Motors Book - Chapter 6

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Motors Book Quizzes & Trivia

Questions and Answers
  • 1. 

    A(n) ___ motor is an induction motor with the squirrel-cage conductor bars replaced with coils of wire, and with added slip rings, brushes, and a resistor  circuit.

    • A.

      Design

    • B.

      Induction

    • C.

      Wound-rotor

    • D.

      Electronic

    Correct Answer
    C. Wound-rotor
    Explanation
    A wound-rotor motor is an induction motor with the squirrel-cage conductor bars replaced with coils of wire, and with added slip rings, brushes, and a resistor circuit. This type of motor allows for variable speed control and improved starting torque, making it suitable for applications that require adjustable speed and high starting torque. The slip rings and brushes provide electrical connections to the rotor windings, allowing external resistors to be added to the circuit, which helps control the motor's speed and torque characteristics.

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  • 2. 

    A wound-rotor motor can be distinguished from a squirrel-cage induction motor by the presence of the ___.

    • A.

      Coils of wire in the winding slots instead of the solid conductor bars

    • B.

      Three slip rings on the shaft

    • C.

      External resistance bank

    • D.

      All of the above

    Correct Answer
    D. All of the above
    Explanation
    A wound-rotor motor can be distinguished from a squirrel-cage induction motor by the presence of coils of wire in the winding slots instead of the solid conductor bars. Additionally, a wound-rotor motor has three slip rings on the shaft, which are used to connect external resistance to the rotor circuit. Therefore, the correct answer is "all of the above" as all three options differentiate a wound-rotor motor from a squirrel-cage induction motor.

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  • 3. 

    A(n) ___ ring is a metallic ring mounted on a motor shaft and electrically insulated from the shaft.

    • A.

      Slip

    • B.

      Conducting

    • C.

      Shorting

    • D.

      Induction

    Correct Answer
    A. Slip
    Explanation
    A slip ring is a metallic ring mounted on a motor shaft and electrically insulated from the shaft. Slip rings are used in electrical machines to transmit power and electrical signals from a stationary part to a rotating part. They allow for continuous electrical connection between the stationary and rotating parts, even when the rotation causes the wires to twist. Slip rings are commonly used in applications such as generators, motors, and wind turbines.

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  • 4. 

    A ___ is an extended, flexible connection or a braided copper conductor.

    • A.

      Coil winding

    • B.

      Pigtial

    • C.

      Eutectic alloy

    • D.

      Plug fuse

    Correct Answer
    B. Pigtial
    Explanation
    A pigtial is an extended, flexible connection or a braided copper conductor. It is commonly used in electrical and electronic applications to provide a secure and reliable connection between components. The braided copper conductor allows for flexibility and durability, making it ideal for applications where movement or vibration is present. Pigtails are often used in wiring harnesses, grounding systems, and as connectors for various devices.

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  • 5. 

    The ___ carries the entire rotor current.

    • A.

      Slip ring

    • B.

      External resistor circuit

    • C.

      Brush rigging

    • D.

      Melting-alloy overload relay

    Correct Answer
    B. External resistor circuit
    Explanation
    The external resistor circuit is responsible for carrying the entire rotor current. In an electric motor, the rotor current is the current flowing through the rotor windings, which is necessary for the motor to operate. The external resistor circuit is connected to the rotor windings and helps control the speed and torque of the motor. By adjusting the resistance in the circuit, the amount of current flowing through the rotor can be regulated, allowing for precise control of the motor's performance.

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  • 6. 

    The maximum ___ is produced when the maximum resistance is connected to the rotor and the induced frequency is at its highest.

    • A.

      Flux

    • B.

      Current

    • C.

      Torque

    • D.

      None of the above

    Correct Answer
    C. Torque
    Explanation
    When the maximum resistance is connected to the rotor and the induced frequency is at its highest, it means that there is a greater opposition to the flow of current in the rotor. This increased resistance results in a stronger magnetic field and greater torque production. Torque is the rotational force that causes an object to rotate, so when there is a higher torque, there is a greater tendency for the object to rotate. Therefore, the maximum torque is produced in this scenario.

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  • 7. 

    A wound-rotor motor ___ is a device containing high-wattage resistors that is designed to control the speed of a wound-rotor motor and operate in variable-speed mode for as long as needed.

    • A.

      Regulator

    • B.

      Starter

    • C.

      Resistor

    • D.

      Drum switch

    Correct Answer
    A. Regulator
    Explanation
    A wound-rotor motor regulator is a device that contains high-wattage resistors, allowing it to control the speed of a wound-rotor motor. This regulator operates in variable-speed mode, meaning it can adjust the motor's speed as needed. It is designed to be used for as long as necessary, providing a reliable and adjustable power source for the motor.

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  • 8. 

    A ___ is a type of regulator.

    • A.

      Drum switch

    • B.

      Three-pole rheostat

    • C.

      Silicon-controlled rectifier

    • D.

      All of the above

    Correct Answer
    D. All of the above
    Explanation
    The correct answer is "all of the above" because all three options mentioned - drum switch, three-pole rheostat, and silicon-controlled rectifier - are types of regulators.

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  • 9. 

    A ___ is switch with tapped resistors used to switch a set of resistors in or out of a wound-rotor circuit. 

    • A.

      Drum switch

    • B.

      Silicon-controlled rectifier

    • C.

      Three-pole rheostat

    • D.

      Wound-rotor motor starter

    Correct Answer
    C. Three-pole rheostat
    Explanation
    A three-pole rheostat is a switch with tapped resistors used to switch a set of resistors in or out of a wound-rotor circuit. It allows for variable resistance and control over the speed and torque of a wound-rotor motor. This type of switch is commonly used in industrial applications where precise control over motor performance is required.

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  • 10. 

    A rheostat uses a three-___ to start the wound-rotor motor.

    • A.

      Wire enclosure

    • B.

      Wire control circuit

    • C.

      Pole rheostat

    • D.

      Pole circuit

    Correct Answer
    B. Wire control circuit
    Explanation
    A rheostat is a type of variable resistor that is used to control the flow of electric current in a circuit. In the context of starting a wound-rotor motor, a wire control circuit would be used with a rheostat. This circuit would allow for the adjustment of the resistance in the circuit, which in turn would control the starting current and speed of the motor. By using a wire control circuit with a rheostat, the motor can be started smoothly and gradually, preventing any sudden surges in current that could damage the motor.

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  • 11. 

    Resistors designed for starting are able to dissipate the ___ generated during the short time required for starting the motor.

    • A.

      Heat

    • B.

      Current

    • C.

      Voltage

    • D.

      Magnetism

    Correct Answer
    A. Heat
    Explanation
    Resistors designed for starting motors are able to dissipate the heat generated during the short time required for starting the motor. When a motor starts, there is an initial surge of current flowing through the resistors, which causes them to heat up. These resistors are specifically designed to handle this temporary increase in heat and prevent any damage to the motor or other components. By dissipating the heat efficiently, these resistors ensure a smooth and safe start for the motor.

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  • 12. 

    Increasing the resistance of the rotor while it is ___ reduces the current in the rotor windings and reduces the speed of the motor.

    • A.

      Starting

    • B.

      Stopping

    • C.

      Running

    • D.

      None of the above

    Correct Answer
    C. Running
    Explanation
    Increasing the resistance of the rotor while it is running reduces the current in the rotor windings and reduces the speed of the motor. This is because increasing the resistance in the rotor circuit limits the flow of current, which in turn reduces the torque produced by the motor. As a result, the motor slows down and its speed decreases.

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  • Mar 21, 2023
    Quiz Edited by
    ProProfs Editorial Team
  • Dec 18, 2012
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    Tacowallace
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