NEA33
POWER CONVERSION
BATTERY CHARGER CLASS
Class Chargers
MCC’s
Battery
PKA-H11
400A
PKA-M41
PKA-F11
PKC-H13
300A
PKC-M43
PKC-F13
PKA-H15
400A
PKA-M41
PKC-M43
PKA-F11
PKC-F13
PKB-H12
400A
PKB-M42
PKB-F12
PKD-H14
300A
PKD-M44
PKD-F14
PKB-H16
400A
PKB-M42
PKD-M44
PKB-F12
PKD-F14
See print 01-E-PKA-0001
8
PKA-F11 has four spare cells that are maintained on charge with
the spare Battery Charger PKN-H01.
“Bitrode” 50 amp, 18 volt
(Target Range 8.68 - 9.00 Vdc)
Each backup charger has two output breakers to enable them to supply
DC power to either bus (A or C and B or D) it serves. A mechanical
interlock is provided between the breakers which prevents possible
closing of both of the breakers simultaneously.
How long can the Class 1E Batteries supply power
continuously to class loads ?
• The Batteries will provide 2 hours of 125 VDC
power continuously to all class IE electrical
loads connected to the system.
• If the inoperable DC electrical power subsystem
cannot be restored to OPERABLE status within
the required Completion Time, the unit must be
brought to at least MODE 3 within 6 hours and to
MODE 5 within 36 hours
• During modes 1 through 4, both DC trains
consisting of all four control centers consisting
of all four batteries and four battery chargers,
are operable and energized to meet the Tech
Spec requirements.
• During modes 5 and 6, at least one train
consisting of two control centers, including
batteries and battery chargers, is operable
and energized to meet the Tech Spec
requirements.
Design Basis for Class 1E Chargers:
• Restore the batteries to their fully charged state
condition within 12 hours regardless of plant
condition, starting from a minimum battery design
charge of 105 VDC.
Some of the DC loads for PK:
•
DC power to the PN Inverters (Vital AC)
•
DC power to the PK Inverters (Shutdown Isolation Valves)
•
Reactor Trip Switchgear Control Power
•
Diesel Generator Control And Starting Circuit
•
Aux Feedwater Turbine Governor Control Panel
•
DC Control Power for PB and PG
•
Auxiliary Feedwater Pump A Turbine Trip And Throttle Valve
•
Aux Relay Panels
•
Other critical DC valves
125V DC non class IE power system (NK)
The non class IE 125V DC power system consists of three
independent non class IE 125V DC subsystems. Each
subsystem (E, F, G) has a battery, 125V DC control center
and/or 125V DC distribution panels and a battery charger
supplied with 3 phase 480V AC power from a different MCC.
Supplies 125V DC power to in-plant DC loads through MCC’s
NKN-M45 and NKN-M46 and “D” panel NKN-D19.
NON-CLASS BATTERY CHARGERS
NKN-H17
(E) Battery Charger Norm. Feed NKN-M45
500 amp
NKN-H18
(F) Battery Charger Norm. Feed NKN-M46
250 amp
NKN-H19
(G) Battery Charger Supply to
50 amp
NKN-D19
NKN-H20
(E1) Battery Charger Alt. Feed
500 amp
NKN-M45
NKN-H21
(EF) Battery Charger Alternate to M45/M46
500 amp
SEE PRINT 01-E-NKA-0001
Normal lineup is the “F” Battery Charger NKN-H18 feeds
NKN-M46 and the “E” Battery Charger NKN-H17 feeds
NKN-M45.
NKN-H18 is a 250 amp charger, smallest charger with
the largest Battery (3650 AH)
Each non class IE battery has sufficient capacity to
independently supply the required loads for 4 hours
following the loss of battery charger.
NKN-F17
NKN-F18
The backup charger (“EF”) has two output breakers to enable
them to supply DC power to either bus (M45 or M46) it serves. A
mechanical interlock is provided between the breakers which
prevents possible closing of both of the breakers simultaneously.
Easy way to
remember what
480 volt MCC
feeds the swing
charger. NHNM21 feeds NKNH21.
14
Some of the DC Loads for NK:
Main Turbine Emergency Lube oil Pumps (EBOP)
Main Turbine Seal Oil Pumps (SO)
Control Power for NA, NB, MA, Switchgear and Transformers.
(Includes protection relays).
Control power for NG
DC Power to the Plant computer (NQ)
Control Power to Diesel Generator
Trip circuit for Main Turbine
Control Power to Aux. Relay panels
Feedwater Trip and Reset control circuit (FW)
15
EO02 – Identify the Battery Charger Power Circuit Components.
16
Power Circuit
17
The AC input Circuit
Breaker CB1
Main transformer (T1)
Back View
Front View
T1A
T1C
T1B
Fuses for the main SCR's (F1-F6)
Each of the six power SCR’s are fused to protect it from a high overload.
SCR’s
Free Wheeling
Diode CR7
CR6
CR4
CR5
CR3
Blocking
Diode CR8
CR2
CR1
(MOV’s) Metal Oxide Varistor's (D1-D7): Protect
SCR’s (CR1 – CR6) and Freewheeling diode (CR7
Dc filter (L1, C1, and R1)
R1
C1
L1
RS1 Shunt to
Local Ammeter
And A2 & A3 boards
RS2 Shunt to
Remote Ammeter
And alarm module
The DC output circuit breaker
(CB2): Used as a switch only
Back-up chargers have two
output breakers (CB2A and
CB2B)
CB1
CB2
EO03 Explain the function of the components in the
battery charger’s power circuit.
Power is fed to the input transformer (T1). T1 is a three-phase delta
to delta transformer. T1 provides power to the main SCR's and the
120VAC power to the Amplifier Board, and the Firing Module.
T1 also supplies power to
all of the accessories,
such as the power on
indicator, the AC failure
alarm (K3 relay) the three
phase power monitor
(K1) and the 0-24 hour
timer motor.
Review Prints E051-00018 and E051-00033
27
The firing module receives the error signal from the Amplifier
Board and determines how long the SCR’s need to fire for
voltage correction.
A1
Control Circuit
-10 vdc
Common
+ 10 vdc
120 volt input from T1
30
A3
34
Control Circuit
-10 vdc
Common
+ 10 vdc
120 volt input from T1
35
Non-Class Charger
Class Charger
CHARGER OPERATING CURVE
2.75
VOLTS PER CELL
2.50
EQUALIZE
FLOAT
2.25
2.00
102%
1.75
105%
1.50
0
20
40
60
80
100
% CHARGER CURRENT
120
140
38
NOTE: Polarity across the load
Resistor (RL) does not change.
NEA07
Slide 28
40
Polyphase alternating current, when rectified, gives a much “smoother” DC
waveform (less ripple voltage) than rectified single-phase AC.
Alarm Module
“59”
“27C” “37”
“32”
45
46
48
Alarm Module
The battery charger’s alarm module contains four (4) alarm
circuits on printed circuit boards that are connected to a
mother board. The DC Relay on each Alarm board actuates
the (K-2) Summation Alarm. All of the cards have an LED
that indicates as follows:
ALARM CARD
Reverse Current
Charger Failure
Low Voltage
High Voltage
NORMAL
LED off
LED on
LED on
LED off
ALARM
LED on
LED off
LED off
LED on
Note: the LED on the Charger Failure Alarm Board will be in
alarm condition until the Battery Charger senses a load on the
bus.
50
ALARM MODULE RELAY CONTACT
SCHEMATIC
RCA in alarm, Shunt
polarity changed.
RCA in Alarm Condition, LED on,
Q1 & K1 is picked up.
CFA in Non Alarm Condition, LED
On, Q1 & K1 is Picked up.
Testing SCR’s
Lift the white gate lead and red cathode lead on each SCR and
take a resistance reading between the two. Reading should be
less than 50 ohms.
Larger Power SCR’s
have a resistor between
The Gate and Cathode
Used to prevent false triggering
SCR’s Cont..
Using a lamp tester, attach the Positive (+) to the anode and the
negative to the Cathode.
Gate the SCR on by touching the positive to the white gate lead.
The lamp should be brightly illuminated.
Remove the signal and verify that the SCR stays on.
Apply a second gate pulse and verify the SCR stays on.
Test SCR’s on the Lab Charger
Replacing SCR’s
New SCR’s are tested prior to installation
SCR leads may have to be extended; splicing instructions are in work
package.
Observe proper polarity when installing.
Apply a thin film of heat sink compound on the conducting surface on
the new SCR.
Ensure alignment pin in charger is aligned with the indent in the SCR.
Perform Torque/Clamping for specific SCR to be replaced.
Ensure alignment pin in charger is
aligned with the indent in the SCR.
SCR’s have been found damaged
due to misalignment during
clamping.
EO09 Given a Fault condition, troubleshoot/rework the Battery
Charger and discuss safe work boundaries and electrical safe
work practices necessary to perform the task.
Human Performance Tools when working on the Battery Charger
Follow procedures and work instructions
Stop when unsure or in the face uncertainty
Use operating experience to prevent errors
Perform a good pre-job brief
Perform a 2-min drill
Use self-check and peer-check
Three-Way communication
Provide good turnovers
Perform a post job brief
On Non-Class Chargers, ensure the force paralleling wire is
lifted prior to working on the charger.
Troubleshooting Techniques:
Battery Charger symptoms
A symptom is a sign or indicator of some malfunction of the equipmen
Use your senses of hearing, sight and smell
Perform a visual inspection
Check alarm condition
Check voltage/current output of Battery Charger
Document findings
Localizing the Faulty Function:
Think Block Diagram when troubleshooting
Is it a Control or Power problem?
Power Circuit:
Power Fuses
SCR’s/Diodes
Tripped AC Breaker
Filter network ,Capacitors, R1 resistors and inductor L1
Transformer
Control Circuit:
Float/Equalize voltage network
Sensing & Current Limit board
Amplifier Board
Firing Modules
Control Fuses
Alarm Circuit
What drops out the K2?
Some of the tools used for troubleshooting:
Fluke DVOM
Fluke Scope or Astro-Med
Amp Probe
SCR test light
Mini grabber test leads
Flashlight
Small pin point test leads
Load Bank if required
64
During troubleshooting use the provided table to compare
voltage readings taken at various points on the Sensing and
Current Limit Board and the Amplifier Board.
AMPLIFIER BOARD
VTD P319-002
TERMINAL BOARD
POINT
APPROXIMATE DC
VOLTAGE
AS FOUND DC
VOLTAGE
REMARKS
6, 7, 8
Common
Common
Common
10
1.7 to 2.9 Vdc
9
10.25 Vdc
5
4.0 to 4.3 Vdc
11
13
14
12
-10 Vdc
-2.91 Vdc
+ 30mv to -10mv
2-4 Vdc
Varies With output voltage
Effects output voltage
Varies With Float or Equalize Voltage Adjust (R3,R6)
Effects Current Limit
Varies With Current Limit Setting (R9)
Varies Directly With Output Current
Varies With Output Current and Input Voltage (Line)
SENSING AND CURENT LIMIT BOARD
PIN
NUMBER
APPROXIMATE DC
VOLTAGE
AS FOUND DC
VOLTAGE
REMARKS
4
-2.91 Vdc
5
COMMON
Across CR9
5.3 Vdc
Any deviation indicates a faulty sensing module.
Across CR11
5.3 Vdc
Any deviation indicates a faulty sensing module.
Across R5
14.1 Vdc
Any deviation indicates a faulty sensing module.
Current Reference Depending on R9 Settings
COMMON
COMMON
8
10.25 Vdc
Develops Voltage Reference
7
1.7 to 2.9 Vdc
Voltage Variable
2
+ 30mv to - 10mv
3
10
12
- 10 Vdc
Current Variable
Develops Current Reference
4.0 to 4.3 Vdc
Voltage Reference
4.7
Output voltage to Cabinet mounted Components
Voltage Problem
Example: No DC output
Check pin 12 (output to the firing modules), should be between 2-4 Vdc
Check A2 Amp board for power supply voltages, +10.25 and – 10 vdc
Check voltage reference at pin 5 to common, should be approx. 4.3 Vdc
Check common on the Float/Equalize Switch, reading should be approx. 4.3 Vdc.
Check pin 12 on the S&C Limit board
Check R8 on the S&C Limit board
Check control fuses
Ask the class if they can think of any thing else
Regulation Problem
Example: Charger noisy when loaded
SCR’s may not be firing properly
Check gate signals to SCR’s on each module
Check AC input to each firing module
Check soldering connections
Check current through main fuses
Alarm Problem:
Example: Summation Alarm in the Control Room
K2 relay should be dropped out
Verify alarm condition of alarm cards
Check 3 phase power monitor
Check control fuses
Check K4 relay
During outages it is not uncommon for one of the DC
buses not to have a load. The CFA alarm will come in if
current is less than 5 Amps.
CRDR 3233151 found incorrect fuses
installed in 1ENKNF17, fuses F11, F12,
F13 and F14 size 1/8 Amp fuses instead of
1 Amp.
Current Limit Problem:
Check verify R9 setting (S & C Limit board)
Check verify Current variable during operation
P3 may have to be adjusted on the Amp board
Check current reference (- 2.9 Vdc or lower)
Check verify output on pin 12 to firing modules (2-4 Vdc)
SME – It helps to monitor current reference at point 13
on the amp board while adjusting R9. This helps the
tech determine direction of adjustment. The lower the
setting, the lower the current limit.
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