Introduction to Three-Phase Induction Motors 030302a Flashcards
What is an Electric Motor?
A device that Converts Electrical power (energy) into Mechanical power (energy)
What is an Induction Motor?
Is a machine that gets energy into the rotating part by Mutual Induction.
This transfer of energy uses “transformer action”
What is another name for Torque?
“The Moment of Force”
What basic tool is used to measure Torque?
A “Prony Brake”
What is the Formula used to calculate Torque?
T = F • r
F - Force
r - Radius
What sophisticated tool do we use to measure Torque?
A Dynamometer
What is Torque measured in?
Newton-Metres (Nm)
What is Force measured in?
Newtons (N)
When referring to the radius in a Torque calculation; which unit do we measure the radius in?
Meters (m)
What 3 things make up the formula for Mechanical Power(P)?
- Rotational Speed (Frequency)
- Torque
- A numeric constant (9.55)
What formula would you start with to calculate the Torque Output of a 10kW motor?
P=(T•n)/9.55
What formula would you start with to calculate the Torque Output of a 10hp motor?
hp=(T•n)/(9.55•746W)
What is the formula for Efficiency?
P.out(Mech)
Divided by
P.in(elect)
The categories of losses in an induction motor are _________ and __________.
Electrical & Mechanical
Name the 2 types of ELECTRICAL losses in an induction motor.
Iron losses (Core losses) and Copper losses
What are Iron Losses (Core Losses)?
Losses that occur in the stator and the rotor.
Which part of a motor do we see Copper losses?
Copper losses occur in the stator and the rotor.
Name the 2 types of Mechanical losses.
Friction and Windage
Describe Friction and Windage as they pertain to Mechanical losses.
Friction is the energy loss from creating heat which occurs in the bearings and between brushes and slip rings when they are used.
Windage is the energy lost due to the air movement produced by the rotor.
What method is used during rotor construction to prevent “cogging”?
Skewing or Slanting of the rotor bars
Name two types of rotors used in induction motors.
- Squirrel-cage Rotors
- Wound Rotors
What are the two major components of a stator?
- Stator Core
- Stator Winding
What is Windage?
It’s a Mechanical loss of energy due to the air movement produced by the rotor.
The Counter-torque produced by a dynamometer or prony brake is the product of what two (2) mechanical quantities?
- Force
- Radius (to the point where the torque is measured)