Copyright © 2008 Rockwell Automation, Inc. All rights reserved.

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.

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.

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.

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.

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.

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 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.

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.

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.

Delta Connected Power System Corner-grounded (Grounded “B” Phase)
3-wire only Grounding one phase stabilizes line-to-ground voltage at line-to-line voltage Less susceptible to voltage rises due to transients or other abnormal conditions Circuit breakers usually cannot be used Low interrupting ratings for full-voltage line-to-ground fault on a single-pole Typically not used for new installations Copyright © 2008 Rockwell Automation, Inc. All rights reserved.

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.

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-to-ground fault current Typically 10 A or less Reduces incident energy for line-to-ground 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.

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.

“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.

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.

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.

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.

Circuit Breakers – Single-pole Short Circuit Interrupting Rating
Article 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 single-pole, 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.

Circuit Breakers - Short Circuit Interrupting Ratings
Dependent on voltage rating and number of circuit breaker poles 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.

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.

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.

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 Copyright © 2008 Rockwell Automation, Inc. All rights reserved.

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.

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.

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.

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? Quick delivery main circuit breakers and fusible switches meet NFPA 70 Service Entrance requirements Copyright © 2008 Rockwell Automation, Inc. All rights reserved.

Service Entrance – Solidly Grounded Wye, No Neutral Loads
Copyright © 2008 Rockwell Automation, Inc. All rights reserved.

Service Entrance – Solidly Grounded Wye With Line-to-Neutral Loads
May require horizontal neutral bus and other related options Copyright © 2008 Rockwell Automation, Inc. All rights reserved.

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 Copyright © 2008 Rockwell Automation, Inc. All rights reserved.

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-to-neutral 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.

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 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.

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 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.

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 Copyright © 2008 Rockwell Automation, Inc. All rights reserved.

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.

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.

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. Copyright © 2008 Rockwell Automation, Inc. All rights reserved.

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.

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.

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.

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.

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 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.

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.

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.

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.

Copyright © 2008 Rockwell Automation, Inc. All rights reserved.

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