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14th Reading > Chp 9 Power Distribution > Flashcards

Chp 9 Power Distribution Flashcards

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:

A

VIefficencypower factor2/746

24
Q

HP of a three phase ac power signal is calculated:

A

VIefficencypower factor1.73/746

25
Q

Voltage drop is calculated

A

Vdrop = 2KLengthCurrent/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
Q

IG is intended to decrease the effects of EMI and RFI on the equipment grounding system, but should NOT be used with ________ systems

A

Isolated grounding….. should not be used with voice and data

27
Q

Wherever possible, telecommunications equipment should be powered from a panelboard that does not have an inductive load and on a circuit with a _______ feeder

28
Q

To convert circular mills to square mills

A

multiply by 0.7854

29
Q

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

30
Q

The _____ (in mills) squared is equal to the area in circular mills of the conductor

31
Q

In ac circuits, the change in current causes issues with the _______ of voltage

32
Q

Conductor cross-sectional area in squared inches can be found by multiplying the C. mills by _____

A

pi/4 (or 0.7854)

33
Q

Busbar circular mills cross sectional are can be found using this calculation:

A

Thickness1000 * Width1000 * 0.7854

34
Q

AC power can have distortions in the form of:

A

voltage, current, and frequency fluctuations, and noise

35
Q

Transients/surge

A

A momentary (but significant) fluctuation in voltage or current that lasts less than 0.5 of a cycle (or 8.3ms)

36
Q

Swell

A

An increase in voltage or current lasting from 0.5 cycles to 1 minutes

37
Q

The opposite of a swell is known as a _____

38
Q

A decrease in the nominal voltage for more than 3600 cycles (on minute)

A

undervoltage

39
Q

An increase in the nominal voltage for more than 3600 cycles (one minute)

A

Overvoltage

40
Q

Interruption

A

the total absence of voltage on one or more phase conductors for a period of time

41
Q

Harmonics are

A

replicas of signal caused by switching power supplies

42
Q

Standard setting 5% the maximum allowable total harmonic distortion of the voltage waveform

43
Q

Common mode noise

A

Noise present between the phase and ground, or neutral and ground

44
Q

Differential mode noise (aka normal mode noise)

A

noise present between the phases and between the neutral and phase

45
Q

When is a neutral conductor required to be sized 200% of phase lines?

A

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
Q

What is a the term for a neutral conductor that is required to be sized at 200%?

A

current-carrying conductor

47
Q

What is the maximum current a neutral conductor can carry when powering single phase switching power supply units?

A

1.73 * the phase line current

48
Q

Power Distribution systems, as they apply to Information Technology Equipment, are made up of the following components:

A

Panelboards, PDUs, and RPPs

49
Q

Which component of the ITE Power Distribution System consists of multiple OCPDs and is responsible for the distribution of power?

A

panelboards

50
Q

What is the function of an OCPD?

A

to protect the load equipment in the event of short circuit or overcurrent

51
Q

How many types of OCPDs are there, and what are they?

A

2; fuses and breakers

52
Q

Typical OCPD device used in the telecom/data industry for telecom/data equipment

A

Circuit breaker

53
Q

Typical circuit breaker sizes and voltages used in communications equipment

A

20-60A

120V 1-phase and 208V 1-phase, although 208V 3 phase is being increasingly utilized

54
Q

PDU is

A

Power distribution unit: consists of a surge supression device, transformer, panelboards, single-point ground, and capable of having individual branch circuit loads monitored.

55
Q

PDUs are advantageous because

A

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
Q

RPPs are

A

the same as a PDU but without the transformer

14th Reading (13 decks)

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