Understanding intelligent motor control centers

Lately, there has been a lot of interest in the use of "intelligent" motor control centers (MCCs). But defining intelligence is not as easy as it sounds. To answer the question of intelligence, first take a look at traditional MCC technology.

02/15/2002


Key concepts
Motor control centers are like filing cabinets containing combination starters, lighting contactors, and other electrical distribution and control products.
Loads can be the source of important process or machine diagnostic information.
When specifying intelligent MCCs, consider cost, capability, and complexity.
Sections:
Fundamentals
Intelligent motor control systems
Cost-saving options
Smart decisions


Lately, there has been a lot of interest in the use of "intelligent" motor control centers (MCCs). But defining intelligence is not as easy as it sounds. To answer the question of intelligence, first take a look at traditional MCC technology.

Fundamentals

The role of a basic MCC is to provide a compact, modular grouping for motor control and electrical distribution components (Fig. 1). Think of an MCC as a filing cabinet, with drawers full of combination starters, lighting contactors, and other electrical distribution and control products. Historically, MCC units were electromechanical, with basic functions that included a power switching device, short-circuit and overload protection, local and remote actuation, and controller state indication.

There are a number of reasons for MCC popularity:

  • MCCs provide a single source for coordination of components. Electrical distribution and motor control equipment can be purchased as a pre-assembled, pre-tested system—usually at a less expensive installed cost when compared to separately mounted controls.

  • MCCs require significantly less line-side power wiring than separate controls, which makes them easier to install.

  • MCCs come in space-efficient packaging, with excellent configuration flexibility. They also centralize maintenance.

  • MCCs offer excellent fault containment and electrical component isolation.


    • MCCs are used in applications where there are multiple, remotely controlled loads linked to a central control point. In industrial plant applications, the central control point is usually an environmental control system, with HVAC, pump, and fan loads. Industrial process applications include many load types, such as conveyors, pumps, fans, and mixers. These loads often require coordinated control and can be the source of important process or machine diagnostic information. Distributed control systems (DCSs) or PLCs normally are used to provide this control and data acquisition functionality.

      Intelligent motor control systems

      Use of open networks, distributed I/Os, and electronic components is one way of defining an MCC as intelligent. Typically, intelligent systems have three things in common:

      • Control is achieved through a microprocessor-based system

      • Network technology is used to replace hardwiring

      • Some degree of enhanced diagnostic or protective functionality is included.

        • While many associate these technologies with intelligence, another definition has nothing to do with the technology involved. In today's competitive business environment, perhaps the definition of an intelligent MCC should be as simple as a unit that provides equivalent or greater functionality more economically. In other words, an intelligent MCC is simply an MCC that maximizes the value of the components in a given application.

          But how does one determine maximum value? Is it based on the cost of the equipment? That definition doesn't take into account the total cost of the unit. In other words, the cost to design, specify, purchase, install, commission, operate, maintain, and upgrade an MCC are all calculated into the total cost of ownership.

          Each individual in the chain is likely to define intelligence related to his or her perception of value. For example, consultants who design and specify equipment are interested in the reliability and performance of the components. A contractor may be primarily concerned with installed cost. A facility manager is likely to be worried about ease of operation and maintenance costs. And operations personnel are focused on the functionality and durability of the entire system. In other words, regardless of a person's function, a truly intelligent MCC will optimize the value of the equipment specific to that function.

          Cost-saving options

          There are several ways in which MCCs can be made more cost-effective.

          Bit-level networks to replace traditional hardwiring

          MCCs in this category are characterized by simplicity. They will almost always deliver the lowest installed cost. They allow localization of failures to improve maintenance and usually provide some additional functionality not economically feasible with hardwired systems.

          Installation and commissioning time is significantly improved over traditional MCCs. They do not require extensive system configuration or parameter management and can be maintained by most electricians. Concurrent engineering also is greatly facilitated.

          Bridges are available to most bit-level or byte-level networks and configuration is straightforward (an entire MCC is typically represented as one node). Computational resource and network bandwidth requirements are low.

          These systems are easily retrofitted to existing installations and do not require "intelligent devices" to provide benefits.

          Distributed I/Os

          Locating distributed I/O within each MCC (preferably within each shipping split) reduces installation and commissioning time for a lower installed cost. Construction is common across applications and provides clear segregation between automation and motor control. This segregation can be important where division of responsibilities, existing spares, and training are overriding issues.

          Processors can be added to most distributed I/O systems to provide local control capabilities. Integration into PLC-based control schemes is straightforward and distributed I/O is available for all popular networks.

          Intelligent devices

          Intelligent devices imbedded in the MCC not only provide network communications, but extensive functionality not available on standard devices, such as network configuration, diagnostics, extensive process information, and advanced protection for each unit.

          Significant technical expertise is required, but the systems have excellent life-cycle benefits in process applications where the additional information, diagnostics, and protective features easily justify the incremental cost of the equipment.

          Smart decisions

          Specification of intelligent MCCs requires taking into consideration the variables of cost, capability, and complexity. Therefore, it is important to realistically assess your capabilities and objectives. Keep in mind that additional functionality usually comes with additional cost or complexity that you may not need.

          The following list is a sampling of questions to consider when selecting and specifying intelligent MCCs.

          • Will I maximize my return on investment by lowering the installed cost of the MCC equipment or by providing significant additional functionality?

          • Will last minute changes be likely?

          • Is future expansion or modification likely?

          • How valuable is a reduction in installation and commissioning time?

          • Can the equipment be integrated into my overall control and information architecture?

          • Does my control system or network have enough capacity to handle the data provided?

          • Do I have a technical staff capable of maintaining the system?

          • What are the cabling and connection requirements of the system?

            • A good MCC supplier will offer a range of options; one size does not fit all. The manufacturer should be able to help you answer these questions, so you can select the best approach for your application. The supplier also should be able to integrate with multiple networks and existing control systems. They must be willing to work with third parties and value-added system integrators. And they should be able to provide total solution packages where appropriate. Finally, a complete functional test of the equipment prior to shipment is essential to realizing reductions in commissioning time. Be sure the vendor intends to conduct the test by actually energizing the I/O, not with simple point-to-point wiring checks.

               



The Top Plant program honors outstanding manufacturing facilities in North America. View the 2015 Top Plant.
The Product of the Year program recognizes products newly released in the manufacturing industries.
Each year, a panel of Control Engineering and Plant Engineering editors and industry expert judges select the System Integrator of the Year Award winners in three categories.
Doubling down on digital manufacturing; Data driving predictive maintenance; Electric motors and generators; Rewarding operational improvement
2017 Lubrication Guide; Software tools; Microgrids and energy strategies; Use robots effectively
Prescriptive maintenance; Hannover Messe 2017 recap; Reduce welding errors
The cloud, mobility, and remote operations; SCADA and contextual mobility; Custom UPS empowering a secure pipeline
Infrastructure for natural gas expansion; Artificial lift methods; Disruptive technology and fugitive gas emissions
Mobility as the means to offshore innovation; Preventing another Deepwater Horizon; ROVs as subsea robots; SCADA and the radio spectrum
Research team developing Tesla coil designs; Implementing wireless process sensing
Commissioning electrical systems; Designing emergency and standby generator systems; Paralleling switchgear generator systems
Natural gas engines; New applications for fuel cells; Large engines become more efficient; Extending boiler life

Annual Salary Survey

Before the calendar turned, 2016 already had the makings of a pivotal year for manufacturing, and for the world.

There were the big events for the year, including the United States as Partner Country at Hannover Messe in April and the 2016 International Manufacturing Technology Show in Chicago in September. There's also the matter of the U.S. presidential elections in November, which promise to shape policy in manufacturing for years to come.

But the year started with global economic turmoil, as a slowdown in Chinese manufacturing triggered a worldwide stock hiccup that sent values plummeting. The continued plunge in world oil prices has resulted in a slowdown in exploration and, by extension, the manufacture of exploration equipment.

Read more: 2015 Salary Survey

Maintenance and reliability tips and best practices from the maintenance and reliability coaches at Allied Reliability Group.
The One Voice for Manufacturing blog reports on federal public policy issues impacting the manufacturing sector. One Voice is a joint effort by the National Tooling and Machining...
The Society for Maintenance and Reliability Professionals an organization devoted...
Join this ongoing discussion of machine guarding topics, including solutions assessments, regulatory compliance, gap analysis...
IMS Research, recently acquired by IHS Inc., is a leading independent supplier of market research and consultancy to the global electronics industry.
Maintenance is not optional in manufacturing. It’s a profit center, driving productivity and uptime while reducing overall repair costs.
The Lachance on CMMS blog is about current maintenance topics. Blogger Paul Lachance is president and chief technology officer for Smartware Group.
The maintenance journey has been a long, slow trek for most manufacturers and has gone from preventive maintenance to predictive maintenance.
Featured articles highlight technologies that enable the Industrial Internet of Things, IIoT-related products and strategies to get data more easily to the user.
This digital report will explore several aspects of how IIoT will transform manufacturing in the coming years.
Maintenance Manager; California Oils Corp.
Associate, Electrical Engineering; Wood Harbinger
Control Systems Engineer; Robert Bosch Corp.
This course focuses on climate analysis, appropriateness of cooling system selection, and combining cooling systems.
This course will help identify and reveal electrical hazards and identify the solutions to implementing and maintaining a safe work environment.
This course explains how maintaining power and communication systems through emergency power-generation systems is critical.
click me