Engineering and Mining Journal - Whether the market is copper, gold, nickel, iron ore, lead/zinc, PGM, diamonds or other commodities, E&MJ takes the lead in projecting trends, following development and reporting on the most efficient operating pr
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MOTORS & DRIVES 50 E&MJ; • APRIL 2016 www.e-mj.com The Driving Force Motors and drives perform critical service throughout any mining operation. E&MJ; looks at the latest equipment for powering crushers, conveyors, pumps, fans, hoists and much more. By Simon Walker, European Editor Electric motors are the workhorses of any industrial operation, with mining and mineral processing being no exception. From the most powerful, driving hoists, crushers and mills to the smallest fi tted to equipment such as reagent dosing pumps, motors keep the process moving. In consequence, reliability is abso- lutely essential; a failed motor or drive on a critical component can, in a worst- case situation, stop the entire system in its tracks, and even where redundancy is designed in, a proportion of the process capacity will be lost until the problem can be fi xed. Where a big machine is involved, the impact can be severe: as Newcrest Min- ing reported last year, the discovery of loose windings in the motor driving one of the SAG mills at its Cadia operations led to the mill being out of action for several weeks. While investigations into the prob- lem were under way, Newcrest decided to install a new conveyor to bypass the mill temporarily, with the fi nal verdict being that a full motor rewind will eventually be needed as part of the mill maintenance program. Clearly, the situation could have been worse, especially if it had been deemed that running repairs were insuffi - cient to keep the unit running while long lead-time parts were being sourced. For this review, E&MJ; asked several major suppliers of motors and drives for information about the systems they offer for different static applications. What is the Application? Toshiba products for the mining and min- erals industry include induction, wound rotor and synchronous motors, UPS, pro- cess and intelligent controls, motor con- trols, and power distribution protection solutions. The company reported that it has supplied mining operations through- out North America and South America, as well as in Australia. Toshiba explained that although mo- tors may appear to be the least complicat- ed component of mining equipment, ap- plications require unique analysis of the location, operational behavior and con- ditions to defi ne the features for long motor life correctly. Mining requires rugged, durable motors for continuous operation that are relatively mainten- ance-free and are designed to operate safely and effi ciently in hazardous and severe conditions. Basic motor specifi cations begin with determining the often unique require- ments of the application. For instance, is the application shaft-up with heavy belt- ing conditions, as often found in fl otation or separation processes, or is it for high- torque, high-power connected motors for high-pressure grinding rolls? Does the motor require constant torque and horse- power or does it cycle on a regular basis around the clock? To select an induction motor correct- ly for a mining application, the speed vs. torque curve requirements of the driven equipment should be understood. For example, a particular motor may operate well on a centrifugal pump application, but will be unable to bring a full gyratory crusher up to speed because of the differ- ent starting torque requirements. Toshiba's product lines for mining-in- dustry use include its general purpose EQP Global motor series, which is avail- able in sizes from 0.75 hp to 500 hp. Designed for heavier work in sizes from 1 hp to 600 hp, the company's Quarry Duty motor has a totally enclosed fan- cooled design and provides high starting torque, with oversized superior-grade roll- er bearings, and shafts built with high- strength 4142 steel to withstand the harsh working conditions. For applications in potentially haz- ardous atmospheres, Toshiba's explo- sion-proof motors (0.75-300 hp) are totally enclosed and are equipped to con- tain an internal explosion as well as to prevent emissions. The company claims that its medium- voltage motors are some of the toughest available, meeting the industry's need for better reliability and energy effi cien- cy. Completely customizable, they are available in open drip-proof, weather-pro- tected type I and II, totally enclosed fan- cooled, and totally enclosed air-to-air cooled enclosures, in sizes from 100 to 50,000 hp (75-37,285 kW) and for volt- ages from 2,300 to 13,800 V. A Toshiba 2,000-hp high-speed vertical hollow-shaft motor for deep dewatering.