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2B > DC System > Flashcards

DC System Flashcards

1
Q

station battery charger failure light

A

if output current falls to below 2% of rated output current for more than 30 seconds

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2
Q

fully discharge battery formula

A

PbSO4 + PbSO4 + 2H2O
(-) (+) (water)

PbSO4 = Lead sulfate

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3
Q

fully charged battery formula

A

Pb + PbO2 + 2H2SO4

-) (+) (liquid

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4
Q

control room battery charger ammeter

A

0 - 100 A

Normally 30A

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5
Q

VM and AM on station battery charger

A

VM - 0-200V 135V floating

AM - 0-75A 20-25A

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6
Q

station battery charger
High AC Volt High DC Volt
Low AC Volt Low DC Volt

A

High AC - 115% High DC - 144V

Low AC - 85% Low DC - 120V

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7
Q

control room 125V battery bus voltmeter

A

digital 135V +/- 1V

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8
Q

control room 125V battery voltmeter

A

0 - 150 V

Normal 135V

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9
Q

control room station battery ammeter

A

-100 - 300
normal just to - side of 0 (trickle charge)
- charging
+ carrying load

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10
Q

control room ac distribution main bus voltmeter

A

0 - 150V

normally 116V

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11
Q

control room ground detecting voltmeter

A

-150 - 150V
Should be 0
tells how hard the ground is

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12
Q

ground detector 125V bus annunciator

A

D-3 relay +- 50mA

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13
Q

control room 48V DC system voltmeter

A

0-60V

normally 54V

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14
Q

control room ground detector test switch

A

+ and - test switch

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15
Q

resistors are set so ground detector VM and D3 indicate same thing

A

.

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16
Q

VM and AM on supervisory battery charger

A

VM 0-80 54V normal

AM 0-50 20A normal

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17
Q

AC relays pickup value

A

85% rated V

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18
Q

DC 125V relay pickup and drop out

A

pickup is 80% ~100V - at 100V relays may not pick up

dropout is 70% ~85V - at 85V normally picked up relays will start to drop out

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19
Q

control room ac distribution main bus ammeter

A

0-50A 25A

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20
Q

battery room low ventilation

A

air flow switch

63BRA @ no air flow

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21
Q

do we use the battery chargers ground detection

A

no, we use our own D3

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22
Q

specific gravity

A

strength of concentration of electrolyte
weight of a volume of a substance
————————————————–
weight of an equal volume of fresh water

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23
Q

what is a pilot cell

A

weakest cell in the bank

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24
Q

why do you select a pilot cell

A

to indicate the general condition of the entire batter bank in regard to voltage, specific gravity, and temperature

25
Q

how is the pilot cell determined

A

by specific gravity, voltage, and temperature

determined initially and confirmed or changed quarterly

26
Q

what measurements does a digital hydrometer give you

A

specific gravity & temperature

27
Q

if you have to add distilled water to a cell, how long does it take to mix so you get an accurate specific gravity reading?

A

6 weeks or more unless you perform an equalizing charge

28
Q

when can you add electrolyte

A

when it is known that the electrolyte was spilled from a cell

29
Q

what is the electrolyte we use

A

diluted sulfuric acid

30
Q

what charge does the trickle charge (float) keep our batteries at?

A
  1. 23V/Cell

134. 7 V DC (135V)

31
Q

how fast to recharge?

A

not any faster than it was discharged

32
Q

equalizing charge

A

2.33V/cell until charging current stabilized of 4 consecutive hours
for a minimum of 35 hours for lead antimony
max of 72 hours
done when specific gravity and voltage hasn’t changed for 2 hours

33
Q

while recharging, current will break down water in electrolyte to H and O which are given of in the form of gas

A

.

34
Q

when should equalizing charge be given

A

if any cell falls below 2.13V, or rises above 2.38V corrected for temp
when corrected specific gravity has fallen more than 10 points
at least once every 24 months

35
Q

correcting voltage for temp

A

voltage of a warm cell is lower

add .003V for each degree F that the cell is above average temp of other cells, subtract if cooler

36
Q

what type of cells do we have

A

single vented tubular cells

37
Q

what are the 2 groups of coated lead plates in a battery

A

positive and negative electrodes

38
Q

do batteries have an even number of plates

A

no, always have 1 extra negative plate

39
Q

what determines the number of cells used

A

total voltage required

40
Q

what does the current supplied by a storage battery depend on

A

it’s voltage, physical condition, & resistance of the load circuit

41
Q

what determines the resistance of a battery

A

the condition of the electrolyte, the size of the plates, and the # of plates

42
Q

what limits the max current of a battery will supply

A

the internal resistance of the cell

43
Q

a storage cell consists of

A

a group o positive plates connected, a group of negative plates connected, separators, electrolyte, suitable container

44
Q

what does voltage of a cell depend on

A

the material of he electrodes and electrolyte

45
Q

+ plate

- plate

A

lead dioxide

sponge lead

46
Q

what is generated at + and - plate

A

+ oxygen gas

- hydrogen gas

47
Q

types of storage battery

A

stationary or portable

lead acid/nickel-iron-alkaline/nickel-cadmium

48
Q

battery PPE

A

goggles and face shield appropriate to the chemical and electrical hazard
acid resistant rubber gloves
protective rubber apron and safety shoes
lifting devices of adequate capacity when required

49
Q

what periodic inspection do we have

A

daily - visual
weekly
quarterly
5 year load test - load batteries for 8 hrs @ AH rating, 1st hour take readings (SG, V, Temp) every 15 mins, next 6 hours take readings ever hour, last hour take readings every 15 mins

50
Q

initial records

A

battery terminal float voltage
SG of each cell corrected to 25* C
individual cell voltages
electrolyte level
temp of one cell on each row of each rack
cell to cell and terminal connections, resistance readings

51
Q

weekly maintenance

A

observe appearance and cleanliness
read and record charger output A and V
observe electrolyte levels
check for cracks in cells or leakage of electrolyte
check for evidence of corrosion at terminals or connections
check ambient temp and condition of ventilating equipment
read and record pilot cell V, Temp, and SG
read and record battery terminal voltage

52
Q

quarterly maintenance

A

SG of each cell
V of each cell
battery terminal voltage (compare control room to battery charger VM)
temp of one cell on each row or rack
detailed visual inspection of each cell and integrity of rack

53
Q

Station battery nameplate

A 
Powersafe
6 opzs600
60 cells - 13 plates per cell (7-,6+)
2.23V per cell
1.24 kg/L specific gravity at 20*C
648 amp hour at 8 hour rate
Diluted sulphuric acid
54
Q

Station battery charger nameplate

A 
GNB
Type SCR
AC Input
3 phase 60 cycle
480V 16A
DC Input
130V 50A
85mV ripple
55
Q

Items on station battery charger

A 
DC VM 0-200V @135V Floating
DC AM 0-75A @20-25A
Red Lights     
High AC V     High DC V 2.4V/cell     
Low AC V      Low DC V 2.0V/cell     
Charger failure light     
Positive ground detector     
Negative ground detector
Toggle switch for load sharing connection to split the load
Toggle switch to switch between floating and equalizing charges
Floating charges set screws
Equalizing charge set screws
Lamp test push button
Relay reset push button
56
Q

Supervisory battery nameplate

A 
Varta
VB4118
24 cells - 17 plates/cell (9-,8+)
2.23V per cell
268 amp hour
1.24 kg/l specific gravity at 20*C
Diluted sulphuric acid
57
Q

Supervisory battery charger nameplate

A 
GNB
AC Input
3 phase 60 cycle
480V 8A
DC output
48V 50A
30mV ripple charge
58
Q

Items on supervisory battery charger

A

DC VM 0-80V @54V

DC AM 0-50A @26A

59
Q

Inverter set nameplate

A 
LaMarche
Type A31
DC Input
120V
12A No Load
105A Full Load
AC Output
120V
83.33A 
10KVA

2B (3 decks)

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