Using an AC variable frequency drive (VFD) to control a large air compressor in a pump manufacturing plant not only helped the plant save energy, it also resulted in the air compressor running much more quietly. The rotary screw compressor was using too much energy because its capacity exceeded the needed output of compressed air. Because the compressor ran for six or seven days a week and for two to three shifts every day, the unit consumed large amounts of electrical power.
Fixing leaks, no help
An energy audit revealed minor leaks, but fixing them resulted in an improvement of only 2 percent. The audit also revealed that the operation of the compressor was not optimized to the needs of the plant. To remedy this situation, engineers suggested using an AC variable frequency drive (AC drive). Compared to load/unload control, inlet modulation, or geometry control, the use of an AC drive results in more efficient operation and thereby lowers operating costs.
Optimizing compressor operation
To adjust the compressor output to the needs of the plant, engineers installed a Parker 200 HP AC890PX AC drive. This allowed lowering the speed of the compressor while maintaining the required air pressure, which significantly lowered the unit’s electrical consumption. The base drive unit includes a lockable AC disconnect, line fuses, and a 3 percent line reactor to guard against harmonics.
Under the hood of the AC890PX
The AC890PX series AC drive comes in ratings from 150 HP to 600 HP, with standard input voltages of 380, 415, 460, 575, and 690 V. The unit can be used with induction motors (with or without feedback) as well as PMAC servo motors without modification. The drive includes a dynamic braking switch, resistor, AC line disconnect, 3 percent AC line reactor, and programming keypad. The pluggable modules are lightweight, and can be installed without requiring a service call. An active front end is available that allows continuous regeneration at full load with negligible power line harmonics and at unity power factor.
Our success factors
- Commonality of replacement parts with other installed VFD drives
- Past history of successful AC890PX installations on different applications
- Fast and easy commissioning of VFD, as proven by experience
Benefits to the pump manufacturer
- Energy savings of 22 percent (ROI in under a year)
- Less wear and tear on compressor components due to soft, controlled starts
- Lower peak demand for electric power due to soft starting
- Noticeably quieter operation
- Improved power factor – VFD includes 3 percent line reactor
The next time you are looking for energy savings in your factory, consider variable frequency drives and team up with Parker for a fast and easy commissioning.
This article contributed by Lou Lambruschi, Marketing Services and E-Business Manager, Parker Hannifin Corporation SSDN/Energy Grid Tie Division
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