What is it about?

This work has been undertaken to help users of motor drive systems maximise the efficiency of their installations. When AC motors are operated from Variable Speed Drives (VSD) there are drive settings available at installation that can help improve the efficiency of the system. But how can the system efficiency be maintained once the equipment is in service? The work proves that decreases in system efficiency caused by deteriorating motor conditions can be measured. By measuring and evaluating key operating data from the motor, it is possible to compare current operating data against data obtained when the equipment was first put into service. This will allow any early deteriorations in equipment to be rectified, mainting the efficiency of the plant and guarding against unexpected failure.

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Why is it important?

Most inverter drive installations for motor efficiency savings tend to be installed then left to run with little or no operational checks during the lifetime of the installation. Intervention may only occur when there is a failure of plant equipment, not a gradual deterioration in efficiency. On installations with many larger motor sizes of 100's of kW, savings of 1-2% per annum can have a significant impact on annual energy costs. Keeping equipment operating at it's most efficient point maintains the predicted energy savings over the lifetime of the equipment, maximises the return on investment and can extend the operating life of equipment.

Perspectives

Having designed many motor drive system projects for industrial applications at Optima Control Solutions I have always had a keen interest in helping customers get the most out of their investment. Whilst machine performance is almost always improved with a drive control system upgrade it would be useful to be able to benchmark the machine energy efficiency post-upgrade compared to what it was previously. The customer then realises another benefit of the upgrade that may not have previously have been apparent. It has been interesting to discover that open loop and sensorless vector drive modes not only affect motor performance but can have effect the efficiency of the whole motor drive system. It may be worthwhile spending that little bit more on a Sensorless Vector equipped drive as the costs may be recouped quite quickly with the energy savings obtained.

Mark Lane
University of Huddersfield

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This page is a summary of: Investigation of reductions in motor efficiency and power factor caused by stator faults when operated from an inverter drive under open loop and sensorless vector modes, Systems Science & Control Engineering, January 2017, Taylor & Francis, DOI: 10.1080/21642583.2017.1367734.
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