Induction Motors and DC Machines Quiz

DC machines operate based on Faraday's Law. This law states that an electromotive force (EMF) is induced in a conductor when it cuts through a magnetic field, causing current to flow if the circuit is closed.

The relative speed between the rotor and stator of an induction motor. Expressed as a percentage, it indicates the difference between synchronous speed and rotor speed.

The speed at which the magnetic field rotates in an induction motor. It is determined by the frequency of the supply and the number of poles in the motor.

The speed of the rotor in an induction motor.

The winding that carries the DC current and creates the magnetic field in a DC machine.

The winding that rotates in a DC machine, generating the EMF or experiencing a torque.

The magnetic field in an inductor opposes changes in current flow. The induced EMF always acts in a direction to oppose the change in flux that caused it.

A series DC motor has its field winding connected in series with the armature winding. A shunt DC motor has its field winding connected in parallel with the armature winding.

The speed at which the magnetic field rotates in a synchronous motor or generator.

The difference between the synchronous speed (Ns) and the actual rotor speed (Nr) of an induction motor, expressed as a percentage of Ns.

The actual speed at which the rotor of an induction motor rotates.

The number of poles in an electric motor or generator determines the synchronous speed for a given frequency.

The relationship between the number of poles (P), frequency (f), and synchronous speed (Ns). It's the formula used to calculate Ns: Ns = (120 * f) / P.

The power developed within the armature of a DC generator, before losses are accounted for.

The resistance of the armature winding in a DC generator or motor.

The resistance of the shunt field winding in a DC shunt generator or motor.

The total voltage generated by the DC machine armature, accounting for the voltage drops across the armature resistance and the series field resistance.

The voltage applied to the load in a DC generator. It is also known as terminal voltage.

The current flowing through the armature winding of a DC machine.

The resistance of the series field winding, connected in series with the armature in a series generator.

The total current delivered by a DC generator to the load.

The current flowing through the shunt field winding of a DC machine. It creates the main magnetic field.

A type of rotor used in induction motors, characterized by a cylinder with bars embedded in slots, short-circuited by end rings. Think of it like a squirrel cage spinning within the magnetic field.

A type of rotor used in induction motors, featuring windings connected to slip rings for external resistance adjustment. This allows for speed control and increased starting torque.

The relative difference between synchronous speed and rotor speed in an induction motor, expressed as a percentage. Higher slip means slower rotor speed compared to the magnetic field.

The maximum torque an induction motor can produce at a specific slip value. Occurs when the rotor resistance is equal to the reactance.

The torque required to sustain normal operation under full load conditions. It corresponds to the operating point on the torque-slip curve.

The torque generated by the motor when it first starts. Varies based on the motor design and load.

The relationship between torque and slip for an induction motor, illustrated by a curve. It helps understand how torque changes with changing rotor speed.

A region on the torque-slip curve where the motor operates at a low slip value. Torque increases linearly in this region.

A type of induction motor where the starting winding has higher resistance than the main winding, creating a phase difference between their currents. This phase difference creates a rotating magnetic field, leading to the motor's starting torque.

A type of induction motor that uses a capacitor connected in series with the auxiliary winding, providing a larger phase shift between the main and auxiliary winding currents. This increased phase difference results in a stronger starting torque.

The difference in phase between the currents in the main winding and the auxiliary winding of a single-phase induction motor. A larger phase angle leads to a stronger starting torque.

The winding in a single-phase induction motor that provides the main current path. It is typically inductive in nature, meaning it resists changes in current.

The additional winding in a single-phase induction motor, connected in parallel with the main winding. It helps provide the starting torque during the initial phases.

A mechanical switch that disconnects the auxiliary winding of the motor when it reaches a certain speed, typically 75% to 80% of synchronous speed. This is to reduce power loss and improve efficiency.

The speed at which the magnetic field rotates in a single-phase induction motor. It is determined by the frequency of the supply and the number of poles in the motor.

The difference between the synchronous speed of the magnetic field and the actual speed of the rotor in a single-phase induction motor. It is used as a measure of the motor's efficiency.

A type of AC motor where a capacitor is connected in series with an auxiliary winding, providing high starting torque, used in devices like washing machines, fans, and oil burners.

Similar to a capacitor start motor, but the capacitor remains connected permanently for improved power factor and efficiency. Used in appliances like refrigerators and air conditioners.

A motor where each stator pole is divided into two parts, one shaded with a copper band. This shading creates a rotating magnetic field, allowing the motor to start without a separate starting winding.

A type of induction motor with a rotor similar to the stator winding, allowing external resistance to be added. It is used for applications requiring adjustable speeds and torque control.

A type of induction motor with a rotor resembling a squirrel cage, offering simple construction and low maintenance. Requires external resistance for speed control.

These motors are typically used for smaller appliances like fans and tools, taking advantage of their robust and simple design.

These motors are used for a range of home appliances with higher power requirements, such as washing machines, refrigerators, and air conditioners.

These motors are excellent for applications requiring adjustable speeds and control, such as machine tools and industrial processes.