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14th Reading > Chp 9 Power Distribution > Flashcards

Chp 9 Power Distribution Flashcards

(56 cards)

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1
Q

Phase

A

Signal’s time domain

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2
Q

Delta Configuration

A

three phase configuration with three conductors, with each phase 60 degrees apart.
Output voltages: 120VAC, 240VAC

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3
Q

Wye Configuration

A

three phase system with a four conductor configuration (fourth conductor is center tap, neutral)
Vout: 120VAC, 208VAC

Measured from phase to neutral, therefore 208V/ sqrt(3) = 120VAC

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4
Q

residential phase configuration

A

Center-tapped Single Phas.
180 degrees out of phase
120/240

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5
Q

Electrical system between the serving utility and the customer’s site is known as the _______________ system

A

distribution

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6
Q

Customer’s site, aka _______

A

service point

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7
Q

Various equipment is a.k.a.______________

A

loads

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8
Q

Electrical wiring system is…

A

the cabling between the distribution system’s connection at the service point and the loads it powers

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9
Q

Net reactance

A

the difference between the capacitative and inductive reactance

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10
Q

A purely resistive circuit has the current and voltage ______

A

in phase

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11
Q

________ causes a lag time between voltage and current waveforms

A

Inductive reactance (inductance)

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12
Q

A capacitative load causes _________________

A

current to lead voltage

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13
Q

Power factor is

A

the ratio of real power to apparent power

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14
Q

Apparent Power is

A

the product of measured amperage and voltage denoted in VA

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15
Q

Real power is

A

determined by approximating effects of inductance and capacitance.
measured in Watts

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16
Q

Output power / Input Power

A

efficiency

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17
Q

1 ton of cooled air per _____ watts or ______ Btus

A

3517W, 12000Btu

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18
Q

Regulation specifying wiring identification in UK

A

BS 7671

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19
Q

Horse Power is a mechanical unit of _______

A

Power

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20
Q

HP calculation is dependent on the type and _____ of current.

A

phase

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21
Q

DC HP is calculated

A

VIefficiency/746

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22
Q

HP of a single phase ac power signal is calculated:

A

VIefficiency*power factor/746

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23
Q

HP of a double phase ac power signal is calculated:

Study These Flashcards
A

VIefficencypower factor2/746

24
Q

HP of a three phase ac power signal is calculated:

Study These Flashcards
A

VIefficencypower factor1.73/746

25
Voltage drop is calculated
Vdrop = 2K*Length*Current/circular mills *delta where delta = 1/2 for 3 phase 4 conductor circuit =0.866 for 3 phase 3 conductor = 1 for single phase
26
IG is intended to decrease the effects of EMI and RFI on the equipment grounding system, but should NOT be used with ________ systems
Isolated grounding..... should not be used with voice and data
27
Wherever possible, telecommunications equipment should be powered from a panelboard that does not have an inductive load and on a circuit with a _______ feeder
dedicated
28
To convert circular mills to square mills
multiply by 0.7854
29
AWG wiring sizes are based off of a geometric progression of the previous size. Starting with ____, the size (in circular mills) decreases by a factor of 0.890525
4/0
30
The _____ (in mills) squared is equal to the area in circular mills of the conductor
diameter
31
In ac circuits, the change in current causes issues with the _______ of voltage
quality
32
Conductor cross-sectional area in squared inches can be found by multiplying the C. mills by _____
pi/4 (or 0.7854)
33
Busbar circular mills cross sectional are can be found using this calculation:
Thickness*1000 * Width*1000 * 0.7854
34
AC power can have distortions in the form of:
voltage, current, and frequency fluctuations, and noise
35
Transients/surge
A momentary (but significant) fluctuation in voltage or current that lasts less than 0.5 of a cycle (or 8.3ms)
36
Swell
An increase in voltage or current lasting from 0.5 cycles to 1 minutes
37
The opposite of a swell is known as a _____
sag
38
A decrease in the nominal voltage for more than 3600 cycles (on minute)
undervoltage
39
An increase in the nominal voltage for more than 3600 cycles (one minute)
Overvoltage
40
Interruption
the total absence of voltage on one or more phase conductors for a period of time
41
Harmonics are
replicas of signal caused by switching power supplies
42
Standard setting 5% the maximum allowable total harmonic distortion of the voltage waveform
IEEE 519
43
Common mode noise
Noise present between the phase and ground, or neutral and ground
44
Differential mode noise (aka normal mode noise)
noise present between the phases and between the neutral and phase
45
When is a neutral conductor required to be sized 200% of phase lines?
When line currents contain third and multiple uneven harmonics. This is caused by switching power supplies in telecom/data equipment that requires single phase power being powered by a three-phased supply.
46
What is a the term for a neutral conductor that is required to be sized at 200%?
current-carrying conductor
47
What is the maximum current a neutral conductor can carry when powering single phase switching power supply units?
1.73 * the phase line current
48
Power Distribution systems, as they apply to Information Technology Equipment, are made up of the following components:
Panelboards, PDUs, and RPPs
49
Which component of the ITE Power Distribution System consists of multiple OCPDs and is responsible for the distribution of power?
panelboards
50
What is the function of an OCPD?
to protect the load equipment in the event of short circuit or overcurrent
51
How many types of OCPDs are there, and what are they?
2; fuses and breakers
52
Typical OCPD device used in the telecom/data industry for telecom/data equipment
Circuit breaker
53
Typical circuit breaker sizes and voltages used in communications equipment
20-60A | 120V 1-phase and 208V 1-phase, although 208V 3 phase is being increasingly utilized
54
PDU is
Power distribution unit: consists of a surge supression device, transformer, panelboards, single-point ground, and capable of having individual branch circuit loads monitored.
55
PDUs are advantageous because
they have a smaller foot print and can power just as much equipment, but with cleaner power due to its: - higher voltage input feeder (allows it to handle the voltage drop better) - surge suppression - K rated transformed to handle heating effects of harmonic producing equipment
56
RPPs are
the same as a PDU but without the transformer

14th Reading (13 decks)

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