Chapter 9 Flashcards

1
Q

AHJ

A

Authority Having Jurisdiction
The building official, electrical
inspector, fire marshal, or other
individuals or entities
responsible for interpretation
and enforcement of local
building and electrical codes.
TDMM.* Page G-14

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2
Q

Alternating Current
(ac)

A

A current flow that alternates
periodically (usually sinusoidal)
in magnitude and direction.
TDMM.* Page G-7

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3
Q

Apparent Power

A

The product of the measured
voltage and measured
amperage. Expressed in
volt amperes.
TDMM.* Page 9-10

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4
Q

Arc Flash

A

A short circuit through the air.
When insulation or isolation
between electrified conductors
is breached or can no longer
withstand the applied voltage, an
arc flash occurs.
TDMM.* Page 9-28

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5
Q

AWG

A

American Wire Gauge
A system used to specify wire
size. The greater the wire
diameter, the smaller
the AWG value.
TDMM.* Page G-8

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6
Q

Capacitance

A

1 . The ability of an electronic
component to store electrical
energy.
2. The opposition to a change in
voltage.
TDMM.* Page G-30

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7
Q

Delta

A

The difference between two
values, symbolized with a
triangle (△).
TDMM: Page G-54

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8
Q

Direct Current (dc)

A

Current flow that has a constant
direction. The letters dc are also
used generically to refer to any
constant waveform or signal
(e.g., a battery voltage of 3 volts
direct current [Vdc]).
TDMM: Page G-58

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9
Q

Frequency

A

The number of cycles that a
periodic signal completes in a
given time. If the unit of time is
one second, the frequency is
stated in hertz (Hz). One Hz is
equal to one cycle per second.
TDMM.* Page G-83

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10
Q

Harmonics

A

Multiples of the basic frequency
of a sine wave (e.g., the third
harmonic of 60 Hz power
frequency is 180 Hz).
TDMM.* Page 9-79

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11
Q

Impedance

A

The total opposition to ac
current flow. Measured in ohms.
TDMM.* Page 9-8

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12
Q

Inductance

A

1 . The property of an electrical
force field built around a
conductor when current flows
through it.
2. The resistance to change in
current.
TDMM: Page G-95

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13
Q

ITE Power

A

Information Technology
Equipment Power
The power consumed by ICT to
manage, monitor, control,
process, store, and route data
within the data center, excluding
all infrastructure technology
equipment.
TDMM.* Page G-96

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14
Q

LOTO

A

Lockout/ Tagout
A means to protect personnel
from the unexpected start-up or
reenergization of equipment by
ensuring that equipment
remains completely shut off
during routine maintenance
and repairs.
TDMM.* Page 9-29

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15
Q

LVD

A

Low Voltage Disconnect
A device that is used to
disconnect the battery at a
preset voltage during battery
discharge and allow
reconnection only when utility
power has been restored. Called
a “no volt release” in the
United Kingdom.
TDMM.* Page 9-54

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16
Q

Noise

A

Unwanted electrical signals that
are induced onto, or superimposed
upon, the power line.
TDMM.* Page 9-79

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17
Q

PDU

A

A device that has a transformer,
surge suppression, single-point
ground, panelboards, and
monitoring under a single
enclosure.
TDMM.* Page 9-26

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18
Q

Phase Difference

A

The relationship in time
between two waveforms
of the same frequency.
TDMM.* Page 9-3

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19
Q

Phase Configuration

A

The number of phases and the
type of connection between the
utility and the user.
TDMM.* Phase 9-4

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20
Q

Power

A

1 . The rate of transfer or
absorption of energy per unit time
in a system.
2. The energy required to operate
an electrical device (e.g., motor,
amplifier, telephone transmitter).
TDMM.* Page G-146

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21
Q

Reactance

A

The opposition to the flow of ac
current caused by inductance
and capacitance. Expressed
in ohms.
TDMM.* Page 9-8

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22
Q

Redundancy

A

Providing secondary
components that either become
instantly operational or are
continuously operational so that
the failure of a primary
component will not result in
mission failure.
TDMM.* G-761

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23
Q

Resistance

A

A measure of opposition a
material offers to the flow of
direct current. Measured
in ohms.
TDMM.* Page G-765

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24
Q

RPP

A

Remote Power Panel
A power distribution cabinet
downstream from a power
distribution unit (PDU) or
uninterruptible power supply
(UPS), typically containing
circuits and breakers, without a
transformer, located
near the load.
TDMM.* Page G-763

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25
SDS
Safety Data Sheet A document prepared by the manufacturer describing all known chemical, radiological, and other hazards of a specific product. Formerly called material safety data sheet (MSDS). TDMM.* Page G-168
26
Short Circuit
A faulty or accidental connection between two points of different potential in an electric circuit, bypassing the load and establishing a path of low resistance through which an excessive current can flow. TDMM.* Page 9-13
27
Sine Wave
The mathematical representation of an alternating voltage or current waveform. TDMM.* Page 9-2
28
SPD
Surge Protection Device A protective device for limiting transient voltages by diverting or limiting surge current. It has a nonlinear voltage-current characteristic that reduces voltages exceeding the normal safe system levels by a rapid increase in conducted current. Also called a voltage limiter, overvoltage protector, (surge) arrestor, or transient voltage surge suppressor (TVSS). TDMM.* Page G-189
29
STS
Static Transfer Switch A device that can transfer electrical loads between two synchronized power sources in a break before making (open transition) transfer in a fraction of a second, typically one quarter of a cycle. TDMM.* Page 9-50
30
UPS
Uninterruptible Power Supply A system that provides a continuous supply of power to a load using stored energy when the normal source of energy is not available or is of unacceptable quality. A UPS will provide power until the stored energy of the system has been depleted, or when the acceptable quality of either an alternative source of power (e.g., generator) or the normal source of power returns to acceptable quality. TDMM.* Page G-202
31
Wye
A power system in which only one point (usually the midpoint of a supply transformer bank) is grounded. If the neutral is present, it is not grounded along the line. TDMM.* Page G-211
32
What is an ac circuit?
An electrical current that periodically reverses (alternates) its direction of flow because the polarity of the voltage source constantly changes TDMM.* Page 9-2
33
What term is used to describe the mathematical representation of an alternating voltage or current waveform?
Sine wave TDMM: Page 9-2
34
What is a sine wave cycle?
One variation of the sine wave from zero to maximum (positive), back through zero, to minimum (negative), and back to zero TDMM.* Page 9-2
35
What term is used to describe the number of times a sine wave cycle occurs in one second?
Frequency TDMM.* Page 9-2
36
What unit of measure is used to express the frequency of a sine wave cycle?
Hertz (Hz) TDMM.* Page 9-2
37
How is the rms value of a sine wave calculated?
By multiplying the zero-to-peak value of the sine wave by 0.7071 TDMM.* Page 9-2
38
Name 4 defined characteristics of ac power provided by commercial utility sources.
1 .Frequency (in Hz) 2.Voltage (in V) 3.Power (in kVA or kW) 4.Phase (single or three-phase) TDMM.* Page 9-2
39
Name 2 typical frequencies provided by commercial utility sources.
1.50 Hz 2.60 Hz TDMM.* Page 9-3
40
What is the most common single-phase service voltage value?
120/240 v TDMM.* Page 9-3
41
What are the most common three-phase service voltage values?
*208 Y/120 V *240 v *480 Y/277 V TDMM.* Page 9-3
42
What is the available power of a given system?
The amperage that is available to the user at the nominal system voltage TDMM.* Page 9-3
43
What units of measure are used to express the available power for a large system?
*Kilovolt-ampere (kVA) *Kilowatt (kW) TDMM: Page 9-3
44
What does phase difference describe?
The relationship in time between two waveforms of the same frequency TDMM.* Page 9-3
45
What does it mean if two waveforms are described as being "in phase"?
That the two waveforms match each other in electrical degrees TDMM.* Page 9-4
46
How many waveforms are produced when electrical power is generated?
3 waveforms, each 120 degrees out of phase with the others TDMM.* Page 9-4
47
What is phase configuration?
The number of phases and the type of connection between the utility and the user TDMM.* Page 9-4
48
What term is used to describe the electrical system between the serving utility and the customer's site?
Distribution system TDMM.* Page 9-6
49
What is the electrical wiring system?
The cabling between the connection to the distribution system at the customer's site and various equipment (loads) to be powered TDMM.* Page 9-6
50
Name 3 characteristics of various loads that affect the amount of power required for those loads.
1 .Resistance 2.Inductance 3.Capacitance TDMM.* Page 9-7
51
Which characteristics are responsible for creating the difference between the real power (in watts) and the apparent power (in volt- amperes) for the required load of an ac circuit?
Inductance and capacitance TDMM.* Page 9-7
52
True or False The formula for Ohm's law always applies to dc circuits.
True. The formula for Ohm's law always applies to dc circuits, but it only applies to ac circuits that are purely resistive (e.g., incandescent lamps, resistive heating elements). TDMM.* Page 9-8
53
What is reactance?
The opposition to the flow of ac current caused by inductance and capacitance TDMM.* Page 9-8
54
What term is used to describe the total opposition to ac current flow?
Impedance TDMM.* Page 9-8
55
What is inductive reactance?
The portion of impedance that opposes a change in current flow because of magnetic field coupling TDMM.* Page 9-8
56
What is capacitive reactance?
The portion of impedance that opposes a change in voltage because of electric field coupling TDMM.* Page 9-8
57
What formula is used to calculate the power for a purely resistive ac circuit?
P=V x I TDMM.* Page 9-9
58
What determines the lag time in an ac circuit with inductive reactance?
The amount of inductance TDMM.* Page 9-9
59
What is apparent power?
The product of the measured voltage and measured amperage TDMM.* Page 9-70
60
How is apparent power expressed?
In volt-amperes (VA) TDMM.* Page 9-10
61
Where are measurements for apparent power performed?
On the line side of the system TDMM.* Page 9-10
62
Where are measurements for real power performed?
On the load side of the system TDMM.* Page 9-70
63
How is real power expressed?
In watts (W) TDMM.* Page 9-10
64
What is used to show the relationship between watts and volt-amperes?
Power factor (PF) TDMM.* Page 9-10
65
What measurement is commonly used for typical loads if the PF is unknown?
0.8 TDMM.* Page 9-71
66
What type of power is used to size electrical distribution equipment?
Apparent power TDMM.* Page 9-11
67
What unit of measure is used to indicate the amount of power that is consumed by a circuit at any given time?
Watts TDMM.* Page 9-11
68
How are watt-hours determined?
By multiplying the number of watts consumed by the number of hours that the watts are being consumed TDMM.* Page 9-11
69
What unit of measure is used for heat?
British thermal unit (Btu) TDMM.* Page 9-11
70
What is the efficiency of a circuit or load?
The amount of input power required to provide a predetermined output power, expressed as a percentage TDMM.* Page 9-12
71
What does horsepower (HP) measure?
Mechanical power TDMM.* Page 9-72
72
What factors must be known in order to calculate voltage drop?
*R = Resistance per foot of the conductor (ohms/ft) (amperes) *l = Current in the conductor *L = One-way length of circuit (footage) *A = Cross-sectional area of conductor (circular mils) *K = Specific resistance TDMM.* Page 9-12
73
What is a short circuit?
A faulty or accidental connection between two points of different potential in an electric circuit, bypassing the load and establishing a path of low resistance through which an excessive current can flow TDMM.* Page 9-73
74
Why is a short circuit study performed?
To determine the required ratings for the power distribution system equipment TDMM.* Page 9-13
75
What is the purpose of the AWG system?
To provide a standard reference for comparing various conductor materials TDMM.* Page 9-15
76
What has an AWG system number represented historically?
Roughly the number of steps involved in the process of wire drawing TDMM.* Page 9-75
77
What is the relationship between the AWG number and the size of the wire it represents?
It is an inverse relationship. The smaller the number, the larger the wire. TDMM.* Page 9-75
78
What is a circular mil?
A unit of area equal to the area of a circle one mil in diameter TDMM.* Page 9-15
79
What formula is used to convert circular mils to square mils?
Square mils = Circular mils x 0.7854 TDMM.* Page 9-76
80
Name 3 characteristics related to the ampacity of a conductor.
1 .Conductor size 2.Temperature 3.Means of insulation TDMM.* Page 9-17
81
Name 4 forms of distortion that may be present in the power created by the utility.
1 .Voltage fluctuations 2.Current fluctuations 3.Frequency variations 4.Noise TDMM.* Page 9-18
82
Define surge as it relates to voltage and current fluctuation.
Short duration (usually subcycle) rapid increase in voltage or current that can often be up to thousands of volts in amplitude. The duration is less than a half cycle (8.3 milliseconds) of the normal voltage waveform. TDMM.* Page 9-18, Table 9.3
83
Define swell as it relates to voltage and current fluctuation.
An increase in the nominal voltage or current lasting from 0.5 cycles to one minute. TDMM.* Page 9-18, Table 9.3
84
Define sag as it relates to voltage and current fluctuation.
A decrease in nominal voltage or current lasting 0.5 cycles up to one minute. TDMM: Page 9-18, Table 9.3
85
What is overvoltage?
An increase in the nominal voltage for more than 3600 cycles (one minute) TDMM.* Page 9-18, Table 9.3
86
What is undervoltage?
A decrease in the nominal voltage for more than 3600 cycles (one minute) TDMM.* Page 9-18, Table 9.3
87
What term is used to refer to a total absence of voltage on one or more phase conductors for a period of time?
Interruption TDMM.* Page 9-18, Table 9.3
88
True or False Frequency variation is a common occurrence.
False. Frequency variation is not a common occurrence. TDMM.* Page 9-19
89
Name 3 sources of frequency variation.
1 .lnadequately regulated source 2.Utility company correction 3.Switching TDMM.* Page 9-19
90
What are the harmonics of a sine wave?
Multiples of the basic frequency (e.g., the third harmonic of a 60 Hz power frequency is 180 Hz) TDMM.* Page 9-79
91
What is the maximum allowable total harmonic distortion of the voltage waveform per IEEE 519?
5 percent TDMM.* Page 9-79
92
What term is used to describe unwanted electrical signals that are induced onto, or superimposed upon, the power line?
Noise TDMM.* Page 9-19
93
Name 2 categories of noise related to power distribution.
1 .Common-mode noise 2.Differential-mode noise TDMM.* Page 9-19
94
What type of noise is present between phase and ground or between neutral and ground, but not between each line?
Common-mode noise TDMM.* Page 9-79
95
What is differential-mode noise?
Noise that is present between phases or phase and neutral. Also known as normal mode noise. TDMM.* Page 9-19
96
What is an isolated ground (IG)?
An equipment grounding (earthing) topology that was theorized to reduce the effects of electromagnetic interference and radio frequency interference on the equipment grounding (earthing) system TDMM.* Page 9-79
97
Name 2 methods for identifying IG receptacles.
1 .Continuous orange receptacle coloring 2.Beige receptacle marked with an orange triangle upon its face TDMM.* Page 9-19
98
Are IG systems recommended for use with voice and data equipment?
No. IG systems are not recommended for use with voice and data equipment. Though such an equipment grounding (earthing) system is permitted (provided it meets stringent wiring techniques), it defeats the purpose of an equipotential plane that is desired for all EFs, ERs, and TRs. TDMM.* Page 9-19
99
How does electrostatic discharge cause equipment to malfunction?
By inducing noise impulses TDMM.* Page 9-20
100
What level of humidity should be maintained in an ER or TR to prevent electrostatic discharge?
30 to 55 percent TDMM.* Page 9-20
101
What is a potential result of a current imbalance?
High-magnitude neutral currents TDMM.* Page 9-20
102
What is the NEC guideline for sizing feeder and branch circuit conductors?
Feeder and branch circuits should be sized for the noncontinuous load plus 125 percent of the continuous load. TDMM.* Page 9-20
103
What is the guideline for sizing the neutral conductor?
It is advised to size the neutral conductor to carry 200 percent of the rated load, which must be continuous from the outlet all the way back to where the source is derived. TDMM.* Page 9-21
104
What is a drawback associated with installing oversized neutrals?
Increased construction costs TDMM.* Page 9-21
105
What is the purpose of a three-phase K-rated transformer?
To dissipate the heating effects caused by harmonics on the neutral conductor TDMM.* Page 9-21
106
What does the K rating of a transformer denote?
The transformer's ability to safely dissipate the heating effects caused by harmonics on the neutral conductor TDMM.* Page 9-21
107
What type of receptacle is generally recommended for any critical equipment loads?
Locking type TDMM: Page 9-22
108
What is galvanic corrosion?
A breakdown in the electrical connection between the two dissimilar metals TDMM.* Page 9-23
109
What is the maximum distance a listed ITE power cord can extend?
4.5 m (15 ft) TDMM.* Page 9-24
110
What is the purpose of the EPO switch in an ITE space?
To provide a safe electrical shutdown of all electrical equipment in the ITE space, especially in case of fire TDMM.* Page 9-24
111
What is a possible negative impact of an EPO switch in an ITE space?
It could act as a single point of failure for critical ITE. TDMM.* Page 9-24
112
Name 3 ways that power is distributed to equipment.
1 .Panelboards 2.Power distribution units (PDUs) 3.Remote power panels (RPPs) TDMM.* Page 9-25
113
Name 2 main types of OCPDs.
1 .Circuit breakers 2. Fuses TDMM.* Page 9-25
114
What type of device has a transformer, surge suppression, single-point ground, panelboards and monitoring under a single enclosure?
Power distribution unit (PDU) TDMM.* Page 9-26
115
What device can be described as a PDU without a transformer?
Remote power panel (RPP) TDMM.* Page 9-27
116
What term is used to describe a short circuit through the air?
Arc flash TDMM.* Page 9-28
117
What is the maximum temperature of an arc flash?
-19,427ºC (35,000ºF) TDMM.* Page 9-28
118
What is the purpose of having a qualified engineer perform an arc flash hazard analysis?
TO have the engineer provide recommendations for mitigating hazards as well as labels to be installed on equipment TDMM.* Page 9-29
119
What is the purpose of LOTO procedures?
To protect personnel from the unexpected start-up or reenergization of equipment by ensuring equipment remains completely shut off during routine maintenance and repairs TDMM.* Page 9-29
120
What type of device provides a physical means to render an energy source inoperable?
Lockout (LO) device TDMM.* Page 9-29
121
What information is included on a tagout (TO) device?
*Who locked out the equipment *When the equipment was locked out *The reason and duration of the lockout TDMM.* Page 9-29
122
Name 4 benefits of incorporating LOTO procedures into a facility's operation and maintenance plan.
1 .Preventing injuries or fatalities 2.Avoiding unnecessary penalties, fines, or litigation 3.Avoiding shutdowns to critical operations 4.Maximizing uptime, productivity, and profitability TDMM.* Page 9-29
123
Name the 4 basic steps of a LOTO procedure.
1.ldentify the energy source. 2.Isolate the energy source. 3.Lock and tagout the energy source. 4.Prove that the energy source is effectively isolated. TDMM.* Page 9-30
124
What does N represent when defining redundancy requirements?
N = Need TDMM.* Page 9-31
125
What are the common expressions of redundancy?
*N-Base requirement *N+1 redundancy *N+2 redundancy *2N redundancy *2(N+1) redundancy TDMM.* Page 9-31
126
What is the purpose of the Uptime Institute's tier system?
To provide a methodology to evaluate a data center's site infrastructure in relation to a desired operational availability target TDMM.* Page 9-31
127
What is the focus of ANSI/BICSI 002?
The expected performance of systems and the overall site, providing the flexibility to meet a site's specific needs TDMM.* Page 9-31
128
What is the redundancy capacity of a Class 1 electrical system?
There is no redundant capacity. TDMM.* Page 9-32
129
What class is assigned to an electrical system with a single path with redundant components?
Class 2 TDMM.* Page 9-33
130
How many paths are typically active in a Class 3 electrical system?
Only 1 TDMM.* Page 9-33
131
Why are Class 4 electrical systems rare?
The number components that need to be installed to obtain the level of redundancy results in an expensive solution. TDMM.* Page 9-34
132
Name the 3 major categories of power conditioning devices.
1 .Devices that filter and/or regulate the utility supplied power 2.Equipment that regenerates the utility supplied power or generates its own power 3.Static uninterruptible power supply (UPS) units TDMM.* Page 9-36
133
Name 3 alternatives to static UPS units.
1 .Rotary UPS units 2.Flywheel UPS units 3.Modular UPS units TDMM.* Page 9-36
134
True or False An isolation transformer has no electrical connection between the primary and the secondary.
True. An isolation transformer has no electrical connection between the primary and the secondary. TDMM.* Page 9-36
135
When are shielded isolation transformers preferred over standard isolation transformers?
When the total load is made up of more than 20 percent of nonlinear type equipment TDMM.* Page 9-37
136
What is the purpose of a surge protection device (SPD)?
To limit, clamp, or divert surges and transients TDMM.* Page 9-37
137
Where are SPDs installed when the stage approach is used as recommended?
*Service entrance panel as a service protector *Distribution panelboard level *Branch circuit panelboard level TDMM.* Page 9-37
138
What is the purpose of voltage regulators?
To adjust the line voltage to the load up or down, as necessary, providing that the input voltage remains within the range of the regulator TDMM.* Page 9-38
139
What is a power line conditioner?
A unit that incorporates two or more conditioning and protection methods and sometimes has a power distribution means complete with main and branch circuit breakers TDMM.* Page 9-38
140
What is the purpose of a harmonic filter?
To reduce voltage waveform distortion that affects sensitive electronic equipment TDMM.* Page 9-38
141
How do motor generators provide electrical isolation from the utility line?
By using the utility to drive a motor, which in turn drives a generator, producing an ac waveform at the desired voltage TDMM.* Page 9-39
142
What component in the motor generator is used to ride through short outages of up to a few seconds?
A flywheel TDMM.* Page 9-39
143
How are engine generators typically used?
As a standby power source when long-term backup is required TDMM.* Page 9-39
144
Name 4 factors that must be considered when designing an engine generator system.
1. Size of the load 2. Level of redundancy required 3. Cost, space, and environmental constraints 4. Total cost of ownership of the generator system TDMM.* Page 9-39
145
Name 3 typical generator topologies.
1 .Single generator (N) 2.Multiple generators (N+l) 3.Paralleled generators TDMM.* Page 9-39
146
What is the purpose of a static UPS unit?
To protect critical loads from most types of power fluctuations TDMM.* Page 9-40
147
When do off-line UPS units provide backup power?
When the utility power goes below preset tolerances TDMM.* Page 9-40
148
What is a line-interactive UPS unit?
An off-line UPS unit with line conditioning capabilities included TDMM.* Page 9-41
149
How does an online double conversion UPS unit charge a battery?
By completely rectifying the ac line from ac to dc TDMM.* Page 9-41
150
What type of UPS is the most common in ICT design and construction?
Double conversion TDMM.* Page 9-41
151
What is the purpose of a maintenance bypass?
To provide an isolated path around the UPS so that the critical load can continue to be supplied with utility power TDMM.* Page 9-41
152
Name 5 factors that must be considered when designing a UPS system.
1.Critical load calculation 2.Critical load support interval 3.Level of redundancy required 4.Cost, space and environmental constraints of the particular project 5.Total cost of ownership for the UPS and battery system TDMM.* Page 9-42
153
What is the most common multimodule UPS configuration?
Parallel redundant UPS system TDMM.* Page 9-43
154
What is a possible drawback of a parallel redundant UPS system?
The common output bus or common static switch can be seen as a single point of failure. TDMM.* Page 9-44
155
What is a possible drawback of an isolated redundant UPS system?
It is a costly and space- consuming system. TDMM.* Page 9-45
156
What is an advantage of a distributed redundant UPS system?
One distribution path can be taken down, and the critical load will not be affected. TDMM.* Page 9-46
157
Name 2 disadvantages associated with using a ring bus topology for a UPS system.
1. High cost 2. Complexity TDMM.* Page 9-47
158
Name 5 advantages associated with using rotary UPS units.
1. Efficiency 2. Tolerance for short circuit currents 3. Tolerance for input voltage and frequency departures 4. Tolerance for large step load changes 5. Tolerance for high inrush currents TDMM.* Page 9-48
159
Name 3 advantages of using a flywheel UPS unit instead of a static UPS unit.
1 .Lower life cycle cost 2.Less space required 3.Less taxing on engine generators TDMM.* Page 9-49
160
What drawback is associated with modular UPS units?
It contains more components than other topologies, which increases the likelihood of component failure. TDMM.* Page 9-49
161
What type of device can transfer loads between two synchronized power sources in a break before making transfer in a fraction of a second?
Static transfer switch (STS) TDMM.* Page 9-50
162
What is an advantage associated with a point-of-use STS?
There are two power switches all the way up to the critical load, minimizing single points of failure TDMM.* Page 9-57
163
Name 3 factors that determine the amount of protection that an electrical system needs.
1 .Site power distribution design 2.Known existing power problems 3.Potential power problems TDMM.* Page 9-51
164
What is the nominal operating voltage for telecommunications in the United States?
Negative 48 V TDMM.* Page 9-52
165
What is the nominal operating voltage for cellular radio in the United States?
Positive 24 V TDMM.* Page 9-52
166
Where is the voltage usually set for a rectifier/charger?
To the float charge voltage required by the battery TDMM.* Page 9-53
167
What is the central point of the dc power system?
Switchboard TDMM.* Page 9-53
168
Name the 2 types of power board distribution.
1. Centralized 2. Decentralized TDMM.* Page 9-53
169
What piece of equipment is used to change dc power to ac power?
Inverter TDMM.* Page 9-53
170
What is a low voltage disconnect (LVD)?
A device that is used to disconnect the battery at a preset voltage during battery discharge and allow reconnection only when utility power has been restored TDMM.* Page 9-54
171
What is a disadvantage of using an LVD?
A failure of the LVD contactor or its control circuit can cause the load to be accidently disconnected. TDMM.* Page 9-54
172
What is the advantage of placing the LVD on the load side?
All loads will be disconnected and reconnected at the same time. TDMM.* Page 9-54
173
What is the worst-case value for output current (I out)?
Maximum output current at current limit of charger (usually 110 percent) TDMM.* Page 9-58, Table 9.5
174
How is the worst-case value for output voltage (Vout) calculated?
By multiplying the manufacturer's equalize or boost level per cell by the number of cells per battery string TDMM.* Page 9-58, Table 9.5
175
What is the worst-case value for input voltage (Iin)?
The lowest nominal voltage that is normally on the utility line TDMM.* Page 9-58, Table 9.5
176
In dc cable, how much voltage drop is allowed over the total system, battery to load?
1 V (standard practice) TDMM.* Page 9-59
177
Name the 2 most important aspects of planning the installation of a dc system.
1 .Power flow 2.Clearances TDMM.* Page 9-61
178
The bending radius must not be less than _ times the overall diameter for unshielded cables.
The bending radius must not be less than 8 times the overall diameter for unshielded cables. TDMM.* Page 9-62
179
True or False Batteries store electricity *
False. Batteries do not store electricity. They do, however, store energy in chemical form, which is converted into an electrical form during the discharge chemical reaction. TDMM.* Page 9-63
180
What is the nominal voltage of a lead-acid battery cell?
2V TDMM.* 9-63
181
What is the nominal voltage of an alkaline battery cell?
1.2 v TDMM.* Page 9-63
182
What 2 factors determine the capacity of a battery cell?
1 .Size of cell plates 2.Quantity of cell plates TDMM.* Page 9-63
183
How does connecting cells in parallel affect battery capacity?
Connecting the cells in parallel will increase battery capacity. TDMM.* Page 9-63
184
Name the 3 main types of battery cells used in telecommunications applications.
1 .Alkaline 2.Vented lead-acid (VLA) (also known as FLA) 3.Valve regulated lead-acid (VRLA) TDMM.* Page 9-63
185
Name 3 characteristics of the NiCd cell.
1 .Performs well in applications that involve temperature extremes 2.Can tolerate more abuse in terms of charging and discharging 3.Has a long life expectancy TDMM.* Page 9-63
186
What is the typical design life of a VLA cell?
10 to 20 years TDMM.* Page 9-64
187
Why is a vent included in the top cover of a VLA battery cell?
Because gases are generated during the charging process TDMM.* Page 9-64
188
Name the 2 gases produced by a VLA cell.
1 .Oxygen 2.Hydrogen TDMM.* Page 9-64
189
A minimum of — changes of room air volume per hour is recommended.
A minimum of 4 changes of room air volume per hour is recommended. TDMM.* Page 9-64
190
Why must water in a VLA battery cell be replenished?
To maintain a minimum level and ensure that all the cell plates are totally immersed TDMM.* Page 9-64
191
Do VRLA battery cells require the addition of water?
No. The NEC states: "A sealed cell or battery is one that has no provision for the addition of water or electrolyte or for external measurement of electrolyte specific gravity." TDMM.* Page 9-64
192
When does cell venting normally occur?
When the battery is subjected to overcharging or over- temperature operation TDMM.* Page 9-64
193
True or False VRLA batteries do not require any ventilation.
False. VRLA batteries do require ventilation because they release a small amount of hydrogen gas under normal operating conditions. TDMM.* Page 9-65
194
What is the typical life range of a VRLA cell?
3 to 20 years with capacities up to about 3000 AH TDMM.* Page 9-65
195
How should the typical lifespan of a VRLA battery be estimated?
By dividing the expected battery life in half TDMM.* Page 9-65
196
How can you determine the required number of battery cells?
By dividing the load nominal voltage by 2 TDMM.* Page 9-66
197
Normally, what is the manufacturer's specified input voltage "window"?
The range between the cell cutoff voltage and the cell equalized (boost) charge voltage TDMM.* Page 9-66
198
Name 4 pieces of information that is needed for battery cell sizing.
1. Direct current required in amperes at minimum voltage or load in volt-amperes or watts 2. Direct current input window of the load 3. Operating temperature of the battery 4. Battery backup time required TDMM.* Page 9-66
199
How is battery sizing in watts typically used?
For reserve times of less than an hour since the manufacturer typically presents data for short reserve times in that format TDMM.* Page 9-67
200
When is battery sizing in amperes typically used?
When reserve times of one hour and above are involved TDMM.* Page 9-68
201
What is the recommended maximum number of parallel cells in a battery plant?
5 TDMM.* Page 9-69
202
Name 2 causes of imbalance problems in parallel cells.
1 .Differences in the resistance of the paralleling connectors 2.Different resistances of each string of cells TDMM.* Page 9-69
203
What is typically the optimum temperature at which a battery should be maintained?
25 ºC (77 ºF)
204
What happens to a battery if it operates below its optimum temperature?
The battery has less capacity, but the life expectancy is extended. TDMM.* Page 9-69
205
What happens to a battery if it operates above its optimum temperature?
The battery has greater capacity, but the life expectancy is decreased. TDMM.* Page 9-69
206
Name 3 steps the ICT designer should take if it is not possible to design a battery room with a nominal temperature that approximates 25 oc (77 OF).
1 .Factor temperature compensation into the sizing calculations. 2.Employ rectifiers that will compensate the charging voltage to allow for the operating temperature of the battery. 3.Seek the manufacturer's assistance or other expert help. TDMM.* Page 9-69
207
What happens if the battery has too low a float charge voltage?
The battery will become undercharged and chemically damaged, and recharge time will be prolonged. TDMM.* Page 9-69
208
What are the effects of a too high float charge voltage?
Excessive cell gassing and plate expansion, which ultimately cause cell failure TDMM.* Page 9-69
209
True or False Wet cells may be configured on racks or housed in cabinets.
False. Wet cells should only be placed on open racks. TDMM.* Page 9-70
210
What is the minimum depth requirement for battery racks and cabinets?
1 m (3.3 ft) deep TDMM.* Page 9-70
211
Name 3 safety items that are required for locations that contain a flooded cell battery.
*Acid neutralizer (baking soda) *Eye-wash facility *Adequate spill containment in accordance with the IBC TDMM.* Page 9-70
212
Why are fused switches and circuit breakers recommended?
Fused switches and circuit breakers can be used to disconnect the battery from the rest of the power system for maintenance and repair. TDMM.* Page 9-71
213
What is the approximate value of a battery's short circuit current?
Approximately 10 times the rated AH capacity TDMM.* Page 9-71
214
What is the heart of the backup power system?
The battery TDMM.* Page 9-71
215
Define major alarms.
Major alarms are those that indicate the power system is either not functioning or is operating abnormally and is in need of immediate attention. TDMM.* Page 9-72
216
Define minor alarms.
Minor alarms are those that indicate the power system is operating in a reduced capacity or has a minor malfunction and is in need of attention. TDMM.* Page 9-72
217
Name 8 types of major alarms.
1 .Rectifier fail 2.High voltage 3.Low voltage 4.Fuse/circuit breaker 5.Inverter fail 6. Temperature 7.Monitor/control 8.Battery TDMM: Page 9-72, Table 9.7
218
What type of DC minor alarm is activated when the total load current increases above a preset limit?
Overcurrent alarm TDMM.* Page 9-73, Table 9.8
219
Name 2 types of remote alarms.
1 .Cabled remote 2.Dial-up remote TDMM: Page 9-74
220
What is the purpose of a cabled remote alarm?
To transmit power system alarms to another room or building within a relatively short distance TDMM.* Page 9-74
221
What is the purpose of a dial-up remote alarm?
To transmit alarms to a distant location usually over the telephone network TDMM.* Page 9-74
222
Name 5 features that can be controlled by a power system controller.
1 .System operating voltage 2.Prioritized load shedding on battery discharge 3. Temperature compensation 4.Boost or equalizing charging 5.Local or remote periodic testing TDMM.* Page 9-76
223
Name 2 reasons that stand- alone battery monitors become popular.
1 .Because of the importance of battery performance 2.Because the battery can be the weakest component in the system TDMM.* Page 9-76
224
In the United States, what type of conductor is color coded with green or green with one or more yellow stripes?
Equipment grounding (earthing) conductor TDMM.* Page 9-77, Table 9.70
225
In the United States, what colors are typically used to identify grounded (neutral) conductors?
White or natural gray TDMM.* Page 9-77, Table 9.10
226
In the United States, what color is typically used to identify a 208Y/120 Phase A conductor?
Black TDMM: Page 9-77, Table 9.10
227
In the United States, what color is typically used to identify a 208Y/120 Phase B conductor?
Red TDMM.* Page 9-77, Table 9.70
228
In the United States, what color is typically used to identify a 208Y/120 Phase C conductor?
Blue TDMM.* Page 9-77, Table 9.70
229
Name 2 ways that cable cores are required to be identifiable at their terminations per BS 7671.
1 .By color 2.By numbering/lettering TDMM.* Page 9-78
230
True or False BS 7671 permits over- marking in another color at terminations for multicore cables with green and yellow conductors.
True. BS 7671 permits over- marking in another color at terminations for multicore cables with green and yellow conductors, but it is prohibited for single core green and yellow conductors. TDMM.* Page 9-78
231
In the United Kingdom and Ireland, what colors are used to identify protective conductors?
Green and yellow TDMM: Page 9-79, Table 9-79
232
In the United Kingdom and Ireland, what color is used to a functional earthing conductor?
Cream TDMM.* Page 9-79, Table 9-79
233
In the United Kingdom and Ireland, what color is used to identify the phase of a single-phase circuit of a ac power circuit?
Brown TDMM.* Page 9-79, Table 9-79
234
In the United Kingdom and Ireland, what color is used to identify neutrals and mid-wires?
Blue TDMM: Page 9-79, Table 9-79
235