DC Motors
What is the function of a commutator in an electric motor?
To reverse the direction of the current.
Which type of motor does not require a separate power source for the rotor?
Induction motor
What is the primary principle behind an electric motor?
Electromagnetic induction
Motors are rated in _________
Horsepower (HP)
How is torque calculated in electric motors?
(9.55 x power)/Speed in rpm
Which type of motor uses brushes and a commutator?
DC motor
What is the primary function of the stator in an electric motor?
To generate a rotating magnetic field
What is the function of the stator?
To produce a magnetic field
The frequency of the rotor current in an induction motor is equal to __________
Slip x Input frequency
How do you calculate motor efficiency?
(Output power/Input power) x 100
What is the purpose of the laminations in the core of an electric motor?
To provide electrical insulation
Which type of motor is commonly used in household appliances like refrigerators and air conditioners?
Single-phase induction motor
What is the function of the rotor?
It interacts with the magnetic field to generate torque
In an electric motor, the __________ acts as a contact between the commutator and the battery
Carbon brushes
Which two leads are generally swapped to change the direction of rotation?
T1 and T3
What determines the speed of a DC motor?
Back EMF
What is the role of a centrifugal switch in a single-phase induction motor?
To disconnect the starting winding
What is a split-phase motor?
A single-phase AC motor with a main winding and a starting winding
What causes the rotor to move in an electric motor?
Changes in polarity in the stator
What is insulation resistance testing?
Measure the resistance between the motor windings and ground with a megger
Which type of motor provides the highest starting torque?
DC series motor
Which motor type is commonly used in HVAC systems?
Induction motor
What happens if an AC motor operates above its rated ambient temperature?
It could cause accelerated breakdown of the winding insulation
How do you calculate synchronous speed?
(120 x f)/#of poles
What is the difference between Torque and Power?
Torque is the rotational force
Power is the rate of doing work