Integrated, Intelligent
Motor Control Centers
2
Integrated, Intelligent Motor Control Centers
Industry Overview
The 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 Progression
MCC 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
Integrated, Intelligent Motor Control Centers
3
Traditional 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 (PLC“s), 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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Integrated, Intelligent Motor Control Centers
Integrated, 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 today’s 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 preconfigured; 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.
Integrated, Intelligent Motor Control Centers
Built-in Communication
Network
5
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.
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
•
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.
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Integrated, Intelligent Motor Control Centers
Droplines behind barriers
or vertical wireway
Trunkline behind
barriers
Intelligent Motor Control
Components
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❑
❑
❑
❑
❑
❑
❑
❑
❑
❑
❑
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Individual network
ports accessible in
vertical wireway
To qualify as an intelligent MCC, every unit – even the “nonintelligent” 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
Integrated, Intelligent Motor Control Centers
7
•Protective 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.
MCC Monitoring Software
•
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.
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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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 user’s
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 engineer’s desk.
Integrated, Intelligent Motor Control Centers
System Design and Testing
9
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 jogging
•Short 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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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.
Integrated, Intelligent Motor Control Centers
11
Cost Comparison
How 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 postshipment 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 ¼” 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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Integrated, Intelligent Motor Control Centers
Case 1
Class II MCC with a Larger,
Advanced Function PLC I/O
Chassis
Case 2
Class II MCC with a Smaller,
Basic Function PLC I/O Chassis
Case 3
MCC with DeviceNet Cabling
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.
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.
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.
Integrated, Intelligent Motor Control Centers
13
Variable Size Analysis
Additional Assumptions
•
The process to determine comparative costs consists of: Assume
an initial line-up containing ten (10) size 1 full-voltage nonreversing 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
.
14
Integrated, Intelligent Motor Control Centers
Cost Analysis for DeviceNet MCC vs. MCC Interwired to a Larger, Advanced Function PLC I/O Chassis
$150,000
Smaller jump when
another section is added
$130,000
MCC List Price
$110,000
$90,000
$70,000
Class II I/O 2 Inputs/Unit
Class II I/O 3 Inputs/Unit
Large jump when
another PLC chassis
is added
$50,000
Class II I/O 4 Inputs/Unit
DeviceNet w/4 Inputs/Unit
$30,000
10
12
14
16
18
20
22
24
26
28
30 32
34
36
38
Total Number of FVNR Starter Units
40
42
44
46
48
50
Integrated, Intelligent Motor Control Centers
15
Cost Analysis for DeviceNet MCC vs. MCC Interwired to a Smaller, Basic Function PLC I/O Chassis
$170,000
$150,000
Smaller jump when
another section is added
MCC List Price
$130,000
$110,000
$90,000
$70,000
Class II I/O 2 Inputs/Unit
Class II I/O 3 Inputs/Unit
$50,000
Class II I/O 4 Inputs/Unit
Large jump when
another PLC chassis
is added
$30,000
10
12
14
16
18
20
22
24
26
28
30
32
34
DeviceNet w/4 Inputs in Unit
36
Total Number of FVNR Starter Units
38
40
42
44
46
48
50
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Integrated, Intelligent Motor Control Centers
Findings 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 Comparison
Additional 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, ¼” 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
Integrated, Intelligent Motor Control Centers
17
Price Comparison
MCC interwired to MCC interwired to
a larger, advanced a smaller, basic
function PLC I/O
function PLC I/O
chassis
chassis
Sections
MCC with
DeviceNet
$13,722
$13,722
$13,722
672
672
672
65,983
65,983
65,983
Network communication 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
72
108
144
10,561
11,218
--
--
--
8,000
$116,170
$123,395
$118,621
Main lug provision
Starter Units
Doors
Class II wiring
Network Cabling
Total List Price
Prices derived using published list prices
Total Price Comparison for Representative MCCs
$130,000
Communication
interface module,
power supply unit,
network cabling
Class II wiring
$120,000
$110,000
Total Price
$100,000
$90,000
PLC or Linking
Device unit
$80,000
$70,000
$60,000
Sections, splice
kits, Main lug,
starter units, doors
$50,000
$40,000
MCC Interwired to MCC Interwired to DeviceNet MCC
Large I/O Chassis Small I/O Chassis
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Integrated, Intelligent Motor Control Centers
Findings and Conclusions
The 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.
Summary
Integrated, 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.
Integrated, Intelligent Motor Control Centers
19
Appendix A
Case Study for Factory-interwired I/O Chassis
This white paper uses a factory-interwired MCC as the basis for
comparison to the DeviceNet MCC. Is this valid? Wouldn’t a fieldinterwired 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.
---------------------------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 1
Electrical contractor (panel shop) designs, assembles, and interwires
PLC chassis located in a separate programmable control cabinet to an
MCC.
Case 2
Electrical contractor (panel shop) interwires PLC chassis located in
an MCC.
Case 3
Motor control center manufacturer interwires PLC chassis located in
an MCC, making it a factory-interwired MCC.
20
Integrated, Intelligent Motor Control Centers
General 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 starter’s auxiliary contact received at the input module.
Services and Materials Provided
Each 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
Integrated, Intelligent Motor Control Centers
Case 1
MCC and Separate
Programmable Control Cabinet
Wired by Electrical Contractor
21
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.
22
Integrated, Intelligent Motor Control Centers
Case 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.
Integrated, Intelligent Motor Control Centers
Case 3
Programmable Controller in
MCC Wired and Tested by
MCC Manufacturer
23
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).
24
Integrated, Intelligent Motor Control Centers
Conclusion
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
$ 45, 692
$ 23, 484
$ 8,460
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
--
$ 71, 011
$ 74, 340
$ 81, 391
$ 116,703
$ 97,824
$ 89,851
TOTAL LABOR COSTS
Material Costs
TOTAL MATERIAL COSTS
TOTAL COSTS
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
Integrated, Intelligent Motor Control Centers
25
Appendix B
Sample Data Point Calculations for Variable Size
Cost Comparison Graphs
The 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
4 Inputs per Unit
3 Inputs per Unit
2 Inputs per Unit
# of
Units
# of
# of
Inputs Outputs
# of
# of
# of PLC
# of
Input Output
Chassis Sections
Modules Modules
PLC
Total
Unit
Total
Section
Total
Splice
Kit
Sub
Total
Door
Interwiring
Adder
Total
10
20
10
2
1
1
2
$11,157
$15,260
$3,352
0
0
$29,769
$2,977
$32,746
15
30
15
2
1
1
3
11,157
22,890
5,028
0
36
39,111
3,911
$43,022
20
40
20
3
2
1
4
14,762
30,520
6,704
157
72
52,215
5,222
$57,437
25
50
25
4
2
1
5
16,185
38,150
8,380
157
108
62,980
6,298
69,278
30
60
30
4
2
1
6
16,185
45,780
10,056
157
144
72,322
7,232
79,554
35
70
35
5
3
2
7
25,919
53,410
11,732
314
108
91,483
9,148
100,631
40
80
40
5
3
2
8
25,919
61,040
13,408
314
144
100,825
10,083
110,908
45
90
45
6
3
2
9
27,342
68,670
15,084
314
180
111,590
11,159
122,749
50
100
50
7
4
2
9
30,947
76,300
15,084
314
0
122,645
12,265
134,910
10
30
10
2
1
1
2
$11,157
$15,260
$3,352
0
0
$29,769
$2,977
$32,746
15
45
15
3
1
1
3
12,580
22,890
5,028
0
36
40,534
4,053
44,587
20
60
20
4
2
1
4
16,185
30,520
6,704
157
72
53,638
5,364
59,002
25
75
25
5
2
1
5
17,608
38,150
8,380
157
108
64,403
6,440
70,843
30
90
30
6
2
2
6
25,160
45,780
10,056
157
72
81,225
8,123
89,348
35
105
35
7
3
2
7
28,765
53,410
11,732
314
108
94,329
40
120
40
8
3
2
8
30,188
61,040
13,408
314
144
105,094
10,509
45
135
45
9
3
2
9
31,611
68,670
15,084
314
180
115,859
11,586 127,445
50
150
50
10
4
2
9
35,216
76,300
15,084
314
0
126,914
12,691 139,605
10
40
10
3
1
1
2
$12,580
$15,260
$3,352
0
0
$31,192
$3,119
$34,311
15
60
15
4
1
1
3
14,003
22,890
5,028
0
36
41,957
4,196
46,153
20
80
20
5
2
1
4
17,608
30,520
6,704
157
72
55,061
5,506
60,567
25
100
25
7
2
2
5
26,583
38,150
8,380
157
36
73,306
7,331
80,637
30
120
30
8
2
2
6
28,006
45,780
10,056
157
72
84,071
8,407
92,478
9,718 106,893
9,433 103,762
115,603
35
140
35
9
3
2
7
31,611
53,410
11,732
314
108
97,175
40
160
40
10
3
2
8
33,034
61,040
13,408
314
144
107,940
10,794
45
180
45
12
3
3
9
42,009
68,670
15,084
314
108
126,185
12,619 138,804
50
200
50
13
4
3
10
45,614
76,300
16,760
471
144
139,289
13,929 153,218
118,734
26
Integrated, Intelligent Motor Control Centers
MCC with Smaller, Basic Function PLC
4 Inputs per Unit
3 Inputs per Unit
2 Inputs per Unit
# of
Units
# of
# of
Inputs Outputs
# of
# of
# of PLC
# of
Input Output
Chassis Sections
Modules Modules
PLC
Total
Unit
Total
Section Splice
Total
Kit
Sub
Total
Door
Interwiring
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
MCC with DeviceNet
Module with 4 inputs in Unit
# of PLC
# of
# of Units Chassis Sections
PLC
Total
Unit Total Splice Kit
Door
Total
10
1
2
6,000
22,260
0
0
$33,612
15
1
3
6,000
33,390
0
36
$47,454
20
1
4
6,000
44,520
157
72
$61,453
25
1
5
6,000
55,650
157
108
$75,295
30
1
6
6,000
66,780
157
144
$89,137
35
1
7
6,000
77,910
314
180
$103,136
40
1
7
6,000
89,040
314
0
$114,086
45
1
8
6,000
100,170
314
36
$127,928
50
1
9
6,000
111,300
314
72
$141,770
Comparison of Total Costs
Total for MCC Interwired to Large I/O Total for MCC Interwired to Small I/O
Chassis
Chassis
# of Units
2 Inputs
3 Inputs
4 Inputs
2 Inputs
3 Inputs
DeviceNet
Total
4 Inputs
% Difference for MCC with
DeviceNet vs. MCC Interwired
to Large I/O Chassis
2 Inputs
% Difference for MCC with
DeviceNet vs. MCC Interwired
to Small I/O Chassis
3
4
2
Inputs Inputs Inputs
3
4 Inputs
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%
10.0%
-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 $104,411 $113,192 $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%
50 $134,910 $139,605 $153,218 $145,229 $160,324 $173,165 $141,770
5.1%
1.6%
-7.5%
Publication Number 2100-WP001A-EN-P — December 2000
0.8%
-9.1%
-16.7%
-2.4% -11.6%
-18.1%
Copyright © 2000 Rockwell Automation, Inc. All Rights Reserved.