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Integrated, Intelligent Motor Control Centers
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2 Integrated, Intelligent Motor Control CentersIndustry OverviewThe goals for any commercial or industrial process are simple: minimize overall costs and enhance productivity. To achieve these goals, processes require better monitoring, less downtime, and faster maintenance. Obtaining real-time process information requires integrating hardware, software, and communications. Communication and advanced sensing technologies now exist at the device level, and recent enhancements make a completely integrated solution both usable and affordable.
Motor control centers (MCCs) occupy a prominent role in control schemes, housing a comprehensive array of control and monitoring devices. MCCs have moved rapidly to include the latest component technologies and integrating these advanced technologies presents a major opportunity to transform islands of data into useful information that minimizes downtime. This paper focuses on technology integration methods in MCCs, and quantifying associated costs and benefits.
Historical ProgressionMCC Benefits The benefits of MCCs are well documented and proven by the
approximate $1.5 billion USD global market. These benefits include:
Quicker installation at a lower cost with its own power bus and factory-wired and tested units, field wiring and testing are minimized.
Saves floor space compared to individually mounting the same devices
Reduced planning and downtime - standardized sections and units simplify design and training; plug-in units can be easily replaced and rearranged
Expandability sections and units can be added to existing MCCs
Increased level of safety fault containment is part of MCC design, and units can be easily unplugged to service at a workbench, away from hazardous voltages
Faster delivery entire system arrives ready to install as a single entity, with no additional design or components to coordinate
Serviceable with power ON at adjacent starters the inherent isolation of MCC units makes it possible to work on a given unit without de-energizing any adjacent units, and still conform to code and OSHA requirements
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Integrated, Intelligent Motor Control Centers 3Traditional Electromechanical Components
Traditionally, MCCs contained only electromechanical components and all connections were hardwired. These components remain the workhorses even today, with over half of all MCC units containing only electromechanical devices.
Solid-State Components Advances in solid-state technology ushered in a revolution in control systems with intelligent devices that could be programmed to do more than just turn a motor on and off. These smart components found a warm reception in MCCs, and soon AC drives, soft starters, programmable logic controllers (PLCs), and electronic overload relays were standard offerings in MCC units. Integration was accomplished through hard wiring to an I/O Chassis.
For a detailed discussion of issues and costs associated with interwiring in MCCs, refer to Appendix A.
Networked Components The advent of device-level communication networks brought new possibilities for advanced monitoring, control, and diagnostics. These networks also greatly simplified wiring, eliminating the bundles of control interwiring and corresponding complex interwiring diagrams.
Although early MCC network communication brought benefits, there were also some challenges:
Reliability and flexibility shortcomings in the daisy chain drop-line architecture connecting units to the main trunk line. Adding new units or accidental breaks in the chain affected any downstream units in that connection, potentially shutting down equipment.
Safeguarding exposed trunk line and drop line cables in the wireways, when pulling and installing other power cables.
Establishing initial network communications with MCC unit devices.
Separating power and communication cables to meet code requirements. In confined wireways, adequate separation was difficult at best.
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4 Integrated, Intelligent Motor Control CentersIntegrated, Intelligent MCC The network communication challenges revealed a need to integrate the three major system components: the communications, the hardware, and the software.
These next generation, integrated, intelligent MCCs are current technology. The design streamlines installation, set-up, and changes; delivers real-time monitoring of the MCC; and easily integrates into a facility-wide network.
The questions for todays users are:
What is the extra cost to buy an integrated, intelligent MCC?
What are the real advantages and benefits for my facility vs. potential headaches and extra cost?
The following section highlights some issues that a user should consider.
Key Issues To Consider When Evaluating an Integrated, Intelligent MCC
Different Elements vs. a Standard MCC
An integrated, intelligent MCC will contain some different elements in both the sections and the units, plus software. These can be categorized as: the built-in communication media, intelligent motor control components, and MCC monitoring software. Keep in mind that an MCC may not be an integrated, intelligent MCC, just because it includes these elements. The early versions of MCCs with communication networks contained variations of these elements. The major distinction is that there was not a harmonized design that deliberately integrated the communication network, hardware, and software.
A standard MCC ships without interwiring, and requires extensive interwiring, documenting, and testing in the field. The integrated, intelligent MCC arrives ready to install, pre-tested and pre-configured; the communication cables are installed and tested, the intelligent devices are pre-programmed (with baud rate, node number, trip current, etc.), and the software screens are pre-configured.
The following sections review important considerations for the elements outlined above, and provide a framework for evaluating potential integrated, intelligent MCC offerings.
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Integrated, Intelligent Motor Control Centers 5Built-in CommunicationNetwork
The communication network needs to be analyzed with respect to both the network performance and the physical construction.
Proven, open communication network The trend toward open networks (as opposed to proprietary networks) is clear, and the advantages are well documented. So how do you choose an open network? The following criteria form a useful checklist. DeviceNet is evaluated as an example of an excellent open network choice.
Optimized Physical Construction The obvious approach for routing network cables in MCCs is through the horizontal and vertical wireways. Although this method has been successful, the opportunity exists for a more optimized solution.
Trunk lines and drop lines isolated behind barriers Avoids potential damage to communication cables during installation and maintenance activities.
Independent, easy-connect ports on drop lines The ideal configuration provides independent ports, readily accessible, to simplify installing, withdrawing, relocating, and adding plug-in units. This configuration replaces the daisy-chain architecture, where moving or adding an MCC unit required interrupting the chain and disabling downstream units.
Criteria DeviceNet
Throughput Up to 500 kbps communication rate
Cost per node Low node cost, due to high production volume of controller area network (CAN) chips
Immunity to typical MCC noise
Proven noise immunity (refer to Publication 1485-WP001A-US-P)
Cable rated for use adjacent to power wiring
Both flat and round Class 1, 8A, 600V cabling available
Accepted by a wide range of suppliers and users
DeviceNet products are offered by over 300 suppliers, with over half a million installed nodes
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6 Integrated, Intelligent Motor Control CentersIntelligent Motor ControlComponents
To qualify as an intelligent MCC, every unit even the non-intelligent ones - must have communication capability. This is necessary in order to replace the traditional control interwiring with a single communication wire. Ideally, all the units should also have input points to monitor devices like the disconnect switch, contactor, overload relay, or a hand-off-auto selector switch. A network scanner module or network linking device must also be provided to collect and distribute the device data in the MCC. An integrated, intelligent MCC should have at least the following components available.
Intelligent overload relays The most common device in the MCC is the motor starter, so overload relay intelligence is paramount. Users should expect:
Built-in network communication
Input points (for monitoring disconnect or selector switch)Output points (for controlling contactor)LEDs for status indication
Trunkline behind barriers
Droplines behind barriers or vertical wireway
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
Individual network ports accessible in vertical wireway
q
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Integrated, Intelligent Motor Control Centers 7Protective functions thermal overload, underload, jam, current imbalance, stall, phase loss, zero sequence ground fault, and PTC thermistor input.
Programmable parameters for the protective functions - trip level, warning level, time delay, and inhibit window. The ability to program these features avoids the nuisance trips that often led to users disabling protective functions. Warning alarms alert users to a potential trip, and allow actions to avert impending downtime. Time delays and inhibit windows allow recognition of abnormal current loads (e.g. extended starting times with high currents), without nuisance tripping.
Current Monitoring phase, average, full load, ground fault, imbalance percent, and percent thermal capacity used are important monitoring features.
Diagnostics device, warning, and trip status; time to overload trip; history of last five trips; time to reset.
Miniature I/O module for non-intelligent units Traditional electromechanical starters and feeder disconnects have no means to communicate with networks. Wiring to a distant I/O chassis is not the ideal solution. The preferable solution is an I/O module within the unit small enough so that the MCC unit size is not altered - to link the device and the network. The I/O module should have an adequate number of inputs and outputs, according to the unit functions. For a starter, four inputs and two outputs satisfy 99% of applications.
Network communication interface module with input points Intelligent devices often require an external communication module. Ideally, this module should contain input points (again, to eliminate wiring to a distant I/O chassis). Four inputs are sufficient for most applications.
MCC Monitoring Software Integrated, intelligent MCCs have dedicated software that delivers a window into the motor control center and related equipment. MCC software eliminates creating costly customized MCC screens within operator interface software, yielding a plug and play solution usable by computer novices. The following checklist identifies benchmarks for integrated, intelligent MCC software.
Operates in a familiar environment The software will be easiest to use if it behaves according to known operating environments, e.g. Windows.
Includes unique MCC documentation to initialize screens Every MCC is unique. The application program, upon installation, should access specific information to generate screens containing data pertinent to that MCC.
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8 Integrated, Intelligent Motor Control Centers Initiates network communication Establishing devices as recognized entities on a network can be the most time-consuming step. In the optimal situation, the MCC manufacturer downloads user-specific information like node addresses (per user specification or a standard scheme), and baud rate, then tests the entire system for accurate functions and communication. Upon installing the MCC and software, the user only needs to sit back and let the software poll the pre-configured devices to match the device information with the user database.
Displays pre-configured screens showing most common parameters Intelligent MCC software can access the users specific data files and build the corresponding screens. The following pre-configured software screens are useful:
MCC line-up (elevation) view Realistic dynamic display that shows unit type, nameplate information, and status of units.
Unit View Supplies dynamic information about the unit and network device. Parameters of greatest interest are already shown, and can be changed if necessary. Data can be displayed digitally, on meters or trend graphs.
Event Logging Automatically logs preset and user-defined faults and warnings, and accepts manual entries such as maintenance activities and equipment updates.
Spreadsheet View Ideal for viewing the most information at a glance. Sorting and filtering capabilities help users organize pertinent data.
Includes all user-specific documentation A comprehensive documentation database minimizes frustration and downtime experienced while trying to locate misplaced documentation. Valuable documentation components are:
Unit wiring diagrams
As-built drawings of the MCC line-up
Product user manuals
Spare parts list
Databases should allow users to add and change information, especially wiring diagrams.
Can be accessed at any network level The user should be able to view the MCC by plugging into any network level, such as DeviceNet, ControlNet, or Ethernet. This feature gives the user flexibility to locate the software on a maintenance laptop, in a control room, or at an engineers desk.
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Integrated, Intelligent Motor Control Centers 9System Design and Testing Component and systems tests should have been performed, with demonstrated compliance results readily available. The following tests assure that integrated, intelligent MCCs will function as expected and required.
Design verification tools - Designing networks requires a thorough understanding of the associated rules and parameters. A software design tool should be available to verify if critical network and design parameters have been met. Such software simplifies the entire design, order, and installation process.
Electrical and environmental testing - a full battery of tests, both individual components and when installed as a system include.
Noise immunity
IEEE qualification tests
Showering arc
Electric drill
Walkie-talkie
Overload joggingShort Circuit
UL component and cable qualification
Shock and vibration
Seismic
Completed system testing verify:
Cable system integrity
DeviceNet module communication
Network baud rate and node numbers
Software content
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10 Integrated, Intelligent Motor Control Centers Efficiently handles MCC changes and upgrades MCCs often have units added and rearranged, so the software must readily accommodate such data changes. The software should easily handle new units (with corresponding data information disks), and any location changes for existing units. Where users must supply information, step-through "wizards are the preferred method, since they guide the process.
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Integrated, Intelligent Motor Control Centers 11Cost ComparisonHow much extra does an integrated, intelligent MCC cost? The answer requires careful definition of MCC equipment to be compared in the cost analysis. For example, it is not logical to compare a standard unwired MCC to an integrated, intelligent MCC.
An appropriate analysis compares an MCC interwired with an I/O chassis, to an integrated, intelligent MCC. Both are complete interwired and tested systems, and both provide basic monitoring and control.
The study evaluates costs for three versions of MCCs: an MCC interwired to a larger, advanced function PLC I/O chassis; an MCC interwired to a smaller, basic function PLC I/O chassis; and an MCC with DeviceNet cabling and necessary DeviceNet hardware. Two versions of PLCs were used to account for size, function, and cost differences over a wide scope of PLC offerings. The study consists of two parts: a variable size analysis that compares costs as the number of units and sections increases (from 10 starters to 50 starters) with varying numbers of inputs; and a specific comparison of costs for a sample representative MCC line-up (eight sections). For simplicity, the variable size analysis includes one version of a full-voltage non-reversing (FVNR) starter unit added repeatedly. The sample representative MCC allows a check on the reasonableness of the variable size analysis, and is a more realistic representation of a typical MCC line-up.
General Assumptions for All Cases The study only includes actual manufacturer equipment and
wiring costs. Any charges associated with pre-order and post-shipment activities are assumed common and equal, and are excluded.
The study does not include costs for mechanical installation of MCCs.
Common costs for all three methods are not included, e.g. wiring diagrams, any engineering and drafting charges, network software, PLC programming software, and any dedicated equipment software. For the study, these costs are assumed to be common and equal.
Sections are 20 (508 mm) wide, 15 (381 mm) deep, NEMA Type 1, with 800 ampere copper main power bus with tin plating, and a x 1 horizontal ground bus.
FVNR starter units contain a circuit breaker disconnect with an internal normally open auxiliary contact; transformer control; red and green pilot lights; solid-state overload relay; and one normally open and one normally closed auxiliary contact mounted on the starter.
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12 Integrated, Intelligent Motor Control CentersCase 1 Class II MCC with a Larger, Advanced Function PLC I/O Chassis
Specific Case Assumptions
PLC unit has an eight-slot chassis, power supply, distributed I/O adapter module, and modules included for inputs and outputs. For the trend comparison, when the eight slots are exceeded, another PLC unit is added.
All inputs and outputs are isolated in accordance with transformer control in the units.
16-input and 16-output modules are included, reflecting typical user practices. For the trend comparison, when the 16 inputs or outputs are exceeded, an additional module is added.
Case 2 Class II MCC with a Smaller, Basic Function PLC I/O Chassis
Specific Case Assumptions
PLC unit has a seven-slot chassis, power supply, distributed I/O adapter module, and modules included for inputs and outputs. For the trend comparison, when the seven slots are exceeded, another PLC unit is added.
All inputs and outputs are isolated in accordance with transformer control in the units.
8-input and 8-output modules are included, reflecting typical user practices. For the trend comparison, when the eight inputs or outputs are exceeded, an additional module is added.
Case 3 MCC with DeviceNet Cabling
Specific Case Assumptions
DeviceNet cabling is 8 ampere, 600 Volt, Class 1, behind barriers, with connectors in the vertical wireway.
DeviceNet nodes are configured. Every FVNR starter unit contains a miniature I/O module with 4
inputs and 2 outputs. Linking device permits seamless communications from
ControlNet to DeviceNet. No PLC unit is required. 8 ampere DeviceNet power supply included.
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Integrated, Intelligent Motor Control Centers 13
Variable Size AnalysisAdditional Assumptions
The process to determine comparative costs consists of: Assume an initial line-up containing ten (10) size 1 full-voltage non-reversing starter units in sections, and a PLC unit to accommodate inputs and outputs. Add Size 1 FVNR starter units individually up to a total of 50. Include extra PLC units as required for inputs and outputs. Provide adequate sections to house all units.
Six (6) size 1 FVNR starter units per section. One output required for each coil. Three permutations were performed for the inputs, using two,
three, and four inputs. Inputs are typically used to monitor:Contactor
Overload relay
Unit disconnect switch
Hand-off-auto selector switch
The following graphs illustrate the comparative costs for DeviceNet and Class II MCCs as the number of FVNR starter units increases. The three Class II lines on each graph correspond to varying numbers of inputs. Refer to Appendix B for sample data point calculations used to produce the graphs.
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14 Integrated, Intelligent Motor Control CentersCost Analysis for DeviceNet MCC vs. MCC Interwired to a Larger, Advanced Function PLC I/O Chassis
$30,000
$50,000
$70,000
$90,000
$110,000
$130,000
$150,000
10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
Total Number of FVNR Starter Units
MCC
Lis
t Pric
e
Class II I/O 2 Inputs/Unit
Class II I/O 3 Inputs/Unit
Class II I/O 4 Inputs/Unit
DeviceNet w/4 Inputs/Unit
Smaller jump whenanother section is added
Large jump whenanother PLC chassisis added
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Integrated, Intelligent Motor Control Centers 15$30,000
$50,000
$70,000
$90,000
$110,000
$130,000
$150,000
$170,000
10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50Total Number of FVNR Starter Units
MCC
Li
st P
rice
Class II I/O 2 Inputs/UnitClass II I/O 3 Inputs/UnitClass II I/O 4 Inputs/UnitDeviceNet w/4 Inputs in Unit
Cost Analysis for DeviceNet MCC vs. MCC Interwired to a Smaller, Basic Function PLC I/O Chassis
Smaller jump whenanother section is added
Large jump whenanother PLC chassisis added
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16 Integrated, Intelligent Motor Control CentersFindings and Conclusions The DeviceNet MCC cost is nearly identical to a motor control
center interwired with an I/O chassis. The choice, therefore should be based on technology preference, not price.
As expected, the networked solution becomes more cost effective as the amount of information returned per MCC unit (i.e. number of inputs) increases.
Representative MCC ComparisonAdditional Assumptions All details listed under both the General Assumptions and the
Specific Case Assumptions apply.
MCC line-up includes eight NEMA Type 1 sections, with 800 ampere tin-plated copper main power bus, x 1 horizontal ground bus, two power bus splice kits, two ground bus splice kits
FVNR starter unit quantities and sizes:
(10) Size 1(9) Size 2(7) Size 3(4) Size 4(1) Size 5
Lug provision included for main incoming lines, rated 800A
Starter units have three inputs (3I), one output (1O) Total Inputs 93
Total Outputs 31
Larger, advanced function PLC requires two I/O chassis
Smaller, basic function PLC requires three I/O chassis
MCC with DeviceNet contains a unit with a DeviceNet to ControlNet linking device and one 8 ampere DeviceNet power supply unit
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Integrated, Intelligent Motor Control Centers 17Price ComparisonMCC interwired to a larger, advanced function PLC I/O
chassis
MCC interwired to a smaller, basic function PLC I/O
chassisMCC with DeviceNet
Sections $13,722 $13,722 $13,722
Main lug provision 672 672 672
Starter Units 65,983 65,983 65,983
Network communica-tion interface module in each starter unit
- - - - 21,700
Power supply unit - - - - 2,400
PLC unit of linking device unit
25,160 31,692 6,000
Doors 72 108 144
Class II wiring 10,561 11,218 - -
Network Cabling - - - - 8,000
Total List Price $116,170 $123,395 $118,621
Prices derived using published list prices
Total Price Comparison for Representative MCCs
$40,000
$50,000
$60,000
$70,000
$80,000
$90,000
$100,000
$110,000
$120,000
$130,000
MCC Interwired toLarge I/O Chassis
MCC Interwired toSmall I/O Chassis
DeviceNet MCC
Tota
l Pric
e
Communicationinterface module,power supply unit,network cablingClass II wiring
PLC or LinkingDevice unit
Sections, splicekits, Main lug,starter units, doors
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18 Integrated, Intelligent Motor Control CentersFindings and ConclusionsThe DeviceNet MCC price falls nearly at the midpoint between the two versions of motor control centers interwired with I/O chassis. The cost relationships correspond closely to the previous variable size analysis results.
SummaryIntegrated, intelligent MCCs substantially simplify wiring, troubleshooting, rearranging units, and adding sections and units. They also provide new information that can be used to minimize downtime, facilitate monitoring of MCCs and related equipment, and decrease repair time.With the diminishing cost of intelligence, they should be strongly considered for all applications.
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Integrated, Intelligent Motor Control Centers 19Appendix ACase Study for Factory-interwired I/O ChassisThis white paper uses a factory-interwired MCC as the basis for comparison to the DeviceNet MCC. Is this valid? Wouldnt a field-interwired MCC be a better basis? The factory-interwired pricing was chosen because it is lower than the price for field interwiring. A previous white paper documented the price comparisons. An excerpt follows.
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Since 1980, more than 50,000 sections of MCCs have been interwired to PLCs. The old concern about packaging logic devices in proximity to high voltage has been sufficiently laid to rest by the overwhelming success of these installations.
The question still surfaces as to who can interwire MCC units to the PLC modules most cost-effectively: the MCC manufacturer or a local contractor/panel shop. A major engineering construction firm wanted to determine the answer, and conducted an independent study that evaluated costs of interwiring PLC I/O chassis to motor control center units. Their study compared costs for both an MCC manufacturer and an electrical contractor to do the interwiring.
The comprehensive study was based on an actual user order that needed an MCC and PLC chassis with 320 I/O points, to control a manufacturing process with 25 motors. The study focused on three methods for interwiring the motor control center and PLC chassis, and reviewed costs to supply engineering, design, and construction necessary to provide, install, and make the equipment operational. The three methods were:
Case 1Electrical contractor (panel shop) designs, assembles, and interwires PLC chassis located in a separate programmable control cabinet to an MCC.
Case 2Electrical contractor (panel shop) interwires PLC chassis located in an MCC.
Case 3Motor control center manufacturer interwires PLC chassis located in an MCC, making it a factory-interwired MCC.
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20 Integrated, Intelligent Motor Control CentersGeneral Assumptions for All Cases
PLC I/O modules included for 160 inputs and 160 outputs.
All I/O are wired from PLC chassis to terminal blocks total of 640 wires, 1280 terminations.
25 output points are wired from the terminal blocks to motor starter coils total of 50 wires, 100 terminations.
25 input points are wired from the terminal blocks to motor starter auxiliary contacts total of 50 wires, 100 terminations.
Remaining 270 I/O (135 inputs, 135 outputs) are for field devices and are located in the MCC for convenience.
Terminations are pressure-plate type and do not require wire lugs.
PLC cabinet or MCC sections sized for four I/O chassis (three are purchased, one future space).
Hardwired emergency-stop relays and control relays (total of 24) are wired to terminals, and are located in a dedicated MCC compartment.
Internal MCC interlock wiring consists of 48 interlocks (two per relay) total of 96 wires, 192 terminations.
Completion criteria for I/O wired to starters: Each PLC output shall be energized, the unit control circuit tested, and feedback from the starters auxiliary contact received at the input module.
Services and Materials ProvidedEach case included estimates for engineering, drafting, materials, and installation. Specific case descriptions are identified below.
The following services and materials were provided by others and are common to all three cases. They are not included in the cost analyses:
Engineering
MCC single-line diagram and MCC arrangement
I/O assignments to load and inputs
Elementary wiring (schematic) diagrams for I/O and hardwired emergency stop and control circuits
Material and Construction Costs
MCC incoming power
PLC programming software
Wiring from field devices and motors to MCC and PLC I/O terminals
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Integrated, Intelligent Motor Control Centers 21Case 1 MCC and Separate Programmable Control Cabinet Wired by Electrical Contractor
Specific Case Assumptions The PLC I/O chassis and I/O terminals are located in a separate,
freestanding NEMA 12 cabinet designed specifically for the system (to include three I/O chassis with 320 digital I/O).
The PLC cabinet is located 10 feet (3 m) from the MCC (requires 20 feet [6.1 m] of conduit, 30 feet [9.1 m] of wire).
Interconnecting wiring between the PLC and MCC will be #14 AWG THHW / THWN copper wire routed in rigid galvanized steel conduit.
Five 2-inch (50.8 mm) conduits with (128) #14 AWG wires each, will be routed between the MCC and PLC cabinet.
Electrical contractor to wire I/O card wiring arms to the terminal strips.
Engineering Deliverables PLC cabinet layout drawing with bill of material.
Plan drawing showing location of MCC and PLC cabinet, and conduit routing.
Interconnection wiring diagram showing wiring between PLC and MCC.
Specify and purchase MCC.
Specify and purchase labor and materials for interwiring between the PLC cabinet and MCC units.
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22 Integrated, Intelligent Motor Control CentersCase 2 Programmable Controller in MCC Wired by Electrical Contractor
Specific Case Assumptions
The assumptions are identical to Case 1, except:
The PLC I/O chassis and I/O terminals are located in dedicated sections in the MCC.
I/O card wiring arms are wired to terminal strips by the MCC vendor.
Engineering Deliverables
Specify and purchase MCC that includes I/O chassis, terminal blocks, and relays.
Specify and purchase labor and materials for interwiring between the PLC section and MCC units.
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Integrated, Intelligent Motor Control Centers 23Case 3 Programmable Controller in MCC Wired and Tested by MCC Manufacturer
Specific Case Assumptions
The assumptions are identical to Case 2, except:
MCC manufacturer makes all interconnections between the PLC I/O chassis and MCC (facotry interwired MCC).
Engineering Deliverables
Specify and purchase MCC that includes I/O chassis, terminal blocks, relays, and all interwiring (factory interwired MCC).
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24 Integrated, Intelligent Motor Control CentersConclusion This independent study shows that Case 3 has the lowest interwiring cost- i.e. where the MCC manufacturer mounts and wires I/O in the MCC (factory interwired motor control center).
The study data, combined with other factory interwired advantages - like reduced start-up time, high quality wiring, and high quality documentation - support the trend toward increased purchases of factory interwired motor control centers.
Cost Breakdown - Case Study
Case 1 Case 2 Case 3
Labor Costs
Physical Design of PLC Cabinet and Control Room $ 5250 - - - -
2 AutoCAD Drawings-Panel Layout, COntrol Room 2500 - - - -
Elec. Design of PLC Cabinet and Interconnection 5000 $ 5000 - -
Interdiscipline Coordination, Quality, Management, Drawing Review 2500 2500 - -
2 AutoCAD Drawings-Interconnection, Wiring 1680 1080 $ 840
Management, Scheduling, Meetings 1680 1680 1260
RFQ Creation/Analysis 2820 1440 1440
Assembly & Installation of P:LC Cabinet (incl. wiring to terminal blocks) 6284 - - - -
Inspection(s) and Travel Expense 3920 1960 1960
Mechanical Installation of MCC 1500 2000 2000
Wiring Between MCC and PLC, Checkout 9570 4836 - -
Relay Interlock Wiring 588 588 - -
Field Start-Up Assistance 2400 2400 960
TOTAL LABOR COSTS $ 45, 692 $ 23, 484 $ 8,460
Material Costs
Motor Control Center 44436 73992 81391
Enclosure, PLC Components, Terminal Blocks, Panduit, Etc. 24797 - - - -
Relays for Safety Interlock 72 72 - -
Wiring (and conduit) Between MCC and PLC 1706 276 - -
TOTAL MATERIAL COSTS $ 71, 011 $ 74, 340 $ 81, 391
TOTAL COSTS $ 116,703 $ 97,824 $ 89,851
Rockwell Automation provided prices for:Case 1 MCC and PLC component
Case 2 MCC with PLC (PLC price included in MCC price)Case 3 MCC with PLC in MCC wired and tested
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Integrated, Intelligent Motor Control Centers 25
6
2
7
8
4
1
8
9
0
6
72382355
137783448Appendix BSample Data Point Calculations for Variable Size Cost Comparison GraphsThe tables show data points used to generate the graphs found in the Variable Size Cost Comparison section. All prices were derived using published list prices.
Details about FVNR units, input and output modules, PLC units, sections, splice kits, and doors are included in the General Assumptions and Specific Case Assumptions on pages 10-12.
MCC with Larger, Advanced Function PLC
# of Units
# of Inputs
# of Outputs
# of Input
Modules
# of Output
Modules
# of PLC Chassis
# of Sections
PLC Total
Unit Total
Section Total
Splice Kit
Door Sub Total
Inter-wiring Adder
Total
10 20 10 2 1 1 2 $11,157 $15,260 $3,352 0 0 $29,769 $2,977 $32,74
15 30 15 2 1 1 3 11,157 22,890 5,028 0 36 39,111 3,911 $43,02
20 40 20 3 2 1 4 14,762 30,520 6,704 157 72 52,215 5,222 $57,43
25 50 25 4 2 1 5 16,185 38,150 8,380 157 108 62,980 6,298 69,27
30 60 30 4 2 1 6 16,185 45,780 10,056 157 144 72,322 7,232 79,55
35 70 35 5 3 2 7 25,919 53,410 11,732 314 108 91,483 9,148 100,63
40 80 40 5 3 2 8 25,919 61,040 13,408 314 144 100,825 10,083 110,90
45 90 45 6 3 2 9 27,342 68,670 15,084 314 180 111,590 11,159 122,74
50 100 50 7 4 2 9 30,947 76,300 15,084 314 0 122,645 12,265 134,91
10 30 10 2 1 1 2 $11,157 $15,260 $3,352 0 0 $29,769 $2,977 $32,74
15 45 15 3 1 1 3 12,580 22,890 5,028 0 36 40,534 4,053 44,5820 60 20 4 2 1 4 16,185 30,520 6,704 157 72 53,638 5,364 59,0025 75 25 5 2 1 5 17,608 38,150 8,380 157 108 64,403 6,440 70,8430 90 30 6 2 2 6 25,160 45,780 10,056 157 72 81,225 8,123 89,3435 105 35 7 3 2 7 28,765 53,410 11,732 314 108 94,329 9,433 103,7640 120 40 8 3 2 8 30,188 61,040 13,408 314 144 105,094 10,509 115,6045 135 45 9 3 2 9 31,611 68,670 15,084 314 180 115,859 11,586 127,44
50 150 50 10 4 2 9 35,216 76,300 15,084 314 0 126,914 12,691 139,60
10 40 10 3 1 1 2 $12,580 $15,260 $3,352 0 0 $31,192 $3,119 $34,3115 60 15 4 1 1 3 14,003 22,890 5,028 0 36 41,957 4,196 46,1520 80 20 5 2 1 4 17,608 30,520 6,704 157 72 55,061 5,506 60,5625 100 25 7 2 2 5 26,583 38,150 8,380 157 36 73,306 7,331 80,6330 120 30 8 2 2 6 28,006 45,780 10,056 157 72 84,071 8,407 92,4735 140 35 9 3 2 7 31,611 53,410 11,732 314 108 97,175 9,718 106,8940 160 40 10 3 2 8 33,034 61,040 13,408 314 144 107,940 10,794 118,7345 180 45 12 3 3 9 42,009 68,670 15,084 314 108 126,185 12,619 138,8050 200 50 13 4 3 10 45,614 76,300 16,760 471 144 139,289 13,929 153,21
3 In
puts
per
Uni
t4
Inpu
ts p
er U
nit
2 In
puts
per
Uni
t
-
26 Integrated, Intelligent Motor Control CentersMCC with Smaller, Basic Function PLC
# of Units
# of Inputs
# of Outputs
# of Input
Modules
# of Output
Modules
# of PLC Chassis
# of Sections
PLC Total
Unit Total
Section Total
Splice Kit
Door Sub Total
Inter-wiring Adder
Total
10 20 10 3 2 1 2 $9,991 $15,260 $3,352 0 36 $28,639 $2,864 $31,503
15 30 15 4 2 1 3 10,982 22,890 5,028 0 72 38,972 3,897 42,869
20 40 20 5 3 2 4 18,364 30,520 6,704 157 72 55,817 5,582 61,399
25 50 25 7 4 2 5 20,973 38,150 8,380 157 108 67,768 6,777 74,545
30 60 30 8 4 2 6 21,964 45,780 10,056 157 144 78,101 7,810 85,911
35 70 35 9 5 3 7 29,346 53,410 11,732 314 144 94,946 9,495 104,441
40 80 40 10 5 3 8 30,337 61,040 13,408 314 180 105,279 10,528 115,807
45 90 45 12 6 3 8 32,946 68,670 13,408 314 0 115,338 11,534 126,872
50 100 50 13 7 4 9 40,328 76,300 15,084 314 0 132,026 13,203 145,229
10 30 10 4 2 1 2 $10,982 $15,260 $3,352 0 36 $29,630 $2,963 $32,593
15 45 15 6 2 2 3 18,728 22,890 5,028 0 36 46,682 4,668 51,350
20 60 20 8 3 2 4 21,337 30,520 6,704 157 72 58,790 5,879 64,669
25 75 25 10 4 3 5 29,710 38,150 8,380 157 72 76,469 7,647 84,116
30 90 30 12 4 3 6 31,692 45,780 10,056 157 108 87,793 8,779 96,572
35 105 35 14 5 4 7 40,065 53,410 11,732 314 108 105,629 10,563 116,192
40 120 40 15 5 4 8 41,056 61,040 13,408 314 144 115,962 11,596 127,558
45 135 45 17 6 4 9 43,665 68,670 15,084 314 180 127,913 12,791 140,704
50 150 50 19 7 5 10 52,038 76,300 16,760 471 180 145,749 14,575 160,324
10 40 10 5 2 2 2 $17,737 $15,260 $3,352 0 0 $36,349 $3,635 $39,984
15 60 15 8 2 2 3 20,710 22,890 5,028 0 36 48,664 4,866 53,530
20 80 20 10 3 3 4 29,083 30,520 6,704 157 36 66,500 6,650 73,150
25 100 25 13 4 3 5 32,683 38,150 8,380 157 72 79,442 7,944 87,386
30 120 30 15 4 4 6 40,429 45,780 10,056 157 72 96,494 9,649 106,143
35 140 35 18 5 4 7 44,029 53,410 11,732 314 108 109,593 10,959 120,552
40 160 40 20 5 5 8 51,775 61,040 13,408 314 108 126,645 12,665 139,310
45 180 45 23 6 5 9 55,375 68,670 15,084 314 144 139,587 13,959 153,546
50 200 50 25 7 6 10 63,748 76,300 16,760 471 144 157,423 15,742 173,165
2 In
puts
per
Uni
t3
Inpu
ts p
er U
nit
4 In
puts
per
Uni
t
-
MCC with DeviceNet
Comparison of Total Costs
# of Units
# of PLC Chassis
# of Sections
PLC Total
Unit Total
Section Total
Splice Kit
Door Total
10 1 2 $6,000 $22,260 $5,352 0 0 $33,612
15 1 3 6,000 33,390 8,028 0 36 47,454
20 1 4 6,000 44,520 10,704 157 72 61,453
25 1 5 6,000 55,650 13,380 157 108 75,295
30 1 6 6,000 66,780 16,056 157 144 89,137
35 1 7 6,000 77,910 18,732 314 180 103,136
40 1 7 6,000 89,040 18,732 314 0 114,086
45 1 8 6,000 100,170 21,408 314 36 127,928
50 1 9 6,000 111,300 24,084 314 72 141,770
Total for MCC interwired to Large I/O Chassis
Total for MCC interwired to Small I/O Chassis
% Difference for MCC with DeviceNet / MCC
interwired to Large I/O Chassis
% Difference for MCC with DeviceNet / MCC
interwired to Small I/O Chassis
# of Units
2 Inputs 3 Inputs 4 Inputs 2 Inputs 3 Inputs 4 InputsDeviceNet
Total 2 Inputs 3 Inputs 4 Inputs 2 Inputs 3 Inputs 4 Inputs
10 $32,746 $32,746 $34,311 $31,503 $32,593 $39,984 $33,612 2.6% 2.6% -2.0% 6.7% 3.1% -15.9%
15 43,022 44,587 46,153 42,869 51,350 53,530 47,454 10.3% 6.4% 2.8% 10.7% -7.6% -11.4%
20 57,437 59,002 60,567 61,399 64,669 73,150 61,453 7.0% 4.2% 1.5% 0.1% -5.0% -16.0%
25 69,278 70,843 80,637 74,545 84,116 87,386 75,295 8.7% 6.3% -6.6% 1.0% -10.5% -13.8%
30 79,554 89,348 92,478 85,911 96,572 106,143 89,137 12.0% -0.2% -3.6% 3.8% -7.7% -16.0%
35 100,631 103,762 106,893 104,441 116,192 120,552 103,136 2.5% -0.6% -3.5% -1.2% -11.2% -14.4%
40 110,908 115,603 118,734 115,807 127,558 139,310 114,086 2.9% -1.3% -3.9% -1.5% -10.6% -18.1%
45 122,749 127,445 138,804 126,872 140,704 153,546 127,928 4.2% 0.4% -7.8% 0.8% -9.1% -16.7%
50 134,910 139,605 153,218 145,229 160,324 173,165 141,770 5.1% 1.6% -7.5% -2.4% -11.6% -18.1%
Mod
ule
with
4 in
puts
in U
nit
2000 Rockwell International. All Rights Reserved. Printed in USAPublication 2100-WP001A-EN-P - December 2000
