Question 1

In an automatic speed control for a two-speed, two-winding three-phase motor, the circuit is so designed that a certain amount of speed must be achieved before the motor can be changed from low to high speed.

Accepted Answer

False

Question 2

The use of an automatic starter and a control station gives greater operating efficiency.

Accepted Answer

An automatic starter controls the starting and stopping of a motor, while a control station allows for remote operation and monitoring of the motor. Together, they can improve operating efficiency by automating the process and reducing the need for manual intervention. An automatic starter allows for easy and quick starting of a motor, while a control station allows for remote operation and monitoring of the motor, both of which increase operating efficiency.

Question 3

The phrase pairs of poles is used to indicate that poles are always in pairs.&#10;A)reduction&#10;B)motor&#10;C)squirrel&#10;D)cage

Accepted Answer

Magnetic poles, as found in motors, always come in pairs; for every north pole, there is a corresponding south pole.

Question 4

Using the formula for speed, the speed of a two-pole motor supplied by 60-hertz electrical energy is determined.&#10;A)factory-preset&#10;B)discrete&#10;C)rated&#10;D)synchronous

Accepted Answer

The speed of a two-pole motor supplied with 60-hertz electrical energy is synchronous, meaning it rotates at a speed that is directly proportional to the frequency of the AC power source. The synchronous speed of a two-pole motor supplied with 60-hertz electrical energy is 3600 revolutions per minute (RPM). Therefore, the correct choice is D (synchronous). The synchronous speed of a motor is determined by the frequency of the electrical energy supplied to it. In the case of a two-pole motor supplied with 60-hertz energy, the synchronous speed can be calculated using the formula Synchronous Speed (in RPM) = 120 x Frequency (in Hz) / Number of Poles. Therefore, the correct answer is D) synchronous.

Question 5

Slow and continued speed transfers may activate the overload relays.

Accepted Answer

Overload relays are designed to protect motors and circuits from excessive current draw due to overloads, not from slow or continued speed transfers. They are triggered by current exceeding a preset level for a certain period, not by the speed of operation.

Question 6

The squirrel cage induction motor is a .&#10;A)constant-speed motor&#10;B)reduced-speed motor&#10;C)variable-speed motor&#10;D)high-speed motor

Accepted Answer

The squirrel cage induction motor is a constant-speed motor because its speed is determined by the frequency of the power supply and the number of poles in the motor. It is not designed for variable speed control without additional equipment. The squirrel cage induction motor is a constant-speed motor, meaning that its speed is determined by the frequency of the power supply and the number of poles in the motor's construction. It is not designed to be adjustable or have variable speeds.

Question 7

The squirrel cage induction motor is the most widely used industrial motor.

Accepted Answer

The squirrel cage induction motor is commonly used in various industrial applications due to its efficiency and ruggedness. The squirrel cage induction motor is the most commonly used industrial motor due to its lower cost, simpler design, and low maintenance requirements.

Question 8

The inactive winding must be open circuited to circulating current due to transformer action between the idle winding and the energized winding.&#10;A)reduce&#10;B)prevent&#10;C)monitor&#10;D)promote

Accepted Answer

Open circuiting the inactive winding prevents circulating current due to transformer action between the idle winding and the energized winding, which can cause overheating and damage to the transformer. Open circuiting the inactive winding helps to prevent circulating current due to transformer action between the idle and energized winding, as the circuit is broken and the current cannot flow through the inactive winding.

Question 9

The design of the motor will determine the percentage of slip.

Accepted Answer

The design of the motor, including the size and number of rotor bars, affects the amount of slip that occurs in the motor. The design of the motor, including the number of poles and the type of rotor winding, will determine the percentage of slip in an asynchronous motor.

Question 10

The operating principle on which the squirrel cage motor is based calls for a rotor .&#10;A)turning in the stator direction&#10;B)in protection mode&#10;C)revolving within a stator&#10;D)operating at high speeds

Accepted Answer

The squirrel cage motor is based on the principle of a rotor revolving within a stator. The stator provides a magnetic field that induces a current in the rotor, which in turn creates its own magnetic field and causes the rotor to spin. The rotor does not turn in the stator direction, but instead revolves within it. The motor does not operate in protection mode, nor does it require high speeds for its operation. The squirrel cage motor operates with a rotor that revolves within a stator. The stator generates a rotating magnetic field, which induces a current in the conductors of the rotor. This current produces a magnetic field, which interacts with the magnetic field from the stator and causes the rotor to turn. Therefore, the correct choice is C - "revolving within a stator".

Deck 31: Controllers for Two-Speed Two-Winding 28separate Winding29 Motors