acdc

Question 1

are widely used for the purpose of converting energy from one form to another.

Answer 1

Rotating electrical machines

Question 2

Source-to-work conversion machine.
Engine is an example of

Answer 2

Prime movers

Question 3

Converts electrical energy into mechanical energy.

Answer 3

Motor

Question 4

Converts mechanical energy into electrical energy.

Answer 4

Generator

Question 5

A type of electrical machine which acts as a mechanical rectifier, inverter or frequency converter.

Answer 5

Rotary Converter

Question 6

Michael Faraday first found it in the 1830s.

Answer 6

Electromagnetic Induction

Question 7

the induced voltage in a coil is proportional to the product of the number of loops and rate at which the magnetic field changes within the loops

Answer 7

Faradays Law

Question 8

measures how much magnetic field passes through a given area:

Answer 8

Magnetic flux (Φ_𝐵)

Question 9

formula for Magnetic flux (Φ_𝐵)

Answer 9

ΦB​=B⋅A⋅cosθ
𝐵= magnetic field strength (Tesla, T)
𝐴= area of the surface (m²)
𝜃= angle between the magnetic field and the surface normal

Question 10

States that an induced electric current flows in a direction such that the current opposes the change that induced it.

e= - N dØ / dt

Answer 10

Lenz’s law

Question 11

Where:
Force in dynes
Flux Density in lines per sq. cm (maxwell/sq.cm or Gauss)
Current of conductor in ampere
Length of conductor in cm

Answer 11

F = (B * I * L) / 10

Question 12

where:
T – torque, N-m
F - force, Newton
r - armature radius, meter

Answer 12

T = ( F x r)

Question 13

Electrical energy to mechanical energy
uses electricity

Answer 13

DC MOTORS

Question 14

Mechanical energy to electrical energy
produces electricity

Answer 14

DC GENERATORS

Question 15

refers to the electrically rotating component of a dc motor and generator. It is responsible for the armature winding and the load-bearing part is the armature

Answer 15

ROTOR

Question 16

refers to the electrical static or fixed parts of a dc motor and generator. Stators are made up of three parts: a yoke or frame, field windings, and poles. When a voltage is provided to the rotor, the stator does not move and instead creates a magnetic field around it, causing the rotor to rotate

Answer 16

STATOR

Question 17

Deliver electrical energy from the supply circuit to the rotor. Brushes serve as an interface between the external circuit and the armature winding. They are often constructed of carbon or graphite.

Answer 17

BRUSHES

Question 18

Its primary function is to supply electric current to the armature windings. The generated north pole from the armature will be attracted to the field winding’s south pole and vice versa. It also rectifies the induced voltage and current in the armature.

Answer 18

COMMUTATOR

Question 19

Used to energize the rotor’s static magnetic field. This winding revolves inside the magnetic field created by the stationary winding. It is wrapped around the armature core’s slot. It may be produced using two methods: lap winding and wave winding.

Answer 19

ARMATUREWINDING

Question 20

is utilized to sustain the stator’s static magnetic field. It is a system that is situated on the stator and can be an electrical winding or a permanent magnet.

Answer 20

Field winding

Question 21

has a small cross-sectional area and serves just to keep the pole shoe over the yoke,

Answer 21

pole core

Question 22

which has a greater cross-sectional area, spreads the flux produced throughout the air gap between the stator and rotor to decrease reluctance loss. The pole shoe also has slots for the field windings

Answer 22

Pole shoe

Question 23

serves as a protective cover for both the rotor and the stator. It serves as the generator’s covering, supporting the armature and housing the magnetic poles, field windings, and the pole to create magnetic fields for the rotor.

Answer 23

YOKE / FRAME

Question 24

reverses the polarity to achieve the constant direction of current.

Answer 24

Split Ring or Commutator

Question 25

At the gap on the split rings, the voltage is zero and once it touches again the ring,

Answer 25

the current flows continues

Question 25

Increasing the Rotational Speed of the Coil increases the ?

Answer 25

Amount of EMF

Question 26

is used to refer to any rotary electrical machine that converts direct current electrical energy into mechanical energy.

Answer 26

DC motor

Question 27

PERMANENT MAGNET DC GENERATORS formula

Answer 27

To calculate the induced voltage, we use the formula 𝑽_𝒊𝒏𝒅=𝑩𝒍𝒗 Where: Vind = induced voltage measured in volts B = flux density the is perpendicular to the motion l = length of the conductor v = velocity of the conductor measured in m/s

Question 28

SEPARATELY EXCITED DC GENERATORS formula

Answer 28

To find the value of the voltage and the power generated we use the formula: 𝑽=𝑰𝑹_𝒂 And; 𝑷_𝒈= 𝑬_𝒈×𝑰 To find the power delivered to the external load we use: 𝑷_𝑳=𝑽×𝑰 Where: Ia = Armature current IL = Load current V = Terminal voltage Eg = Generated EMF

Question 29

SERIES WOUND GENERATOR

Answer 29

The formula for the voltage is: 𝑽=𝑬_𝒈− 𝑰^ × 𝑹_𝒂 And the generated power is computed by: 𝑷_𝒈=𝑰 × 𝑬_𝒈 𝑷_𝒍=𝑰 ×𝑽

Question 30

SHUNT WOUND GENERATOR

Answer 30

The armature current (Ia) is composed of two parts which are the shunt field current (Ish) and load current (Il). This is denoted as: 𝑰_𝒂= 𝑰_𝒔𝒉+ 𝑰_𝒍 ----- 𝑰_𝒔𝒉= 𝑽/𝑹_𝒔𝒉 𝑽= 𝑬_𝒈− 𝑰_𝒂 𝑹_𝒂 The generated power in this type of generator can be computed by: 𝑷_𝒈= 𝑬_𝒈 × 𝑰_𝒈 𝑷_𝒍=𝑽 × 𝑰_𝒍

Question 31

LONG SHUNT COMPOUND WOUND GENERATOR

Answer 31

The formula for the shunt field current is: 𝑰_𝒔𝒉= 𝑽/𝑹_𝒔𝒉 The armature current is equal to the series field current shown as: 𝑰_𝒔𝒄= 𝑰_𝑳+ 𝑰_𝒔𝒉 The voltage across the load can be computed by: 𝑽= 𝑬_𝒈−𝑰_𝒂 𝑹_𝒂− 𝑰_𝒔𝒄 𝑹_𝒔𝒄 𝒐𝒓 𝑽= 𝑬_𝒈− 𝑰_𝒂(Ra+Rsc) Lastly, the power generated (Pg) and the power delivered to the load (PL) is computed by: 𝑷_𝒈= 𝑬_𝒈 × 𝑰_𝒂 𝑷_𝑳=𝑽 × 𝑰_𝑳

Question 32

SHORT SHUNT COMPOUND WOUND GENERATOR

Answer 32

The currents in this generator can be computed by: 𝑰_𝒔𝒄= 𝑰_𝑳 𝑰_𝒔𝒉= (𝑽+ 𝑰_𝒔𝒄 𝑹_𝒔𝒄)/𝑹_𝒔𝒉 𝑰_𝒂= 𝑰_𝒔𝒄+ 𝑰_𝒔𝒉 The load voltage, load power, and generated power can be computed with the formula: 𝑽=𝑬_𝒈− 𝑰_𝒂 𝑹_𝒂−𝑰_𝒔𝒄 𝑹_𝒔𝒄 𝑷_𝒍=𝑰_𝒈 × 𝑽 𝑷_𝒈= 𝑰_𝒈 × 𝑬_𝒈

Question 33

is a motor that uses the electromagnetic induction phenomena to convert alternating current into mechanical power. An alternating current is used to power this motor. AC motors are made up of two major components: the stator and the rotor. The stator is the motor's stationary component, while the rotor is the motor's revolving component

Answer 33

AC motor

Question 33

keeps dust and liquids out of an AC motor's internal parts, provides convective cooling, and maintains electrical safety. The level of protection provided is mostly determined by the quality of the materials used to construct the enclosure.

Answer 33

ENCLOSURE

Question 34

The copper wire that is wound around the stator in its slots is referred to as stator windings. The number of slots in the stator is determined by the power phases delivered to the coils. A three-phase motor has six slots and three pairs of 120o offset coil windings. The term "winding" refers to a complete electromagnetic circuit made up of many

Answer 34

STATOR WINDINGS

Question 35

is the space between the rotor and the stator, and it is an important aspect of the motor's construction. Due to tolerances in their size, loose bearings, and movement, the gap must be broad enough to prevent contact between the surfaces of the rotor and stator. To improve the motor's efficiency, the air gap must be as small as possible, as bigger air gaps require more power to produce adequate magnetization.

Answer 35

air gap

Question 36

on an AC motor support and position the rotor, maintain a small air gap, and transfer loads to the motor. They can work at a wide range of speeds while minimizing friction.

Answer 36

BEARING

Question 37

The opposite end of the axle that drives the machine that the AC motor is coupled to has a fan attached to the shaft of the rotor. Cool air is drawn in by the fan and forced across the windings. The enclosure's rear is blown with hot air

Answer 37

FAN

Question 38

The portion of an AC generator that produces voltage is known as the

Answer 38

ARMATURE

Question 39

is made up of conductor coils that receive electricity from the source and generate magnetic flux. The armature is cut by the magnetic flux in the field, which produces a voltage. This voltage is the AC generator's output voltage.

Answer 39

field

Question 40

is the component that drives the AC generator.

Answer 40

PRIME MOVER

Question 41

are electrical connectors that transport electricity from and to an AC generator's rotor. They are primarily used to transfer current from a fixed device to a revolving one.

Answer 41

RINGS WITH A SLIP

Question 42

revolves with a constant (synchronous) speed, as the name implies. The wound rotor in this type of motor receives the excitation (magnetizing) current from its excitation system (a separate direct current source with controller). In comparison to induction motors, synchronous motors are more expensive and require more maintenance. The induction current is not required for the synchronous motor to function. Unlike induction motors, these motors use multiphase AC electromagnets on the stator, which generate a spinning magnetic field.

Answer 42

Synchronous motor