EEE - Battery Exam

Generator

are electrical components that convert mechanical energy into electrical energy by electromagnetic induction.

DC Generator/dynamo

it is an electrical generator that create direct current, converts the alternating current to a direct current, using a commutator; it allows the current flow in one direction only.

AC Generator/alternator

it is an electrical generator that convert mechanical energy to electrical energy in the form of alternating current. In an alternator, the electrical current periodically reverses its direction.

Electrical materials

are basically the parts or elements used in the making of any electrical construction project, developed and constructed for certain purposes

Conductors

is an object or type of material that permits the flow of electric charges from one particle to another.

Insulators

are materials that impede the free flow of electrons. The particles of the insulator do not permit the free flow of electric charges.

Semiconductors

are materials that exhibit electrical behavior somewhere between that of conductors and that of insulators.

• silicon and germanium

Superconductors

It a material that acts strangely when cooled down to a certain temperature. When these materials are at that one special temperature, which we call the critical temperature, they suddenly become perfect conductors, means that their resistance is zero.

Active Components

are nothing but the components that supply and control energy.

Passive components

can be defined as the components that respond to the flow of electrical energy and can dissipate or store energy.

Resistor

is an electrical component that restricts the flow of current in the circuit.

Capacitor

a two-terminal linear passive component that is made from two conductive plates with an insulator between them. It stores electrical energy when an electric charge is forced onto its terminals from a power source. It maintains the charge even after getting disconnected from the power source.

Inductor

or coil or a reactor is a two-terminal passive electrical component and it stores electrical energy in the form of magnetic energy.

Dielectric strength

If the applied voltage exceeds that threshold voltage, there will be a rush of current. It is the voltage required to cause dielectric breakdown, that is, to force current through an insulating material.

ampacity

A conductor’s current-carrying limit is known as its

Insulators

are materials that impede the free flow of electrons. The particles of the insulator do not permit the free flow of electric charges.

Heike Onnes

discovered superconductivity in mercury (Hg) in 1911, for which he won a Nobel prize.

77 K or -195.15 Celsius

High temperature superconductors are compounds exhibiting superconductivity above the liquid nitrogen boiling point of

absolute zero or 10 K (or between -273 Celsius and -263 Celsius)

The critical temperature is usually between

Transistor

is an electronic device, which consists of three terminals, made of semiconductor material that controls the flow of voltage or current and acts as a switch for electronic signals.

Switch

is an electrical device that is used to break the circuit, interrupting the current and to supply the current from one conductor to another conductor. The switch works with the "on" and "off" mechanisms.

Diode/Light-Emitting Diode (LED)

is a device, which is made from a semiconductor material that allows current to flow in one direction; it blocks the current which tries to go against the flow in a wire.

Fuse

is a material or a piece of wire which is used to protect the components from destruction due to the excessive current flowing through them.

Electric wire/cable

are used to connect two or more devices, enabling the transfer of electrical signals or power from one device to the other.

Transformer

A passive electrical device, consists of two coils of wire linked by an iron core or also known as transformer core, that transfers electrical energy between two or more circuits.

Battery

is an electrical device that is used to convert chemical energy into electrical energy through electrochemical discharge reactions.

Absolute Instruments

These are instruments that give the value of quantity to be measured in terms of the physical constants of the instruments and their deflection only, not measurable on a graduated scale.

Secondary Instruments

These are instruments that are calibrated and directly give the value of quantity to be measured.

Indicating Instruments

These are instruments that are fitted with a pointer which moves over a calibrated scale and indicates the electric quantity to be measure directly on the scale.

Recording Instruments

These are instruments that record the electrical quantity to be measure on a graph paper for a desired period. The moving system of the instrument carries an inked pen which rests gently over the graph and moves at a low and uniform speed in a direction perpendicular to that of the movement of the pen.

Integrating instrument

These are instruments that measure the total quantity of electricity consumed in a circuit in a given time.

Motor

An electrical machine that converts electrical energy into mechanical energy.

ammeter, voltmeter, wattmeter

magnetic effect

ammeter, voltmeter, wattmeter

electrodynamic effect

ac ammeter, voltmeter, wattmeter, integrating meter

Electromagnetic induction effect

voltmeter

Electrostatic effect

DC ampere-hour meter

chemical effect

ammeter, voltmeter

heating effect

ammeter

measures electric current

accuracy of the meter

is the ratio of the current when the meter is in the circuit, measured current (IW), to the current without the meter, true current (IO),

percent of loading error

is the percent error in the ammeter reading due to the loading effects that result from the added resistance of the meter

voltmeter

used to measure the potential difference or voltage of a circuit.

multiplier

A simple dc voltmeter can be constructed by placing a resistor (RS) called a ________, in series with the ammeter meter movement, and by marking the meter face to read voltage (V) across the resistor and voltmeter.

Ohmmeter

an instrument to determine resistance. It consists of a battery, a meter movement calibrated to read ohms, and a resistor,

Ro

shown as an adjustable resistor for zeroing and for correcting the aging of the battery.

Rx

is the unknown resistance to be measured

Thevenin’s Theorem

is a method used to change a complex circuit into a simple equivalent circuit.

Thevenin’s Theorem

states that any linear network of voltage sources and resistances, if viewed from any two points in the network, can be replaced by an equivalent resistance, RTH, in series with an equivalent source, VTH.

loading effect

When a voltmeter is connected to a circuit, the voltmeter draws current from the circuit. This current produces a voltage drop across the resistance of the coil, which is subtracted from the voltage being measured. This reduction in voltage is called the _________.

multimeter

is a single instrument capable of measuring voltage, resistance, and current. The volt-ohm-milliammeter (VOM) is the most common multimeter.

dc voltmeter

A typical VOM has a meter movement with a full-scale current of 50 µA or a sensitivity of 20 kΩ/V when used as a __________.

Ac meters

measure electrical quantities of current and voltage that change in amplitude and direction periodically with time.

Half Wave Rectifier Circuit

• simplest type of ac voltmeter

• the diode permits current to flow in one direction during the positive half-cycle and presents a very high resistance to current in the other direction during the negative half-cycle. The resulting current through the meter results is a rms calibrated reading.

Full Wave Rectifier Circuit.

One way of improving the sensitivity of a rectifier type of ac meter is to use

electrocution

The voltage of the electricity and the available electrical current in regular businesses and homes has enough power to cause death by

Static Electricity

is accumulation of charge on surfaces as a result of contact and friction with another surface. This contact/friction causes an accumulation of electrons on one surface, and a deficiency of electrons on the other surface.

Dynamic Electricity

is the uniform motion of electrons through a conductor (this is known as electric current).

wattmeter

• is an instrument that measures dc power or real ac power

• uses fixed coils to indicate current in the circuit, while the movable coil indicates voltage.

• rated in terms of its maximum current, voltage, and power.

yoke/field frame

• outer frame of a dc generator is called

• is made up of cast iron or steel

• provides mechanical strength to the whole assembly and also carries the magnetic flux produced by the field winding.

Field winding/field coil

is an electromagnet that produces the flux cut by the armature. It is made up of many turns of wire that are securely fastened over the iron core of the pole shoes.

Field Poles

are joined to the yoke with the help of bolts or welding.

armature core

is considered as the rotor of a generator, it is mounted on a shaft that rotates in bearings located in the generator's end frames. It acts as a conductor when it is rotated in the magnetic field and it is laminated to reduce the eddy current losses.

an armature coil with a single turn of wire

A simple dc generator consists of

pole/pole shoe/field pole.

The magnetizing force inside a generator is produced by an electromagnet consisting of a wire coil called as field winding/field coil, and a core called

armature assembly

consists of the armature core, armature coils/armature windings, commutator, and other associated mechanical parts.

armature coil/armature winding

is a former wound copper coil which rests in armature slots.

commutator

is used to convert the alternating current flowing in its armature into the direct current at its terminals. It is located at one end of the armature and consists of wedge-shaped segments of hard-drawn copper with one pair of segments for each armature coil.

Brushes

ride on the surface of the commutator and act as the electrical contact between armature coils and an external circuit. A flexible braided-copper conductor, called a pig-tail, connects each brush to the external circuit.

Separately excited

The generator's field coils are energized or excited from an independent external dc source, such as a battery.

Self-excited

When a generator supplies its own excitation; field coils are energized from the current produced by the generator itself.

Series-wound

Where the field winding in series with armature winding.

Shunt-wound

Where the field winding in parallel with armature winding.

Compound-wound

Combination of series and shunt winding. It is used more extensively than other types of generators because it can be designed so that it has a wide variety of characteristics.

Short-shunt

When the shunt field is in parallel only with the armature

Long-shunt

When the shunt field is in parallel with both the armature and series field.

generator, motor

The function of a ________ is to generate a voltage when conductors are moved through a field, while that of a ______ is to develop a turning effort, or torque, to produce mechanical rotation.

stator

Used to carry the field winding and poles. It is a hollow cylinder and together with the rotor constitutes the magnetic circuit or core of the machine.

Rotor

Used to carry the armature winding. It is cylindrical in shape. The armature is the load carrying member.

Armature winding

Used as load carrying member mounted on the rotor. This winding rotates in the magnetic field set up at the stationary winding (Field winding).

Field Winding

An exciting system which may be an electrical winding or a permanent magnet and which is located on the stator.

Commutator

Rotates with the rotor and serves to rectify the induced voltage and the current in the armature, both of which are alternating current.

Brushes

Conducting carbon graphite spring loaded to ride on the commutator and act as interface between the external circuit and the armature winding.

Poles

Provided to place field winding. The number of poles is determined by the voltage and current ratings of the machine.

Sloth/Teeth

A magnetic material used for mechanical support, protection from abrasion, and further electrical insulation. Also, it is used to avoid non-conducting slot liners are wedged between the coils and the slot walls

Motor Housing

Provided to supports the iron core, the brushes and the bearings.

Torque

is the starting twist or force that produces rotation in a motor. This rotation is necessary to get motors started.

Full-load torque

.Necessary to produce its rated horsepower (hp) at full-load speed.

Pull-up torque

Required to bring motor up to rated speed.

Breakdown Torque

Maximum torque the motor will develop with rated voltage applied at rated frequency without an abrupt drop in speed.

Locked-rotor torque

Developed when full power is applied when rotor is stationary; the starting torque or twist that gets the rotor running.

Shunt motor

This is the most common type of dc motor. It is connected in the same way as the shunt generator. Its characteristic speed-load and torque-load curves show that the torque increases linearly with an increase in armature current, while the speed drops slightly as the armature current is increased.

Speed

is designated by the number of revolutions of the shaft with respect to time and is expressed in units of revolutions per minute (rpm).

reduction

A __________of the field flux of a motor causes the motor speed to increase.

• Both motor and supply lines are protected from flow of excessive current

• Motor-starting torque should be made as large as possible

two requirements for motors

stator and rotor

Another way of classifying an alternator is by its

Revolving-armature type alternator

It is similar in construction to the DC generator, in that the armature rotates within a stationary magnetic field. This type of setup is typically found only in alternators with a low power rating and generally is not used.

Revolving-field type alternator

It has a stationary armature winding (stator) and a rotating-field winding (rotor). The advantage of this configuration is that the armature is connected directly to the load without sliding contacts in the load circuit.

DC Alternator

It has the same function as DC generators. They produce alternating current that is then converted to direct current before it enters an aircraft's electrical system. However, the difference is that, in an alternator the magnetic poles rotate and induce voltage into a fixed, or stationary winding.

AC Alternator

Capable of producing a great deal of power and, therefore, typically found on larger aircraft and military aircraft. Furthermore, since alternating current can be carried through smaller conductors, AC alternators allow appreciable weight savings

single phase alternator

the stator is made up of several windings connected in series to form a single circuit.