Transformers
Transformers are rated with this abbreviation
VA
1hp= ? watts
746watts
what size motor, in horsepower, is required to produce approximately 30 kw of output?
40hp
For most practical purposes, Transformer efficiency should be what?
Ignored
What is FLA rating?
The amperes that the motor draws while carrying its rated horsepower load at it's rated voltage.
what is the approximate output of a 15 hp motor?
11 kW
This effect can be reduced by dividing the core into many flat sections or laminations
Eddy currents
A motor has two opposing magnetic fields in order to rotate. The stationary part is mounted to the stator and the moving part is know as what?
The armature
what is the approximate output of a 5 hp, 480V, three-phase motor?
3.75
Voltage induced in the secondary winding of a transformer is dependent on the number of secondary turns as compared to what?
Primary turns
Once a motor begins turning, how is a counter electromotive force crated?
The rotor-bars are increasingly cut by the stationary magnetic field which created a electromotive force.
the actual motor current depends upon the load on the motor and the operating voltage at the motor terminals.
True or False
True
As current flows through the transformer, the iron core is temporarily magnetized. the energy required to re align the core molecules to the changing electromagnetic field is call "___" loss
Hysteresis loss
In an AC induction motor, a rotating magnetic field is produced by what?
The stator.
The motor FLA rating is used when sizing motor conductors or circuit protection.
True or False
True
The transformer winding that is connected to the source is called the " ____"
Turn ratio
What is the formula to find the FLA of a single phase motor?
FLA= (Motor Hp x 746w)/(E x Eff x PF)
to reverse the rotation of a dc motor, you must reverse the ____.
Stator or Rotor field
Auto transformers use What for the primary and secondary windings?
separate windings
What is the formula to find the FLA of a three phase motor?
FLA=(Motor hp x 746w)/(E x {square root of 3} x Eff x PF)
Dc motors use brushes with springs to hold them in contact with a (an)_____.
commutator