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Automation Articles
Motor Management In Control Panels Drives Energy Savings
[2009-05-06]

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By Fabrice Meunier
Business Development Specialist
Schneider Electric


Contrary to the world's challenged economic health, energy costs continue to escalate. Better management of energy consumption and the reduction of resultant costs will be an essential component to a company's economic well-being for the near and distant future. In the 21st century industrial manufacturing facility, maximized energy and cost savings increasingly means more astute management of electrical motors, because motors account for more than 50 percent of a typical facility’s energy consumption. This can be done via motor management measures incorporated within control panels.

This article will illustrate how to save energy by using low power dissipation motor starters, how smart motor control systems can be used to optimize energy use, how power monitoring systems can help better manage energy consumption of electrical motors, and finally, how variable speed drives can be utilized for energy savings.

Low power dissipation motor starters
Energy consumption by electrical motors accounts for a major portion of the energy usage of a typical facility. However, the power dissipated by motor starters themselves can be significant, and can range from a few watts to multiple watts depending on the type of motor starter used. This translates to thousands of dollars of energy costs per year if a facility has, for example, 100 motor starters installed. Traditional motor starters usually have three sets of power contacts (short circuit protection, contactor and overload relay) and use unmanaged electrical coils to close the contactor poles. To minimize this power dissipation, an all-in-one electronic motor starter can be used. These devices only have one set of power contacts (and can therefore reduce by a factor of three the power dissipated in the power circuit); plus they now utilize low consumption electronic coil control.

These advanced, low power dissipation motor starters can dissipate as little as 3W for a 12A load, compared to 15W to 20W from a traditional, combination motor starter for the same load. This translates to significant energy savings over time.

Smart motor control systems
Before a facility can save substantial energy, management first needs to clearly understand how and where energy is used in its facility. As in any other problem-solving situation, one first needs to clearly measure and understand the current situation before taking any corrective action. This is where smart motor control systems with energy management features become very useful.

These motor control systems are able to precisely measure power and energy consumption at the load level. They are also able to send warnings to programmable logic controls (PLCs) or Supervisory Control and Data Acquisition (SCADA) systems through communication networks if power consumption exceeds a pre-defined threshold. These features will help management to better run their facility and find ways to optimize their overall energy savings. Smart motor control systems are essential to determining if electric motors are running correctly. These systems may detect abnormal running conditions, for example when motors are at end of life. In this situation, electric motors are likely to use more energy than in normal conditions. Smart motor control systems that can detect these end-of-life situations are essential to better energy management.

Power monitoring systems
Getting detailed power and energy consumption at the load level is important information to have. However, the ensuing amount of data, and the management of this data, can quickly become overwhelming. This is why smart motor control systems must be configured to seamlessly connect to SCADA and advanced software packages for power monitoring. These flexible systems can quickly sort and organize data provided by hundreds of smart motor control systems. They are also able to provide summary reports that will allow management to better utilize energy in its facility.

The first critical point is to choose a motor control system flexible enough to connect directly to advanced power monitoring systems. The second critical point is to choose the right power monitoring system which embeds pre-defined device types for the motor control system to use. A pre-defined device type will allow direct readings of critical monitoring variables without having to fully integrate the operational details of the smart motor control system.

Variable speed drives
It’s a fact that some of the electric motors used in facilities do not need to operate at full speed all the time. When a reduced speed is acceptable for part of a process at certain times of the day, variable speed drives will help greatly reduce a facility’s energy consumption. If electric motors are required to start and stop very frequently, the use of a soft start will limit current peaks when the electrical motors start, and therefore help to reduce energy consumption.

However, a variable speed drive or a soft start is not the solution to every electrical motor starter application. In fact, if electric motors have to run full speed at all times, or if they do not start very frequently, the use of a variable speed drive or the use of a soft start will actually use an unnecessary amount of energy. For those applications, it is better to use a motor control system with low power dissipation.

Fabrice Meunier, Schneider Electric Business Development Specialist, graduated in 2001 with a master's degree in electronics and computer science (Paris, France). He is currently pursuing a master’s degree in business administration at North Carolina State University.

 

Quoted From: http://www.automation.com/resources-tools/articles-white-papers/motor-drives-control/motor-management-in-control-panels-drives-energy-savings







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