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Drive train efficiency yields solid gains

Supplier: SEW-EURODRIVE
03 October, 2013

Consideration of the 'total systems efficiency' of a drive solution allows quarry operators and OEMs to save energy and maintenance costs, while improving site safety.

The implementation of efficient drive systems is likely to become a priority for the Australian quarry industry in the future. A new generation of drive technology, combined with a 'total systems' approach to optimising efficiency, promises to yield huge savings for all motor-driven industrial activities--conveyors, crushers and other quarry equipment included.
 
SEW-Eurodrive's Industrial Gears National Product Manager, Ian Tribe, points out that efficiencies in a drive system are subject to a 'multiplying effect'. That is, the efficiencies of each element in the complete drive train--from motor and electronics to gear unit, belt or chain--multiply together to determine the total power transmitted. Thus, poorly-designed drive equipment or an excessive number of components in the drive train both severely compound overall losses.
 
The fact is especially relevant to quarries, a number of which still utilise legacy V-belts or chains and sprockets.

"In the past, there were not many gear ratios available, and the systems were designed to provide a flexible means of speed adjustment. But they certainly weren't ideal in terms of efficiency," says Tribe.
 
Close-coupled design

Today, customers have access to many more gear ratios, and efficient and flexible drive systems can be readily achieved with a single customised gear unit. Through this 'close-coupling', not only are the number of drive elements and overall transmission losses lower, but the system has no exposed moving parts--and therefore requires no guards--making it safer and easier to maintain.
 
For SEW-Eurodrive, a number of technological innovations are behind the preference of its gear units over other forms of speed reduction. Modularity is a key feature, allowing a large number of possible gear ratios. Quality and careful gear design are also critical, with inefficient gear configurations, such as single-stage worm gears, avoided.
 
The focus on total drive train efficiency necessarily extends to motors. Further to its range of geared-motor offerings, SEW-Eurodrive continues to expand its efficient DR motor series by recently releasing the DRC motor range with its efficiency surpassing the highest efficiency class IE4.
 
Selecting efficiency

However, as Tribe points out, the benefits from using such high-efficiency drive equipment can be seriously undermined if not suitably matched to the application requirements. He says that motor efficiency is generally best when operating between three-quarters and full load. The mistake that some users make is to select oversized equipment in order to cover extreme demands, but which means that the motor is running mostly at half-load or less.
 
"The 'guess a size and double it' approach means that the customer will pay more through the life of the equipment," says Tribe.

The alternative is accurate selection and sizing of equipment. SEW-Eurodrive engineering staff perform calculations to ensure that each drive element is finely tuned to meet the load requirements, with the motor running at close to full power. Increasingly too, SEW-Eurodrive customers are seeking these in the form of a customised drive package, in which all drive elements, including motor, brake and gear unit, are mounted to the same base.
 
Finally, efficiency gains and greater control over speed adjustment can be simultaneously achieved through the use of drive electronics. Tribe says that inverter technology is becoming increasingly affordable, as evidenced by the growing popularity of SEW-Eurodrive's MOVITRAC® LTP B series. Tribe explains that this inverter series is particularly suited to the industry; being available in a robust IP55 enclosure for the complete power range.

"With the inverter, you're getting better control of the motor enabling electronic adjustment of the process speed. The power factor is always pretty close to unity so, even when partially loaded, you're saving energy."