According to U.S. Department of Energy statistics, the mining industry ranks fifth in total motor-system electricity consumption among major U.S. industry sectors, accounting for roughly 5.7% of total industrial motor-system electricity. Along with other industrial sectors heavily dependent on motors, mining stands to benefit from improvements in motor system efficiency resulting from good design, purchase and management practices.

If the results of a recent DOE survey are any indication, there is plenty of room for improvement. The survey found that:

* most motor purchase decisions are made at the plant level;

* 19% of respondents were aware of premium efficiency motors, the common market designation for motors that meet standards promulgated in the Energy Policy Act;

* 4% understand the efficiency ratings associated with the premium or high-efficiency designations and 38% are somewhat aware of these relationships;

* 22% of survey respondents purchased high-efficiency motors in the past year;

* customers most often use the size of a failed motor being replaced as a key factor in deciding the size of the new motor, and 29% use the size of the failed motor as the only factor in the sizing decision, which can lead to persistent motor oversizing and inefficient operations;

* 11% of respondents have written specifications for motor purchases, but only two-thirds of those customers included efficiency in their specifications;

* reducing capital costs is the most important consideration driving customers' decision whether to rewind or replace failed motors.

Underscoring these findings are the results of a 1998 poll conducted by the Energy Cost Savings Council among subscribers to CFO magazine. When asked a series of questions regarding their company's management of electrical energy costs, readers indicated that electrical energy costs are seen by corporate financial officers as the least controllable of several typical business cost categories, including labor and transportation.

Only half of the financial managers polled were familiar with ways to upgrade or retrofit electrical equipment to achieve better control of energy costs. Almost half of corporate financial decision makers said they were not involved in electrical energy-related purchase decisions.

Improving motor efficiency Despite the apparent high level of inattention to electric-motor matters indicated by these studies, there has been a great deal of activity over the past few years among motor suppliers, industry trade associations and government regulatory agencies to develop standards for measuring and labeling motor efficiency. This mainly has been in response to provisions of the 1992 U.S. Energy Policy Act (EPAct), the most recent of which went into effect during October 1997.

In a nutshell, EPAct specifies energy efficiency standards and test procedures for general-purpose electric motors produced domestically or imported. It also directs DOE to establish efficiency labeling requirements and compliance certification requirements for motors. According to the DOE's Office of Codes and Standards, "general purpose" covers 1- to 200-hp, T-frame, single-speed, foot-mounted, polyphase squirrel-cage induction motors conforming to National Electrical Manufacturers Association (NEMA) Design A and B; continuous rated, operating on 230/460 v and constant 60-Hz line power.

Motors now excluded from EPAct requirements are those above 200 hp, operating at 900 rpm or slower, two-speed, 50-Hz, NEMA Design C and D, U-frame units operating at 200/400 or 575 v. A clause in the act's provisions excludes motors designed for "service conditions other than usual or for use on a particular type of application and which cannot be used in most general-purpose applications."

This led to confusion among manufacturers about which of their models are included or exempt from current EPAct standards, and NEMA sent DOE a set of recommendations intended to clarify this gray area in motor coverage.

Nonetheless, most major suppliers have scrambled to revamp their lines of general purpose electric motors to conform with the act's requirements.The added cost of redesign, new materials and other factors involved in producing more energy-efficient motors resulted in price increases of 10% or more. Since the act also affects OEMs, who now must include high-efficiency motors in their products, EPAct's cost impact does not just stop at the last page of the latest electric-motor catalog. It affects a wide range of equipment used in almost every sector of industry.

And, since both stand-alone motors and those used as components in other equipment must be listed or certified in conformance with EPAct, the downstream cost effect will spread as end-users are required to purchase EPAct-standard motors for replacement in HVAC and other common types of industrial equipment.

In an effort to make motor end-users more aware of the availability of high-efficiency models and their performance/cost benefits relative to conventional motors, DOE offers a free software program called MotorMaster+. Now in version 3.0 release, the program was developed by the Washington State University energy program with DOE funding. It is available for download or ordering on CD-ROM at www.motor.doe.gov, where you can also find an online interactive version of the program.

The software is offered as part of the DOE's Motor Challenge program, an industry/government partnership designed to help U.S. industry capture 9 billion kWh per year of electricity savings from higher motor efficiency by 2010. The Motor Challenge program focuses on a few key industrial sectors that participate in DOE's Industries of the Future (IOF) strategy, including the mining industry.

IOF sectors account for 53% of total industrial motor system energy consumption. The initial target sectors of Motor Challenge-paper and allied products, steel, mining, and water supply/wastewater-account for 36% of total industrial motor system energy consumption.

MotorMaster+ allows the user to search for, select and compare current, post-EPAct price and performance data for electric motors offered by major suppliers. The new version was improved to allow users to figure variable load capabilities for motors of interest, as well as to conduct batch analysis of efficiency values over a range of motors. It can be installed on a company's local or wide-area network and used by anyone with access to that network, allowing multiple users to view, edit and update corporate- or facility-level motor inventory databases.

Working smarter In addition to motors that are more efficient than past models, end users now can select from product lines that are smarter and more reliable than their predecessors. Although a complete survey of new motor features is beyond the scope of this article, a quick sampling of recent developments indicates where motor and motor-control technology is headed.

Reliance Electric now offers a line of motors that feature integrated process diagnostics. Its IQ Intelligent line uses the company's PreAlert sensor and software-algorithm system to provide early warning of potential problems. The system monitors a range of motor-operating information, including all phases of current and voltage signature, winding and bearing temperature and vibration signature. Speed-sensing by tachometer or encoder is an optional feature. The system's circuitry is board-mounted on the motor and obtains power from incoming motor line power.

According to the company, the system's microprocessor board holds in flash memory the precise genetic imprint of a motor, and uses algorithms to provide repeatable analysis of sensor input data. The motors can be connected to Rockwell Automation's DeviceNet I/O system or other RS232-based protocols for collection and processing by computer. Once processed, the data can be displayed through MMI (man-machine interface) software packages offered by Rockwell and other vendors.

IQ Intelligent motors are available in sizes ranging from 2 to 500 hp, constant or variable speed, 180-449 frames, in PROT, TEFC or TENV enclosures and in XE premium efficiency designs.

Other motor suppliers are expanding their product lines to include units designed for specific duties. Baldor Electric, for example, has long been active in the variable-speed conveyor-motor sector but recently announced that it will now offer a line of crusher-duty motors through its general distribution catalog that formerly were available only to OEM customers. These three-phase, rigid-base units are rated at 100 to 300 hp and available in NEMA 405T through 449T frames and operate at speeds of 1,180 or 1,780 rpm at 60 Hz.

According to the company, the motors are designed to provide Design C motor pullout torque and lockup torque performance, coupled with extremely high startup torque, in a Design B package. Primarily known as a provider of steel-band motors in the smaller horsepower ranges, Baldor also has developed a range of cast-iron models in the 200- to 800-hp range and recently tested its first 1,000-hp motor.

Toshiba International Corp.'s quarry-duty product line includes motors, adjustable-speed drives and motor starters. According to the company, its quarry-duty motors provide Design C torque, along with oversized bearings, 4140 tensile-strength driveshafts and roller bearings on the drive end to handle heavy radial loads encountered in high-inertia, belt-driven applications. Motors are available in 230/460-v, 460-v and 575-v, 60-Hz versions rated at 1,800 or 1,200 rpm.

Toshiba's G3 adjustable drive comes in several versions, including a NEMA IV, which is said to be highly impervious to dust. Toshiba claims that the infinite speed control, high starting torque and 2-minute overload capacity offered by the G3 line make them particularly appropriate for crusher or vibratory-feeder applications.

TECO-Westinghouse Motor Co. markets a line of stock motors, including their MAX-E1 and E2 premium efficiency, severe-duty, totally enclosed fan-cooled units. Available in standard 460- and 575-v versions as well as other voltages upon request, the motor's sound power levels are below 90 dBa for quiet operation, the company said. Units in the MAX-E1 line can be customized using TECO-Westinghouse's Kwikmod system to meet a wide variety of application requirements.