Controlling rising energy costs with VSD

Whilst a majority of food processing plants use compressed air as their major power source, many are unaware of the significant cost and the potential energy savings that can be achieved through the application of variable speed drive (VSD) technology, which can lower the cost of compressed air by as much as 35%.

Energy expenses contribute more than 70% of the long-term cost of owning an air compressor. Over the life of a compressor, energy costs will add up to many multiples of the original equipment investment. Often, much of this energy is wasted through inefficient part load controlling of the compressor.

During production periods, air demand can vary considerably. Using variable speed drive technology to match compressor output to demand, excessive energy consumption caused by wasted ‘off load’ power can be reduced.

As wasted energy is reduced, savings of as much as 35% are possible. Significant energy savings will generally result in the additional cost option of a variable speed drive typically being recovered very quickly.

VSD — controlling your energy costs

In VSD systems, the compressor rotational speed is automatically adjusted to match output to demand. The compressor carefully varies its output, as demand constantly varies throughout the production period. The system pressure is maintained at a constant set point, which is lower than that of a fixed speed compressor, saving additional energy.

Key features of a VSD compressor include:

• Gradual motor speed ramp-up, eliminating starting current spikes
• No limitation on the number of motor starts
• Excessive part load energy consumption eliminated
• Steady system pressure
• Lower plant pressure, reducing artificial air demand
• Reduced plant leakage due to lower system pressure
• Reduced noise levels
• Wide turndown range

Networking for up to 16 compressors

On board every SCCA VSD compressor is a PLC-based controller that takes care of both the compressor functions and the integrated Schneider Altivar 61 inverter. The controller also offers networking capabilities for up to 16 compressors. The speed of the motor and direct-drive air-end combination are controlled to exactly match output to demand at steady pressure. At part load, compressor shaft power varies almost linearly with demand. The inverter is independently cooled, allowing operation in ambient temperatures up to 50°C. The Altivar 61 is protected against damage from dust and moisture in the harshest environments.

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