NCCER 10 Flashcards
Single-phasing means the loss of two phases in a running motor.
a. True
b. False
Single-phasing: The loss of a single phase of a polyphase power source for a running motor.
B. False
If the load connected to a motor is increased beyond the motor’s rating, which of the following is most likely to occur?
a. Contact between the rotor and stator
b. Decreased operating temperature
c. Increased operating temperature and decreased motor life
d. Loss of bearing lubrication
C. Increased operating temperature and decreased motor life
An insulation system that, by experience or accepted test, can be shown to have a suitable thermal endurance when operated at a limit- ing temperature of 105°C is a ____.
a. Class A insulation system
b. Class B insulation system
c. Class F insulation system
d. Class H insulation system
a. Class A insulation system
- Class A-Thermal endurance 105°C. Materials used include cotton, paper, cellulose acetate films, enamel-coated wire, and similar organic materials.
- Class B-Thermal endurance of 130°C. Materials include mica, glass fiber.
- Class F-Thermal endurance of 155°C. Materials include mica, glass fiber.
- Class H-Thermal endurance of 180°C. Materials used include mica, glass fiber, silicone elastomer.
Typical materials used in a Class H insulation system include ____.
a. cotton
b. paper
c. cellulose acetate films
d. silicone elastomer
d. silicone elastomer
- Class A-Thermal endurance 105°C. Materials used include cotton, paper, cellulose acetate films, enamel-coated wire, and similar organic materials.
- Class B-Thermal endurance of 130°C. Materials include mica, glass fiber.
- Class F-Thermal endurance of 155°C. Materials include mica, glass fiber.
- Class H-Thermal endurance of 180°C. Materials used include mica, glass fiber, silicone elastomer.
Typical materials used in a Class F insulation system include ____.
a. cotton
b. paper
c. cellulose acetate films
d. mica
d. mica
- Class A-Thermal endurance 105°C. Materials used include cotton, paper, cellulose acetate films, enamel-coated wire, and similar organic materials.
- Class B-Thermal endurance of 130°C. Materials include mica, glass fiber.
- Class F-Thermal endurance of 155°C. Materials include mica, glass fiber.
- Class H-Thermal endurance of 180°C. Materials used include mica, glass fiber, silicone elastomer.
An insulation system that, by experience or accepted test, can be shown to have a suitable thermal endurance when operated at a limiting temperature of 130°C is a ____.
a. Class A insulation system
b. Class B insulation system
c. Class F insulation system
d. Class H insulation system
b. Class B insulation system
- Class A-Thermal endurance 105°C. Materials used include cotton, paper, cellulose acetate films, enamel-coated wire, and similar organic materials.
- Class B-Thermal endurance of 130°C. Materials include mica, glass fiber.
- Class F-Thermal endurance of 155°C. Materials include mica, glass fiber.
- Class H-Thermal endurance of 180°C. Materials used include mica, glass fiber, silicone elastomer.
Motors with two separate winding circuits employ ___.
a. primary resistor starting
b. autotransformer starting
c. wye-delta starting
d. part-winding starting
d. part-winding starting
Which of the following may be eliminated as a concern in good motor maintenance?
a. Number of hours and days the motor operates
b. Manufacturer of the motor
c. Environmental conditions
d. Importance of the motor in the production scheme
b. Manufacturer of the motor
Determine proper electrical connections before electrical connection of a motor by ____.
a. checking with a rotation tachometer
b. using a rotation and phase tester
c. using a recording meter
d. observing the rotation of the motor
b. using a rotation and phase tester
Which of the following is usually an indication of a bad motor bearing?
a. Hot bearing housing
b. Low current draw
c. Low pull-in torque
d. Sparking at the brushes
a. Hot bearing housing
When using compressed air to clean motors, which of the following precautions should be taken?
a. Make sure the air is warmer than the ambient motor temperature.
b. Use air pressure within safety standards.
c. Avoid using a pulse nozzle.
d. Use only a high-velocity nozzle.
b. Use air pressure within safety standards.
A type of motor bearing with a very low rate of failure is a ____.
a. radial bearing
b. pin bearing
c. sealed bearing
d. ballbearing
c. sealed bearing
The polarization index is the ratio of the resistance after ten minutes to the resistance after ____.
a. 60 minutes
b. 30 minutes
c. 5 minutes
d. 1 minute
d. 1 minute
Which of the following statements is true con- cerning motors in storage?
a. Shafts should not be moved or turned until the motor is put in use.
b. Shafts should be turned according to manufacturer instructions.
c. Shafts should be turned 180 degrees once a year to distribute bearing grease.
d. Shafts should be turned once every three years to keep them from rusting.
b. Shafts should be turned according to manufacturer instructions.
The best attachment point for lifting motors is/are the ___.
a. eyebolt
b. shaft
c. base
d. end bells
eyebolt
What is a Megger?
A trade term for Megohmeter. A meter used to check the insulation resistance of the windings for insulation deterioration.
