Line Y-1 Flashcards
What is the given name to the stationary part of the motor?
Stator
What is the given name to the rotating part of the motor?
Rotor
What is the purpose of the laminations in the cores of the rotor and stator?
To reduce Eddy currents
Why are the bars of the squirrel cage slightly skewed so that they are not parallel with the slots in the stator?
To make the motor run smoothly
What is the main purpose of the end bells on a motor?
To house the bearings that support the rotor shaft and to keep it aligned with the stator
What two ways are motor enclosures classified?
The way they protect the motor from the environment
The way they are cooled
What name is given to the machine with an enclosure that does not prevent the free exchange of air between the inside and the outside of the machine?
Open machine
What name is given to the machine with an enclosure that prevents the free exchange of air between the inside and the outside of the machine?
Totally enclosed machine
The windings of a three-phase winding is made up of three single-phase windings placed _________ electrical degrees apart from each other
120
What are the two purposes of the stator core?
Support the stator windings
Provide a low-reluctance path for the magnetic circuit
What does the frame designation tell about the motor?
The physical dimensions of the motor in NEMA standards
Does the horsepower rating of the motor refer to input power or to output power?
Output power, at rated speed
What does the service factor of the motor tell about the motor?
The service factor, when multiplied by the horsepower rating of the motor, gives the maximum power by the motor may be required to supply continuously without damaging the motor
What would an electrician use the insulation system designation for when installing a motor?
To determine the insulation (temperature) type of the supply conductors
What does the ambient temperature rating refer to?
The highest temperature allowed for the cooling medium that contacts the heated parts of the motor
What units is the speed of the motor rated?
Revolutions per minute (RPM)
For a motor to operate successfully under running conditions at full load, by what maximum percentage may the frequency of the supply vary?
It should not vary more than 5% of the rating on the nameplate
For a motor to operate successfully under running conditions at full load, what is the maximum variation from rated voltage allowed?
It should not vary more than 10% of the rating on the nameplate
What relationship is expressed by the design letter on a motor nameplate?
The relationship between motor torque and motor speed
Define the term “full-load current”
The full-load current is what the motor will draw when it operates at rated voltage and supplies rated horsepower
The flux created by any winding will be at a maximum when the current through that winding is at a __________
Maximum
When the current through a winding reverses, the flux direction created by that winding __________
Reverses
What effect does increasing the frequency of the supply have on the speed of the rotating magnetic field?
Increasing the frequency of the supply increases the speed of the rotating magnetic field.
What effect does increasing the number of poles have on the speed of the rotating magnetic field?
Increasing the number of poles in the machine decreases the speed of the rotating magnetic field