Three phase motor speed
An induction motor with 4 poles, connected to a 50 Hz supply will have a synchronous speed of ?
1500 RPM
A 4 pole motor connected to a 60 Hz supply, will have a synchronous speed of ?
1800 RPM
A 2 pole induction motor connected to a 50 Hz supply will have a Synchronous speed of ?
3000 RPM
When the number of motor poles of an induction motor increases the synchronous speed of the motor will ( increase / decrease )
Decrease
if the supply voltage to a motor is decreased the torque developed between the magnetic fields of the stator and rotor will ( decrease / increase )
Decrease
When the torque developed by an induction motor falls below that which is required to drive a load at the synchronous speed of the motor, there will be an increase in the ____________ speed and a decrease in the ____________ speed ?
INCREASE in the SLIP speed and a DECREASE in the ROTOR speed
When the frequency of the AC supply connected to an induction motor increases the synchronous speed of the motor will be caused to ( increase / decrease )
Increase
The actual speed of the rotor of an induction motor will always be ____________ than the synchronous speed of the motor ?
Less
The term synchronous speed, when related to an induction motor, describes the speed at which the ____________ ____________ of the _____________ rotates?
Magnetic field of the stator rotates
The formula used to calculate the Synchronous speed of an induction motor is ?
Nsync = 120 x f / p
The term Nr refers to the _____________ ______________ of an induction motor ?
Rotor speed
The Slip speed of an induction motor can be found by subtracting the ____________ ____________ from the _____________ _____________ ?
Rotor speed from the Synchronous speed Nslip = Nsync - Nrotor
The term Nslip Refers to the ____________ ____________ of an induction motor ?
Slip speed
Two factors that effect the synchronous speed of an induction motor are?
Supply frequency and the number of motor poles
The term Ns refers to the ______________ ______________ of an induction motor ?
Synchronous speed
The term Nsynch refers to the ?
Synchronous speed
The slip speed of an induction motor is the difference in speed between the ________________ speed and the _________________ speed ?
Synchronous speed and the Rotor speed
A motor designed to have it's speed controlled using windings connected in series. Can have it's speed changed by connecting or disconnecting an extra length of motor winding conductor for each of the existing poles of a motor winding. No extra poles are created. The resistance of each of the motor windings is increased, therefore reducing the current flow through the winding, reducing the power generated and the speed that the motor is able to drive against a given load. The rotor speed decreases as the slip speed increases. ( TRUE / FALSE )
TRUE
a motor that is designed to have it's speed controlled by the pole changing method. Will have two or more sets of motor poles installed about the stator, for each motor winding. the speed of the motor can be changed by connecting or disconnecting these poles. ( TRUE / FALSE )
TRUE
When when a VSD is used to control induction motor speed, the voltage supplied to the motor is altered when the frequency is altered, to ensure the _____________ to ______________ ratio remains constant. This ensures that the torque and power developed by the motor remain suitable to drive the load, and the effects of increased or decreased impedance in the circuit, due to the change in frequency are minimised.
VOLTS to FREQUENCY ratio
