AC Electrical Machines: Three-Phase Induction Motor

<p>To provide a path for the rotor current (A)</p> Signup and view all the answers

<p>To reduce the magnetic losses (B)</p> Signup and view all the answers

<p>$Ns = (120 f/P)$ (B)</p> Signup and view all the answers

<p>Rotor resistance (A)</p> Signup and view all the answers

<p>To create a torque that drives the rotor (B)</p> Signup and view all the answers

<p>The rotor rotates in the same direction as the rotating magnetic field (B)</p> Signup and view all the answers

<p>Due to the relative motion between the rotating magnetic field and the rotor conductors (C)</p> Signup and view all the answers

<p>Rotor currents oppose the change in magnetic flux caused by the rotating magnetic field (D)</p> Signup and view all the answers

<p>To ensure that the rotor currents flow in the direction necessary to create torque (B)</p> Signup and view all the answers

<p>A synchronous motor has a DC field winding on the rotor (D)</p> Signup and view all the answers

<p>fr = sf (C)</p> Signup and view all the answers

<p>f Hz (C)</p> Signup and view all the answers

<p>s = (Ns - N) / Ns (A)</p> Signup and view all the answers

<p>1500 rpm (B)</p> Signup and view all the answers

<p>850 rpm (C)</p> Signup and view all the answers

<p>0.05 (D)</p> Signup and view all the answers

<p>They are very efficient and have a good power factor. (B)</p> Signup and view all the answers

<p>To reduce the slip and the frequency of the rotor current (A)</p> Signup and view all the answers

<p>To generate a magnetic field that interacts with the stator field. (B)</p> Signup and view all the answers

<p>It decreases proportionally to the decrease in slip (B)</p> Signup and view all the answers

<p>To improve the motor's efficiency by reducing iron losses. (D)</p> Signup and view all the answers

<p>The squirrel-cage winding is permanently short-circuited while the wound rotor winding can be connected to external resistors. (D)</p> Signup and view all the answers

<p>Three-phase induction motors are cheaper to build and maintain. (B)</p> Signup and view all the answers

<p>High maintenance requirements. (A)</p> Signup and view all the answers

<p>To allow for the rotor to rotate freely. (C)</p> Signup and view all the answers

<p>To provide a path for current flow between the rotor bars. (D)</p> Signup and view all the answers

An electric motor widely used in industries, operating at constant speed under load.

The stationary part of a three-phase induction motor, housing the stator winding.

The rotating part of the induction motor that carries the rotor winding.

The small distance between the stator and rotor, typically from 0.4 mm to 4 mm.

A type of rotor with parallel slots filled with conductive bars connected at both ends.

A rotor type that uses windings instead of bars and requires external connections.

They include simple construction, low cost, minimal maintenance, high efficiency, and self-starting torque.

Notable cons include constant speed operation and lower starting torque compared to DC motors.

A type of induction motor with a cylindrical core and 3-phase rotor winding.

The speed at which the rotating magnetic field in a motor revolves.

Configuration where rotor windings are connected in a star formation.

The initial torque provided to start an induction motor.

Electrical contacts that allow current transfer to the rotor's windings.

The rotor runs in the same direction as the stator field to reduce speed difference.

The difference between synchronous speed and rotor speed, expressed as a percentage.

At standstill, the rotor current frequency matches the supply frequency; changes with slip when rotor moves.

When the rotor is stationary, slip equals 1, and rotor frequency is equal to the supply frequency.

When the rotor runs faster, the slip decreases and the rotor current frequency changes accordingly.

Slip can be calculated using the formula: s = (Ns - N) / Ns, where N is rotor speed.

Frequency of rotor current when rotor speed is at a specific value; it’s calculated using fr = sf.

The total magnetic flux resulting from summing individual flux components.

A magnetic field that rotates around the stator at synchronous speed.

Electromotive force generated in the rotor due to the rotating field.

The rotational force produced by current-carrying rotor conductors.

A law stating that induced currents oppose the change that created them.

The rotor that remains still while the magnetic field rotates.

The force acting on the rotor due to the interaction with the stator's magnetic field.