Application 26202-14
    • Alternating Current Motors
    • • Single-phase motors are typically limited to fractional-horsepower applications, such as fans, appliances, and other low-load devices.
    • • Polyphase motors are used to drive large machinery such as pumps and compressors. The stator windings are set up to create rotating magnetic fields that act on the rotor to operate the motor.
  27. 4.2.0

    Slide 28 - 4.2.0

    • Motors: Theory and Application 26202-14
    • Three-Phase Induction Motors
    • • In induction motors, the rotor currents are supplied by electromagnetic induction. The stator windings connect to three-phase power to produce a rotating magnetic field.
    • • There are two main types of three-phase induction motors: the squirrel cage motor and the wound rotor motor.
  28. 4.2.1

    Slide 29 - 4.2.1

    • Motors: Theory and Application 26202-14
    • Squirrel Cage Induction Motor
    • • The squirrel cage is the most popular rotor in use.
    • • Because they operate on induction, squirrel cage rotors have no brushes or slip rings, and consist of a stator and a rotor in a cast frame with bearings on either end.
  29. 4.2.1

    Slide 30 - 4.2.1

    • Motors: Theory and Application 26202-14
    • Squirrel Cage Rotor
    • • A standard squirrel cage motor is used to drive loads that require variable torque at a consistent speed with high full-load efficiency.
    • • If a load requires extra torque when starting, a squirrel cage rotor can include both starting and running configurations. This is known as a double squirrel cage rotor.
  30. 4.2.2 – 4.2.7

    Slide 31 - 4.2.2 – 4.2.7

    • Motors: Theory and Application 26202-14
    • Wound Rotor Induction Motor
    • • Wound rotor windings are usually connected to slip rings mounted on the rotor shaft. They are used with brushes to provide an electromechanical connection to the rotor.
    • • A variable resistor can be used to limit the resistance when starting. Wound rotor motors are often used for applications that require frequent starts without overheating the motor.
  31. 4.2.2 – 4.2.7

    Slide 32 - 4.2.2 – 4.2.7

    • Motors: Theory and Application 26202-14
    • Wound Rotor Motor Circuit
    • • A resistance can also be used to provide adjustable speed control.
    • • Wound rotor motors provide good running characteristics but have higher maintenance requirements than squirrel cage motors.
  32. 4.2.2 – 4.2.7

    Slide 33 - 4.2.2 – 4.2.7

    • Motors: Theory and Application 26202-14
    • Typical Torque-Speed Curve
    • • In an induction motor, the rotor always operates at less than synchronous (full) speed due to the mechanical load and friction. This is known as slip.
    • • The full-load slip may reduce the speed of the motor by up to 10%.
  33. 4.2.8

    Slide 34 - 4.2.8

    • Motors: Theory and Application 26202-14
    • Overload Condition
    • • The motor torque climbs after starting until it reaches its full-rated load and then continues to climb until it reaches the pullout torque.
    • • If pushed beyond the pullout torque, the motor will stall. An example of this is when a circular saw stalls during cutting.
  34. 4.2.9 – 4.2.10

    Slide 35 - 4.2.9 – 4.2.10

    • Motors: Theory and Application 26202-14
    • Power Factor and Speed Control
    • • The power factor of a squirrel cage induction motor is best at high-load conditions and worst at no-/low-load conditions.
    • • Squirrel cage motors are either used in constant-speed applications or where speed control can be provided by means of variable frequency drives.
  35. 4.2.11

    Slide 36 - 4.2.11

    • Motors: Theory and Application 26202-14
    • Reversing Rotation
    • • The direction of rotation of a three-phase induction motor can be changed by reversing two of the three incoming leads.
    • • Always connect leads carefully to endure proper rotation.
  36. 4.3.0 – 4.3.3

    Slide 37 - 4.3.0 – 4.3.3

    • Motors: Theory and Application 26202-14
    • Synchronous Motors
    • • A synchronous motor operates at synchronous speed from no-load to full-load conditions and can be used to correct a low power factor.
    • • The rotor is energized by a DC source separate from the three-phase AC that powers the stator windings.
    • • An amortisseur winding is used to overcome the lack of starting torque.
  37. 4.3.0 – 4.3.3

    Slide 38 - 4.3.0 – 4.3.3

    • Motors: Theory and Application 26202-14
    • Simplification of a Synchronous Motor
    • The rotor windings are constructed so that the north and south poles will lock in with the revolving field produced by the DC motor.
  38. 4.3.0 – 4.3.3

    Slide 39 - 4.3.0 – 4.3.3

    • Motors: Theory and Application 26202-14
    • Pole Assembly
    • • The rotor field windings connect to slip rings on the rotor shaft and the field current is supplied through brushes to the field windings.
    • • When a synchronous motor is started, current is applied to the stator windings and induced in the amortisseur windings.
  39. 4.3.4

    Slide 40 - 4.3.4

    • Motors: Theory and Application 26202-14
    • Rotor Field Excitation
    • • The rotor must be excited from an external DC source.
    • • As the DC field strength is increased, the power factor can approach unity or 100%.
  40. 4.3.5 – 4.3.6

    Slide 41 - 4.3.5 – 4.3.6

    • Motors: Theory and Application 26202-14
    • Synchronous Motor Pullout and Torque Angle
    • • Conditions that may cause a motor to lose synchronism (go out of step) include excessive loads, reduced supply voltage, and lost/low motor excitation.
    • • While the motor is running, the two rotating fields will align and the rotor pole will lag the stator pole by a predetermined angle known as the torque angle.
  41. 4.4.0 – 4.4.1

    Slide 42 - 4.4.0 – 4.4.1

    • Motors: Theory and Application 26202-14
    • Single-Phase AC Motors
    • • Single-phase AC motors are commonly used in various small and large household appliances.
    • • A single-phase AC induction motor has a stationary stator that alternates polarity between poles. Voltage is induced in the rotor and an outside force is required to begin rotation (typically a starting circuit).
  42. 4.4.2

    Slide 43 - 4.4.2

    • Motors: Theory and Application 26202-14
    • Split-Phase Induction Motor
    • • A split-phase motor has both a starting winding and a main (running) winding.
    • • When the rotor reaches about 75% of rated speed, the starting winding drops out of the circuit and the motor continues to run using the main winding.
  43. 4.4.3

    Slide 44 - 4.4.3

    • Motors: Theory and Application 26202-14
    • Capacitor-Type Induction Motor
    • • Capacitor-type motors are similar to split-phase motors but are able to develop a larger starting torque.
    • • The capacitor is located on top of the motor and provides about four times the rated torque of the motor.
  44. 4.4.3

    Slide 45 - 4.4.3

    • Motors: Theory and Application 26202-14
    • Capacitor-Start Motor Schematic
    • • When a capacitor is placed in series with the starting winding of a single-phase motor, it is called a capacitor-start motor.
    • • Once the motor is up to speed, the start winding is disconnected and the motor operates in the same way as a split-phase motor.
  45. 4.4.3

    Slide 46 - 4.4.3

    • Motors: Theory and Application 26202-14
    • Torque-Slip Curves
  46. 4.4.3

    Slide 47 - 4.4.3

    • Motors: Theory and Application 26202-14
    • Capacitor-Start, Capacitor-Run Motor Schematic
    • • A capacitor-run motor leaves the capacitor in the circuit continuously and while it does not provide a high starting torque, it does offer improved running characteristics.
    • • A capacitor-start, capacitor-run motor uses two capacitors to provide both high starting torque and improved running characteristics.
  47. 4.4.4 – 4.4.5

    Slide 48 - 4.4.4 – 4.4.5

    • Motors: Theory and Application 26202-14
    • Shaded-Pole Induction Motor
    • Shaded-pole motors use field coils with copper shading coils to produce a rotating magnetic field.
  48. 4.4.4 – 4.4.5

    Slide 49 - 4.4.4 – 4.4.5

    • Motors: Theory and Application 26202-14
    • Two-Pole Shaded-Pole Motor
    • • Shaded-pole motors are low-horsepower motors used in applications such as small fans.
    • • They are simple and inexpensive, but provide low starting torque and efficiency, and are noisy during operation.
  49. 5.0.0 – 5.1.0

    Slide 50 - 5.0.0 – 5.1.0

    • Motors: Theory and Application 26202-14
    • Multiple-Speed Induction Motors
    • • Motor speed is dependent on the power supply frequency and the number of poles. The speed is normally increased by changing the number of poles.
    • • Speed control is normally accomplished in a motor controller external to the motor.
  50. 5.2.0

    Slide 51 - 5.2.0

    • Motors: Theory and Application 26202-14
    • Consequent-Pole Motor
    • • A consequent-pole motor has two speeds.
    • • At high speed, two poles per phase are used to provide 3,600 rpm.
  51. 5.2.0

    Slide 52 - 5.2.0

    • Motors: Theory and Application 26202-14
    • Low-Speed Consequent-Pole Motor
    • • The connections can be changed to provide four magnetic north poles and consequently, four south poles.
    • • The four poles per phase produce a rotating magnetic field at 1,800 rpm.
  52. 5.2.0

    Slide 53 - 5.2.0

    • Motors: Theory and Application 26202-14
    • Single-Phase Consequent-Pole Motor
    • • Parallel connections can be used to create four opposite consequent poles.
    • • Constant-horsepower motors are used to drive machine tools, while constant-torque motors are used to drive pumps, compressors, and blowers. Variable-torque, variable-horsepower motors are used in fans and air conditioners.
  53. 6.0.0 – 6.1.0

    Slide 54 - 6.0.0 – 6.1.0

    • Motors: Theory and Application 26202-14
    • Variable-Speed Drives
    • • A constant-torque load requires the same torque regardless of speed, but the horsepower increases with the speed.
    • • A variable-torque load requires less torque and horsepower at lower speeds.
    • • A constant-horsepower load requires more torque at lower speeds, but the horsepower remains constant.
  54. 6.2.0

    Slide 55 - 6.2.0

    • Motors: Theory and Application 26202-14
    • Motor Considerations
    • • A machine with positive torque and positive speed or negative torque and negative speed functions as a motor.
    • • A machine with positive torque and negative speed or negative torque and positive speed functions as a brake or generator.
  55. 6.2.1 – 6.2.2

    Slide 56 - 6.2.1 – 6.2.2

    • Motors: Theory and Application 26202-14
    • Typical Torque-Speed Curves
    • • When the stator leads are reversed, the motor switches between acting as a generator and acting as a brake in quadrants 2 and 4.
    • • It always acts as a motor in quadrants 1 and 3.
  56. 6.2.1 – 6.2.2

    Slide 57 - 6.2.1 – 6.2.2

    • Motors: Theory and Application 26202-14
    • Four-Quadrant Operation for a DC Motor
    • • A DC shunt motor operates in the same quadrants, with the dotted line representing reversed armature leads.
    • • When using variable-speed drive systems, motor heating must be monitored to ensure effective cooling.
  57. 6.3.0 – 6.3.4

    Slide 58 - 6.3.0 – 6.3.4

    • Motors: Theory and Application 26202-14
    • Motor Speed Control
    • • The torque-speed characteristic can be shifted by varying the voltage applied to the field winding or the armature.
    • • As the field voltage is increased, the motor slows down.
    • • As the armature voltage is increased, the motor speeds up.
    • Performance Task
    • This session will conclude with trainees identifying various types of motors and their application(s).
    • Next Sessions…
    • Motor Enclosures
  58. 7.0.0 – 7.2.0

    Slide 59 - 7.0.0 – 7.2.0

    • Motors: Theory and Application 26202-14
    • Motor Enclosures
    • Motor enclosures are classified by the National Electrical Manufacturers Association (NEMA) according to the degree of environmental protection provided and the method of cooling.
  59. 8.0.0 – 8.2.0

    Slide 60 - 8.0.0 – 8.2.0

    • Motors: Theory and Application 26202-14
    • NEMA Frame Designations
    • • NEMA developed standard frame sizes to ensure the interchangeability of motors built by different manufacturers.
    • • The distance from the motor feet to the shaft centerline is known as the D dimension.
  60. 8.0.0 – 8.2.0

    Slide 61 - 8.0.0 – 8.2.0

    • Motors: Theory and Application 26202-14
    • Lettering of Dimension Sheets for Foot-Mounted Machines (Side View)
    • • The center-to-center distance between front and back feet is known as the 2F dimension.
    • • The exposed shaft distance is called the N-W dimension.
    • • Manufacturer tables are available to correlate frame sizes with actual dimensions.
  61. 8.0.0 – 8.2.0

    Slide 62 - 8.0.0 – 8.2.0

    • Motors: Theory and Application 26202-14
    • Frame Dimension Chart
  62. 9.0.0 – 9.1.19

    Slide 63 - 9.0.0 – 9.1.19

    • Motors: Theory and Application 26202-14
    • Motor Ratings and Nameplate Data
    • • NEC Section 430.7 and NEMA Standards MG-1 and MG-2 list the requirements for motor nameplate data.
    • • The rated voltage on the nameplate is typically lower than that supplied by the electrical system.
  63. 9.0.0 – 9.1.19

    Slide 64 - 9.0.0 – 9.1.19

    • Motors: Theory and Application 26202-14
    • Induction Motor Voltages
    • • Motor manufacturers assume there will be a 20V drop from the transformer down to the motor terminals.
    • • The nameplate voltage shows the most effective voltage for motor operation. Operation at other voltages may impact motor performance and service life.
  64. 9.0.0 – 9.1.19

    Slide 65 - 9.0.0 – 9.1.19

    • Motors: Theory and Application 26202-14
    • High-Voltage and Low-Voltage Connection Diagrams Shown on Motor Nameplate
    • • Some nameplates list both low-voltage and high-voltage connections (e.g., 230/460V).
    • • Motor nameplates for dual-voltage units typically include a connection diagram.
  65. 9.0.0 – 9.1.19

    Slide 66 - 9.0.0 – 9.1.19

    • Motors: Theory and Application 26202-14
    • Motor Operation
    • • The full-load amps (FLA) rating on a motor nameplate represents the current the motor will draw at the nameplate horsepower, frequency, and voltage.
    • • The motor FLA is used to size the cable and overload/overcurrent devices in the circuit, but may vary depending on the actual voltage and frequency of the supply source.
  66. 9.0.0 – 9.1.19

    Slide 67 - 9.0.0 – 9.1.19

    • Motors: Theory and Application 26202-14
    • Typical Currents for 220V, 60-Cycle Squirrel Cage Motors
    • • NEMA design letters define the starting torque characteristics of an induction motor. It is essential to match the design letter to the application. About 80% of industrial motors are NEMA Design B.
    • • The motor starting current is typically five to seven times the rated full-load current.
  67. 9.0.0 – 9.1.19

    Slide 68 - 9.0.0 – 9.1.19

    • Motors: Theory and Application 26202-14
    • Nameplate Showing Insulation Class
    • • Premature failure of motor insulation is a leading cause of motor failure.
    • • NEMA specifies four different insulation classes for motors: A, B, F, and H. Class B is the most common type.
    • • The service factor indicates the amount of overload a motor can withstand. A typical service factor is 1.15.
  68. 9.0.0 – 9.1.19

    Slide 69 - 9.0.0 – 9.1.19

    • Motors: Theory and Application 26202-14
    • Locked-Rotor Code Letters
    • • The high current a motor draws on startup is called the inrush or locked-rotor current.
    • • The kVA code letter on the motor nameplate corresponds to a specific value of inrush current.
  69. 9.0.0 – 9.1.19

    Slide 70 - 9.0.0 – 9.1.19

    • Motors: Theory and Application 26202-14
    • Nameplate Showing Bearings, Horsepower, and Amperage
    • • Polyphase motors require anti-friction or sleeve bearings (typically found in motors above 500hp).
    • • The rated amperage is the full-load current required to produce full-rated horsepower at the motor’s rated voltage and frequency.
    • • The power factor (pf) measures efficiency and represents the ratio of active power to apparent power as measured on a meter.
  70. 9.2.0 – 9.2.2

    Slide 71 - 9.2.0 – 9.2.2

    • Motors: Theory and Application 26202-14
    • Motor Protection
    • • Fuses are normally used for motor overload protection.
    • • Where other devices such as trip coils or relays are used, the number of units can be determined using the data shown here.
  71. 9.2.0 – 9.2.2

    Slide 72 - 9.2.0 – 9.2.2

    • Motors: Theory and Application 26202-14
    • Duty Cycle Service
    • Protection for motors against overcurrents and ground faults can be determined using the data shown here.
  72. 9.2.0 – 9.2.2

    Slide 73 - 9.2.0 – 9.2.2

    • Motors: Theory and Application 26202-14
    • Motor Protection
    • • Thermal protectors are used to protect a motor from overloads and starting failures. All motors operating over 1,000V require a thermal protector.
    • • Protection for motors with special duty requirements can be determined using the data shown here.
    • Performance Task
    • This session will conclude with trainees collecting data from a motor nameplate.
    • Next Session…
    • Connections and Terminal Markings for AC Motors
  73. 10.0.0

    Slide 74 - 10.0.0

    • Motors: Theory and Application 26202-14
    • Connections and Terminal Markings for AC Motors
    • • In this wye-connected motor, three coils are connected and the other three are isolated.
    • • The leads can be grouped by testing them for continuity.
  74. 10.0.0

    Slide 75 - 10.0.0

    • Motors: Theory and Application 26202-14
    • Dual-Voltage, Three-Phase Delta Connection
    • This delta-connected motor has three sets of two coils each connected together.
  75. 10.1.0

    Slide 76 - 10.1.0

    • Motors: Theory and Application 26202-14
    • Identifying the Terminals of Wye-Connected Motors
    • • It is often necessary to identify the leads when they have worn off on older or unlabeled motors.
    • • To begin, label the three common leads, then test the remaining leads using a DC voltmeter to find the lead with the highest voltage and those with positive and negative polarity.
  76. 10.1.0

    Slide 77 - 10.1.0

    • Motors: Theory and Application 26202-14
    • Battery Hookup for Wye-Connected Motor Lead Identification
  77. 10.2.0

    Slide 78 - 10.2.0

    • Motors: Theory and Application 26202-14
    • Identifying the Terminals of Delta-Connected Motors
    • • To identify the terminals of a delta-connected motor, use an ohmmeter on a low scale to measure the resistance between each of the three leads in one group. The lead that shows the least resistance will be lead 1.
    • • Continue to test the remaining leads using an ohmmeter to identify the leads by measuring their resistance.
  78. 10.2.0

    Slide 79 - 10.2.0

    • Motors: Theory and Application 26202-14
    • Battery Hookup for Delta-Connected Motor Lead Identification
    • Performance Task
    • This session will conclude with trainees connecting the terminals for a dual-voltage motor.
  79. 11.0.0 – 13.0.0

    Slide 80 - 11.0.0 – 13.0.0

    • Motors: Theory and Application 26202-14
    • NEC® Requirements; Braking; Motor Installation
    • Review the NEC® requirements for motors as covered in NEC Articles 430 and 440.
  80. 11.0.0 – 13.0.0

    Slide 81 - 11.0.0 – 13.0.0

    • Motors: Theory and Application 26202-14
    • Summary of Requirements for Motors, Motor Circuits, and Controllers
  81. 11.0.0 – 13.0.0

    Slide 82 - 11.0.0 – 13.0.0

    • Motors: Theory and Application 26202-14
    • Installing Motors
    • • A wet motor must be dried and tested before starting.
    • • Always follow the manufacturer’s instructions when installing motors.
    • • A micrometer can be used to achieve precise alignment during motor installation.
    • Next Session…
    • Wrap Up
  82. Wrap Up

    Slide 83 - Wrap Up

    • 3-2-1
    • 3 – Write 3 important things learned during class
    • 2 – Write 2 questions you have about the material
    • 1 – Write 1 thought you had about the material
    • Motors: Theory and Application 26202-14
  83. Next Session…

    Slide 84 - Next Session…

    • MODULE EXAM
    • Review the complete module to prepare for the module exam. Complete the Module Review as a study aid.
    • Motors: Theory and Application 26202-14