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Power System
Considerations for
CENTERLINE® 2100 Motor
Control Center Selection
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
Agenda
1. Introduction
2. Power System Configurations
3. Disconnecting Means
4. Unit Selection
5. Neutral Bus and Neutral Options
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
2
Introduction
• Today’s discussion will focus on
– Power system configuration characteristics
– Selection of CENTERLINE® 2100 motor
control center (MCC) sections and units with
respect to these characteristics
– Neutral bus and neutral bus options available
in CENTERLINE 2100 MCCs
• Other important MCC selection criteria,
not discussed today, include
–
–
–
–
–
Codes and standards
Total load
Environment
HP, voltage, load characteristics
Load current ratings
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
3
CENTERLINE 2100 MCCs Capabilities
• The quick delivery product offering
supports the following power systems,
rated 600 V or less, 50 or 60 hertz
– Wye, 3-phase, 3-wire,
with a solidly grounded neutral
– Wye, 3-phase, 4-wire,
with a solidly grounded neutral
– Wye, 3-phase, 3-wire,
with an impedance grounded neutral
– Delta, 3-phase, 3-wire, ungrounded
• The custom engineered delivery
program offers support for other power
systems configurations, including
– Delta, 3-phase, 3-wire,
"corner" grounded (Grounded “B” Phase)
– Delta, 3-phase, 4-wire,
center-tap-grounded, (“high-leg“)
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
4
Requirements for Power System
Configuration Information are Increasing
• More and more selections are dependent on power system configurations
– If power system configuration data is not correct, improper configurations may not be
apparent to the factory
• Example 1: The power system is an ungrounded Delta and the MCC has a 600 A main
circuit breaker with internal ground fault protection
– A ground fault grounds the system, producing very low ground fault current (less than 10 A).
Ground fault protection won’t trip the breaker! (in this example need minimum 120 A)
• Example 2: The power system is a impedance grounded Wye and the MCC has
PowerFlex drive units
– Need to isolate drive surge protective circuits from ground
• Example 3: The power system is a solidly grounded Wye and the MCC has a 2000 A
main circuit breaker which includes a neutral connection plate
– If a full rated neutral is going to be brought to the MCC, a neutral connection plate may not be
able to accommodate size and quantity of incoming neutral cables
Power system configuration information is essential to help ensure
proper selection of MCC sections and units
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
5
Power System Configuration Questions
• Obvious questions
– Voltage? Frequency?
Available Short Circuit Current?
• Not so obvious,
but important questions
–
–
–
–
–
–
Is system configured as Wye?
Is it Delta?
Is it ungrounded?
Is it impedance grounded?
Is it solidly grounded?
Is there a neutral wire?
• Is it being brought to the MCC?
• Is a horizontal neutral bus
required?
• Are there line-to-neutral loads?
– Is any load more than 280 A?
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
6
Agenda
1. Introduction
2. Power System Configurations
3. Disconnecting Means
4. Unit Selection
5. Neutral Bus and Neutral Options
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
7
Power System Configurations
• Proper selection of MCC sections and units requires awareness of
different types of power system configurations
• Two basic systems used to feed MCCs – Delta and Wye
3-Phase Wye
3-Phase Delta
– Wye or Delta cannot be determined if only three phase conductors are used
• Even if there is a neutral conductor, the power system might be Delta
• Power systems may be ungrounded, solidly grounded, or impedance
grounded
– The presence of an equipment grounding conductor does not give any information
about the power system grounding
• Power systems that are solidly grounded may have a neutral
– If a neutral is used, then line-to-neutral loads may be present
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
8
Delta Connected Power System
Ungrounded
• 3-wire only
• Ground detection system is required
• Allows continuity of power in the
event of a line-to-ground fault
– Fault only grounds the system
– Very low current would flow
– Circuit breakers and fuses will not open
• Line-to-ground voltage could exceed
line-to-line voltage by several times
due to transients or other abnormal
conditions
• Typical system voltages
– 240V
– 480V
– 600V
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
9
Wye Connected Power System
Ungrounded
• 3-wire only
– Line-to-neutral loads cannot be used
• Ground detection system is required
• Allows continuity of power in the
event of a line-to-ground fault
– Fault only grounds the system
– Very low current would flow
– Circuit breakers and fuses will not open
• Line-to-ground voltage could exceed
line-to-line voltage by several times
due to transients or other abnormal
conditions
• Typically not used for new
installations
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
10
Delta Connected Power System
Corner-grounded (Grounded “B” Phase)
• 3-wire only
• Grounding one phase stabilizes
line-to-ground voltage at line-toline voltage
• Less susceptible to voltage rises
due to transients or other
abnormal conditions
• Circuit breakers usually cannot be
used
– Low interrupting ratings for fullvoltage line-to-ground fault on a
single-pole
• Typically not used for new
installations
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
11
Wye Connected Power System
Solidly Grounded
• Most commonly used Wye
– Like all Wyes, each phase shares a
common neutral point
• 3-wire system if neutral is not used
• 4-wire system if neutral is used
– Can serve line-to-neutral loads
• Typical system voltages
– 208Y/120 V
– 480Y/277 V
– 600Y/347 V
• A line-to-ground fault could cause
high current to flow, open circuit
breakers or fuses, resulting in
power interruption
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
12
Wye Connected Power System
Impedance Grounded Neutral
• 3-wire only
– Line-to-neutral loads cannot be used
• Ground detection system required
• Impedance selected to limit line-toground fault current
– Typically 10 A or less
• Reduces incident energy for line-toground arcing faults
• Becoming a more popular system
where continuity of power is critical
– Low level of line-to-ground fault current
will typically not cause circuit breakers or
fuses to open
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
13
Delta Connected Power System
“Center-tap” Grounded
• 4-wire
– Can serve line-to-neutral loads
• Typical line-to-line voltage 240 V
– Line-to-neutral voltage 120 V from
either side of the tap
• Phase opposite tap is referred to
as “high-leg”
– Line-to-neutral voltage 208 V from
“high-leg”
• “High-leg” must be marked when
present with the neutral
– Reduces chance of connecting
120 V line-to-neutral load to 208 V
“high-leg” to neutral
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
14
“Open” Delta Connected Power Systems
• Typical utility customers may need only
1-phase, 3-wire, 120/240 V
– Provided by one, single phase, typically
center-tap-grounded transformer
• For 3-phase, the utility may provide
another single-phase transformer
– Connected to form an “open” Delta
– Load capacity is lower than closed Delta
– Less equipment cost compared to three,
single-phase transformers
– Still provides 3-phase voltage
– This example is a 4-wire “high-leg” system
For the selection of MCC sections and units,
“open” Delta can be treated as closed Delta
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
15
Agenda
1. Introduction
2. Power System Configurations
3. Disconnecting Means
4. Unit Selection
5. Neutral Bus and Neutral Options
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
16
Disconnecting Means
• Needed for any unit which either feeds
the MCC bus or is fed from the bus
• Usually include overcurrent protection
– Short circuit
• Fast acting, “magnetic” protection
– Overload
• Inverse time, “thermal” protection
• Two types available
– Circuit breakers
– Fusible switches
• Selection depends on
– Power system configuration
– User preference
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
17
Circuit Breakers
• Selection criteria are
– Voltage rating
• Wide variety of circuit breakers with different ratings available
– Short circuit (SC) interrupting rating
• Typically three to four options available, ranging from 14 kA to 100 kA
– Trip unit type
• Thermal/Magnetic or Electronic
• Standard MCC units
–
–
–
–
Use molded case circuit breakers (UL 489)
Have “straight” voltage ratings which match the system voltage*
400 A frame and smaller use thermal/magnetic trip units
600 A frame and larger use electronic trip units
• Combination motor controller units use Motor Circuit Protectors
• Main circuit breakers sometimes are power circuit breakers (UL 1066)
* Lighting panel and panelboard unit branch breakers are slash rated
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
18
Circuit Breakers –
Voltage Ratings
• Ratings are given “straight” or “slash” voltages
– ‘Straight” ratings, e.g. 240 V, 480 V, 600 V
• Line-to-line voltage must not exceed the voltage rating
• Can be used on all power systems*
– “Slash” ratings. e.g. 120/240 V, 480Y/277 V, 600Y/347 V
• Smaller voltage is maximum line-to-ground voltage
• Larger voltage is maximum line-to-line voltage
• Power system must be solidly grounded
– Wye with solidly grounded neutral
– Delta with solidly grounded, center-tapped neutral
– Delta with solidly grounded corner*
• Circuit breakers may have both “slash” and “straight” voltage ratings
• Short circuit (SC) interrupting rating is voltage dependent
– SC ratings may vary for the same circuit breaker at different voltage ratings
* Interrupting ratings for corner grounded Delta may be too low for practical MCC use
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
19
Circuit Breakers –
Single-pole Short Circuit Interrupting Rating
• Article 240.85 of the NFPA 70 “National Electric Code®,” includes a fine
print note regarding circuit breaker applications
– "FPN: Proper application of molded case circuit breakers on 3-phase systems, other
than solidly grounded wye, particularly on corner grounded delta systems.
Considers the circuit breakers’ individual pole-interrupting capability."
• UL 489, ”Standard for Molded Case Circuit Breakers” includes singlepole, full-voltage test requirements for multiple-pole circuit breakers
– Test is at a relatively low current value
– Multiple-pole rating can be tested/listed to be higher than the standard
• Does not require a corresponding higher level single-pole test
– For example, a 100 A, 480 V, 3-pole circuit breaker is listed for 65 kA
• That is for line-to-line faults where 2- or 3-poles interrupt the fault
• The only required single-pole test at 480 V is 8,660 A
• MCC units with circuit breakers have not be listed for use with corner
grounded Delta power systems
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
20
Circuit Breakers -
Short Circuit Interrupting Ratings
• Dependent on voltage rating and number of circuit breaker poles
Typical Circuit Breakers Used In MCCs
CB
Type
Poles
LP
LP
Voltage Rating
120
120/240
240
277
480Y/277
480
600
1
-
10 kA
-
-
-
-
-
2,3
-
10 kA
-
-
-
-
-
PB
1
65 kA
-
-
14 kA
-
-
-
PB
2,3
-
-
65 kA
-
14 kA
-
-
MCC
1
-
-
-
65 kA
-
-
-
MCC
2,3
-
-
100 kA
-
-
65 kA
25 kA
– Lighting Panel (LP) circuit breakers
• Only have Slash Ratings
– Could be used with 208Y/120 V, solidly grounded Wye power system
– Could not be used with 240 V, ungrounded Delta power system
– Plug-In Panelboard (PB) branch circuit breakers
• Have Straight Ratings for 120, 240, 277 V, Slash Rating for 480Y/277 V
– Could be used with 240 V, ungrounded Delta power system
– Could not be used with 480V, ungrounded Delta power system
– Typical motor control center (MCC) unit circuit breakers
• Could be used on all power systems, except corner grounded Delta
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
21
Circuit Breakers –
Corner Grounded Delta Power Systems
• Circuit breakers not typically used
– Usually only tested per UL 489
minimum single-pole requirements
– Unless tested, must use 5 kA for MCC
unit interrupting/withstand rating
• Unit will not be UL 845 listed
• Phase-to-Phase fault interrupted by
two poles, fully tested to meet listed
rating
• Phase-to-ground fault requires a
single-pole of the circuit breaker to
interrupt the fault
– With full line-to-line voltage
– Short circuit current could equal
phase-to-phase short circuit current
– Very likely to exceed UL 489 minimum
single-pole requirements
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
22
Circuit Breakers –
Other Than Corner Grounded Delta Power Systems
• Single-pole interrupting ratings may need to be examined if the power
system is one of the following
– Ungrounded Wye
– Ungrounded Delta
– Impedance grounded Wye
• When a phase-to-ground fault occurs, the fault current will typically be
low enough that circuit breakers and fuses will not open
– Continuity of power is the advantage of these types of systems
• If the fault is not removed, and another phase-to-ground fault occurs, on
a different phase, a “phase-to-ground-to-phase” fault is created
– If ground path is low-impedance, this is essentially a phase-to-phase fault
– Depending on where the faults occur, the fault current may need to be interrupted by
a single-pole of one circuit breaker, with full line-to-line voltage across it.
• Similar to the phase-to-ground for a corner grounded Delta power system
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
23
Circuit Breakers –
Double Phase to Ground Fault
• Could involve a single-pole of one
circuit breaker
– Example 1: Fault F1 and F2 present
•
•
•
•
F1 through ground to F2
F2 through single-pole of MCB to L1
L1 through transformer to L2
L2 to F1
– One fault would need to be on bus
• Not likely for CENTERLINE bus design
• More likely a single-pole in two circuit
breakers
– Example 2: Fault F1 and F3 present
•
•
•
•
•
F1 through ground to F3
F3 through single-pole of FCB1 to MCB
Through single-pole of MCB to L1
L1 through transformer to L2
L2 to F1
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
24
Circuit Breakers –
Other Than Corner Grounded Delta Power Systems
• Can circuit breakers be used on power systems which are
– Ungrounded Wye?
– Ungrounded Delta?
– Impedance grounded Wye?
• Yes, an article released by NEMA Molded Case Circuit Breaker
manufacturers discussed the reasons that circuit breakers can be used
on these systems*
– Two faults would need to be present at the same time
• These power system types should use some means to detect ground faults
• Faults should be removed from service or corrected in a timely manner
• Occurrence of the second fault may trip overcurrent protective devices
– Negates the advantage of using these systems
– If fault is arcing, it is likely to cause a phase-to-phase fault, resulting in fault clearing
by multiple poles of one circuit breaker
– Fault path impedance is likely to be high, limiting the fault current
– A single-pole of another circuit breaker is likely to also be breaking the fault
• Typically then, there will be two circuit breaker poles breaking the fault
*Article entitled “Molded-Case Circuit Breaker-Individual Pole Interrupting Capacity”, IAEI News Magazine, May-June 2002
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
25
Fusible Switches
• Are suitable for use with all power system configurations
– Fuses are designed to individually interrupt their listed short circuit current at
voltages less than or equal to their voltage rating
– Note: Power systems which include a grounded phase conductor
• Cannot have fuses in the phase with the grounded conductor
– Design switch without fuse clips in the grounded phase
– Provide a dummy fuse in clips for the grounded phase
• Fuse selection criteria are
– Maximum voltage rating (250 V, 600 V)
– Short circuit interrupting rating (typically 100kA or higher)
– Fuse Class (CC, J, RK1, RK5, L , HRCII-C)
• Power system characteristics typically help determine voltage rating and
short circuit interrupting rating
– User preference determines selection of fuse class
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
26
Agenda
1. Introduction
2. Power System Configurations
3. Disconnecting Means
4. Unit Selection
5. Neutral Bus and Neutral Options
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
27
Unit Selection
• Proper selection needs to account for the characteristics of the power
system which will be used to feed power to the MCC
• Selections based on such characteristics as load rating, system voltage
and short circuit withstand or interrupting capacity are obvious.
• Other characteristics are important for proper unit selection
–
–
–
–
–
–
Is the power system Wye or Delta?
Is it grounded, ungrounded, or impedance grounded?
Is a neutral being brought to the MCC?
Are there any neutral loads?
Are there any neutral loads larger than 280A?
Is the MCC going to be the Service Entrance?
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
28
Main Incoming Unit Selection
• Three types of main incoming units are available
– Main lug only
– Fusible Switch
– Circuit Breaker
• Review of the discussion for “Disconnecting Means Selection”
• 4-wire systems may require that the main incoming unit have provisions
for the incoming neutral cables
– Horizontal neutral bus and related options may be required
• Solidly grounded Wye systems with rated 1000 A or more may require
ground fault protection
– Consult local codes for requirements
• Is the MCC going to be the Service Entrance?
– Consult local codes for requirements
– Quick delivery main circuit breakers and fusible switches meet NFPA 70 Service
Entrance requirements
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
29
Service Entrance –
Solidly Grounded Wye, No Neutral Loads
L1
MCC WITH SERVICE
ENTRANCE ONLY
TRANSFORMER
FEEDING POWER TO
MCC
L1
L2
MCB
L1
L2
L2
L3
L3
N
N
N
L3
MAIN BONDING
JUMPER
PROVIDED BY
AB AND
CONNECTED BY
OTHERS
G
NEUTRAL
CONNECTION
IN MCC
GROUND
CONNECTION IN
MCC (GROUND
BAR)
G
GROUNDING
ELECTRODE BY
OTHERS
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
30
Service Entrance –
Solidly Grounded Wye With Line-to-Neutral Loads
• May require horizontal neutral bus and other related options
MCC WITH SERVICE ENTRANCE
AND LINE TO NEUTRAL LOADS
INCOMING LINE UNIT
TRANSFORMER
FEEDING POWER TO
MCC
L1
L1
L2
FEEDER UNIT
MCB
FCB
L1
L2
L2
L3
L3
LOAD
LOAD
N
LOAD
L3
N
MAIN BONDING
JUMPER
PROVIDED BY
AB AND
CONNECTED BY
OTHERS
G
N
NEUTRAL
CONNECTION
IN MCC
GROUND
CONNECTION IN
MCC (GROUND
BAR)
G
GROUNDING
ELECTRODE BY
OTHERS
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
31
Not Service Entrance –
With Neutral, With or Without Line-to-Neutral Loads
• Neutral is grounded (bonded to ground) outside of MCC at upstream
service entrance
– Do not make connection between neutral and ground in this MCC
MCC WITH LINE TO NEUTRAL LOADS
ONLY (NO SERVICE ENTRANCE)
INCOMING LINE UNIT
TRANSFORMER
FEEDING POWER TO
MCC
L1
L1
L2
N
MCB
FEEDER UNIT
FCB
L1
L2
L2
L3
L3
N
N
LOAD
LOAD
GRD
LOAD
L3
Note: Grounded
at upstream
service
entrance
G
NEUTRAL
CONNECTION
IN MCC
GROUND
CONNECTION IN
MCC (GROUND
BAR)
G
GROUNDING
ELECTRODE BY
OTHERS
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
32
Metering Unit Selection
• Metering units should be selected which are compatible with the power
system being used
• Analog metering units
– 4-wire systems with line-to-neutral loads need to use units which will monitor line-toneutral voltages and neutral current
• Standard MCC analog metering units are designed for 3-wire systems
• Configurations for 4-wire systems can be supplied on the engineered delivery
program
• Digital metering units
– If the system is not a solidly grounded Wye, the metering unit should be examined
for maximum line-to-voltage rating
• Standard MCC metering units are limited to 347 V line-to-neutral
– e.g. ungrounded Delta, line-to-ground voltage may exceed 347 V
• Other configurations can be supplied on the engineered delivery program
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
33
Unit Selection
• Surge Suppressors
– Selected units which are compatible with the power system being used
– e.g. do not use a unit designed for Delta systems on a 4-wire Wye system, there will
be no phase-to-neutral protection or neutral-to-ground protection
• Feeders
– Review the discussion for “Disconnecting Means Selection”
• Full-voltage Starters
– Review the discussion for “Disconnecting Means Selection”
– If ground fault protection is selected, and an impedance grounded system is used,
check compatibility of the ground fault protection with the maximum ground fault
current
• e.g. if impedance limits current to 10 A, but the ground fault protection only
senses 20 A or higher, then the ground fault protection will never trip!
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
34
Unit Selection
• Variable Frequency Drive
– When used on systems other than solidly grounded Wye, units should be examined
for protective circuits referenced to ground. Most manufacturers will advise to
remove or isolate those circuits from ground
– Option code 14PSUG will do this for MCC mounted PowerFlex drive units
• Lighting Panel
– Power source needs to be provided/connected by user
– Review circuit breaker ratings to ensure compatibility with power system
– Circuit breakers in standard units are rated 120/240 V
• Plug-in Panelboard
–
–
–
–
Units on standard delivery program are fed from MCC bus
Review circuit breaker ratings to ensure compatibility with power system
Branch circuit breakers in standard units are rated 480Y/277 V
Panel neutral and ground bar are provided
• Quick delivery program, user must connect to system neutral and ground
• May need to include neutral connection plate in MCC structure
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
35
Unit Options
• Ground detection lights
– Available for power systems which are not solidly grounded
• With no ground faults, all three lights are dim
• With one ground fault present, one light is unlit, the other two are brighter
• Ground faults on solidly grounded systems typically will exhibit high fault
currents, protective device will trip, clearing the fault
• Ground fault protection for Main Fusible Switch
– Available on standard delivery program for 1600 A and 2000 A switches
– Available only for solidly grounded Wye power systems
• e.g. Do not use on impedance grounded systems. If impedance limits current
to 10 A, but the ground fault protection only trips at higher currents, then the
ground fault protection will never trip!
• Ground fault protection for Main Circuit Breaker
– Available on standard delivery program for 600 A frame and larger
– Available only for solidly grounded Wye power systems
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
36
Agenda
1. Introduction
2. Power System Configurations
3. Disconnecting Means
4. Unit Selection
5. Neutral Bus and Neutral Options
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
37
Neutral Bus and Neutral Options
• When a 4-wire power system is used, and the neutral is brought to the
MCC, additional data is needed
– Size and quantity of neutral cables
– Is neutral bus required?
• If so, half- or full-rated?
• All sections? or only where needed?
– Are line-to-neutral loads being served?
• If so, are any loads larger than 280 A?
• Loads up to 280 A are supported on the quick delivery program
– If a main fusible switch or circuit breaker is used, is it service entrance?
• These units are supplied with a main bonding jumper, for customer use if
service entrance
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
38
Horizontal Neutral Bus
•
•
•
•
Located on the same bus support as the horizontal power bus
Can be provided in all sections or up to four specified sections
Can be provided as half- or full-rated
Additional options are required to gain access to the neutral bus
– Main incoming unit requires incoming neutral bus option
– For sections with units serving line-to-neutral loads
• Vertical neutral bus is available
• Neutral connection plate is available
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
39
Horizontal Neutral Bus
Neutral Power Bus located
above 3 Phase Power Bus,
DeviceNet located below
Power Bus.
Neutral Power Bus located
below 3 Phase Power Bus,
DeviceNet located above
Power Bus.
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40
Neutral Bus Options –
Incoming neutral bus
• Provides a means to accommodate incoming neutral cables
• Factory connected to horizontal neutral bus
• Incoming neutral bus with Main Circuit Breaker or Switch
• Supplied with a main bonding jumper
– If service entrance ,user must connect bonding jumper to neutral assembly
• Meets NFPA 70 N.E.C. Service Entrance requirements
• If using main circuit breaker with ground fault protection, then neutral current
sensor will be factory installed in the incoming neutral bus assembly
• Available to match neutral bus rating, full or half
• Full rated, lugs match quantity of main device lugs
• Half rated, lugs match half the quantity of main device lugs
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
41
Neutral Bus Options –
Incoming neutral bus
MCB
MLO
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42
Neutral Bus Options -
Incoming Neutral Connection Plate
•
•
•
•
For main incoming units rated 400A or less
Not available with horizontal neutral bus
Provides a lower cost means to accommodate incoming neutral cables
Incoming neutral connection plate with Main Circuit Breaker or Switch
– Supplied with a main bonding jumper
• If service entrance, user must connect bonding jumper to neutral assy
– Meets NFPA 70 N.E.C. Service Entrance requirements
• Specifications
–
–
–
–
Rated 280 A
¼” x 2” x 12” bus bar
Installed on insulated standoffs
Provided with one, #6-250 kcmil lug
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
43
Neutral Bus Options -
Incoming Neutral Connection Plate
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44
Neutral Bus Options –
Vertical Neutral Bus
• Used for connecting neutral loads or line-to-neutral
control voltage
– Factory wired to line-to-neutral control circuits
• Copper with tin plating
– 200 A, 300 A, 600 A ratings available
•
•
•
•
Installed on insulated standoffs
Full length cover/guard provided
Requires 9“ (229 mm) vertical wire way
Requires horizontal neutral bus
– Factory connected to horizontal neutral bus
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
45
Neutral Bus Options –
Neutral Connection Plate
• Available in
– Top or bottom horizontal wireway
– 0.5 space factor unit space
• Horizontal neutral bus not supplied
– User is required to connect the plate to
the incoming neutral connection plate
• Horizontal neutral bus supplied
– Plate in top or bottom wireway will be
factory connected to neutral bus
• Specifications
–
–
–
–
Rated 280 A
¼” x 2” x 12” bus bar
Installed on insulated standoffs
Provided with one, #6-250 kcmil lug
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
46
Sources of Selection Information
• CENTERLINE 2100 MCC
configurators CIRCE and CenterONE
– Help prevent improper selections
– Have been updated to require additional
power system information
– CenterONE is available to anyone
http://www.ab.com/software/pcp/
• Additional product selection
information please refer to
– 2100-CA001x-EN-P “CENTERLINE 2100
Motor Control Center Catalog”
– 2100-AT003x-EN-P “Power System
Considerations for Product Selection”
• Specific component literature
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
47
Sources of Selection Information
• Specification Checklist for
CENTERLINE 2100 Motor Control
Centers, 2100-SR003x-EN-P
– Can be used to easily communicate
power system configurations to the
person who will configure the MCC
• Product Profile for
CENTERLINE 2100 MCCs
2100-PP020x-EN-P
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
48
Conclusion
• It is simply not enough to know that there is “three-phase power” coming
to the MCC
– Three phase conductors coming to the MCC does not give any information in regard
to how the power system is configured
– The presence of an equipment grounding conductor does not provide any indication
as to whether the power system is grounded
– Many MCC section and unit selections are dependent on the power system
configuration
A complete description of the power system
feeding an MCC is essential to help ensure
proper selection of MCC sections and units
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
49
Key Points / Summary / Call to Action
• Issues related to incorrect selections due to incomplete or incorrect
power system information can be costly to correct and delay project
schedules
• Do not guess on the value of available fault current
• Do not guess on type of the power system configuration
• Use the specification checklist to communicate the power system
information when requesting or providing MCC quotations
• Use the CenterONE MCC configurator to help ensure proper selections
are made
• If you have questions, don’t hesitate to contact your Rockwell Automation
or Distributor MCC Specialist
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.
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Copyright © 2008 Rockwell Automation, Inc. All rights reserved.