1B Flashcards
An ___ ___ ___ is a network of electrical components used to supply, transmit, and use electric power.
electrical power system
Oftentimes, there is a need for redundant sources of power, as there could be a drop or total loss of the primary source of energy. What offer an effective solution to these problems?
Batteries, automatic switching devices, and uninterruptible power
supplies (UPS) offer an effective solution to these problems.
____ convert chemical energy into electrical energy, specifically DC.
Batteries
Figure 1-94 shows the symbols for a battery. In both symbols, the shorter lines represent the ____ terminal, and the longer lines represent the ____ terminal.
negative
positive
A multi-cell battery consists of two or more cells in ____ (connected end-to-end). For example, a flashlight might have two (2) or three (3) “D” cell batteries connected end-to-end, where the negative terminal of one cell connects to the positive terminal of the next cell.
series
Batteries are divided in two cell categories:
Primary
Secondary
Several factors impact a battery’s life span:
the battery’s age, the temperature of the environment in which the battery is operating, the charge times, and the amount of use.
What are some examples of primary cell batteries?
Carbon zinc and alkaline are primary cells
Primary cell batteries are also called a ___ ___ because of its
moist paste electrolyte.
dry cell
___ ___ are not designed for recharging and must be discarded
following their end-of-life.
Primary cells
Carbon zinc, known as the ___ ___, was invented by Georges Leclanché in 1866.
Leclanché Cell
Despite being considered the oldest type of battery, it is still commonly used today.
Carbon Zinc
However, the carbon zinc battery has been mostly replaced by ___ ___, which will be discussed later on.
alkaline batteries
The shelf-life of carbon zinc cells degrades over time, but their shelf life can be extended by storing them at temperatures in the ___° F range.
40 degree
Carbon Zinc cells come in a variety of shapes, sizes, but all deliver a nominal voltage of 1.5V per cell. A few examples of sizes include…?
D, C, AA, AAA and 9V.
Where high current drain is required, the ___ ___ is the best choice. ___ ___ easily handle the current drain that would strain the capacity of other types of batteries.
alkaline battery
Like the carbon zinc cells discussed earlier, alkaline cells cover the entire range of all commonly used cell types like:
D, C, AA, AAA and 9V
Alkaline cells also offer a nominal output voltage of ___V per cell.
1.5V
Alkaline cells cost three times as much as carbon-zinc cells, but
despite the increase in cost, alkaline batteries account for __% of manufactured batteries in the US today.
80%
It is possible that over time the cell may ____, causing a leakage of the internal chemicals. Alkaline cells contain a very corrosive electrolyte that will destroy sensitive equipment.
rupture
A ___ ___ or ___ is one that can be recharged and reused.
secondary cell or battery
Lead-acid, nickel cadmium, and lithium are common types of ___ ___.
secondary cells
What are the two types of secondary cells?
Lead acid and lithium-ion
Recharging a cell to its original pre-discharge condition is accomplished by passing current through the circuit in the
___ ___ to the current during discharge.
opposite direction
The ___-___ ___, invented in 1859, is the oldest type of rechargeable cell.
lead-acid cell
The ___ ___ is probably the best-known application of the lead-acid cell.
car battery
Its ratio of charging power to discharge power is a big advantage.
lead-acid
The lead-acid battery cannot be sealed, as the recharge cycle generates gases that must be ___.
vented
A lead-acid cell’s nominal voltage is ___V per cell.
2.0V
nominal voltage is about ___V per cell, but it can vary from about 2.7V (discharged) to about 4.23V (fully charged).
3.0V
The lithium-ion battery is lightweight, has a high power capacity, suffers no memory effect, and has a long shelf-life. Because of its low maintenance features, the lithium-ion battery is considered
an ___ ___ when the need for a rechargeable (secondary) battery arises.
optimal choice
Generators convert ___ energy into ___ energy.
mechanical
electrical
AC generators, also known as ___, are generally capable of producing a pure sine wave output voltage of constant
frequency.
alternators
___ ___ are standalone machines that provide electricity when power from the local grid is unavailable.
electrical generators
As with batteries, the requirements of the application
will drive decisions about the ___ and ___ ___ of the
generator that is needed.
size and fuel type
Generators also provide power in two different ways: ___ ___ and ___ ___ While the type of power they provide is the same, the way that they do so varies.
single phase and three phase
Single-phase generators produce one single voltage (120V or 120/240V) that alternates ___.
continuously
Because the power for single-phase generators is generated in ___ ___ ___, the level varies throughout its cycle. These varying waves cause the power level to drop throughout the process. These drops generally go undetected to the eye and ear in normal, residential, and smaller operations. However, sensitive electronic equipment, such as heavy-duty electric motors and large data centers, can be negatively impacted by the power drops of single-phase power.
one single wave
___ ___ ___ work by producing three separate waves of AC power that operate in a sequence.
Three-phase generators
Three-phase generators has continuous flow of energy. The power level ___ ___ as it does with single-phase generators. Because of this uninterrupted reliability, three- phase generators are much more powerful.
never dips
___ ___ are often used to supply backup power to facilities, businesses, or homes during power outages. These are typically three-phase generators, producing 120/208V or 277/480V of usable power.
Industrial generators
Traditionally, ___ ___ (CE) is responsible for installing and maintaining equipment such as generators.
Civil Engineering
Alternators have three major assemblies:
the stator, the rotor, and the brush.
A sometimes-confusing issue when discussing alternators is the term “armature.” In all motors and DC generators, the terms “___” and “___” are synonymous.
rotor
armature
With alternators, “armature” always refers to the ___ supplying the output voltage.
coils
Since an alternator’s output may be taken from either the rotor or stator coils, the term armature may…?
apply to either
The stator assembly has three component items:
the frame, the pole pieces, and the coils.
What does the frame in the stator assembly do?
The frame supports the pole pieces and the coils.
What do the pole pieces do in the stator assembly?
The pole pieces are made of laminated, soft steel segments around which the coils are wound.
What do the coils do in the stator assembly?
The coils are made of several turns of insulated wire wrapped
around each of the pole pieces which forms the stator.
The rotor assembly consists of four component items:
the shaft, the core, the coils, and the slip rings.
The rotating axle on which the rotor core and coils are mounted is called the ___.
shaft
The brush assembly consists of:
a brush, a spring, and a holder for each slip ring
____ are small blocks of carbon-graphite which provide a
current path to the rotating slip ring.
Brushes
___ push the brushes firmly against the slip rings to maintain good electrical contact.
Springs
Basic alternator theory consists of three main factors:
They are all required to mechanically generate electricity.
a conductor, a magnetic field, and relative motion.
A ___ ___ must supply the relative motion by turning the rotor inside the stationary stator.
prime mover
A ___ ___ must supply the relative motion by turning the rotor inside the stationary stator. The armature coils provide the conductor. Permanent magnets or electromagnets provide the magnetic field. Most alternators use a battery or rectified AC to provide current to the field windings to create the magnetic field.
prime mover
The field windings will be either the ___ or ___ coils, depending on where the output voltage is taken.
stator or rotor
There are two types of alternators:
rotating armature and rotating field
An ATS (Figure 104) is an integral part of the power generation process. It allows for smooth and immediate transfer of electrical current between multiple sources and the load (e.g., end-user equipment), while maintaining ____ between the sources (e.g., utility power and generator power).
isolation
The primary purpose of an ____ ____ ____ system is to provide an alternate source of clean AC power in an emergency.
Uninterruptible Power Supply (UPS)
UPSs come in a variety of topologies, depending on the
level of protection needed. In general, and as seen in
Figure 105, the basic UPS is a combination of a…?
battery, a charger and an inverter
___ ___ (Figure 1-107) are comprised of many of the components previously mentioned in this objective. For example, generators provide a source of current and voltage (power) to the power supply. The transformer contains inductors. The rectifier has diodes and resistors. The filter has capacitors and inductors. The voltage regulators contain resistors, diodes, and other components.
Power Supplies
The pulsating DC, as seen in Figure 1-108, is either positive or negative and is constantly changing in amplitude. The pulsating DC is applied to the ____ section and is converted into a smoother DC.
filter
Half-wave rectifiers aren’t very efficient. This is because one half of the cycle of the AC input is ___ by the diode. As a result, output voltage is zero half of the time. This causes inconsistency in the voltage level and can be detrimental to electronic equipment. This also causes the output frequency to be the same as the input frequency. For every one Hertz (or cycle per second), there
will be only one output pulse per second. Even though the half-wave only passes one alternation of the AC sine wave, it still produces an output voltage that is equal to the input voltage (peak) from the transformer’s secondary (Vs).
blocked
As seen in Figure 1-110, a full-wave bridge rectifier uses ___ diodes
instead of one. The diodes are arranged in a diamond pattern on the diagram for illustration purposes only.
four
The easiest way to understand this is by determining which side of the diode is closest to the ___ ___ ___. Figure 1-111A shows a half-wave rectifier where the anode of the diode is closest to the transformer’s secondary. The anode is the positive material of the diode, so current will flow during the positive alternation, and the rectifier will generate a positive DC output signal. In Figure 1-111B, the diode is reversed. Now, the cathode is closest to the transformer’s secondary. Current will flow during the negative alteration, and the rectifier will generate a negative DC output signal. On the full-wave bridge rectifier, all diodes must be reversed to change the output of the DC signal’s polarity.
transformer’s secondary coil
Notice in Figure 1-112 the capacitor is placed directly on the output of the ___ ___r. A capacitor has the useful characteristic of resisting changes in voltage. It accomplishes this by building up a charge across its plates when the input voltage increases. Then, when the input voltage starts to decrease, the voltage across the capacitor will not decrease as fast. The capacitor will start discharging its energy down through the grounds that are connected, up through RL to the top half of the capacitor. In other words, instead of the voltage going up and down in rhythm with the AC signal, like it does in the rectifier, the capacitor makes up the difference, keeping the voltage more constant across RL, as shown at the bottom of the figure.
bridge rectifier
The difference between the minimum DC voltage and the maximum DC voltage in the filtering stage is called the ___ ___ (Figure 1-113).
ripple amplitude
The bigger the capacitor, the more energy it stores, and the lower the resulting ripple amplitude. The lower the ripple amplitude, the smoother the filtered waveform, and the closer the output will be to a ___ ___ ___.
flat DC voltage
The Shunt voltage regulator, also called a Zener diode voltage regulator, has the Zener diode in parallel, or shunt, to the load device. Figure 1-116 shows the Zener diode (D1) is in parallel with
the load device and in series with the current-limiting resistor (R1). Note also that the normal current flow through a Zener diode is with the ___. The reverse bias voltage of D1 regulates the output voltage on the load. The entire operation of the shunt regulator is in response to changes in voltage or current.
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