Consider a variable frequency drive (VFD) to provide a quiet, energy-saving operation on a hydraulic power unit (HPU). An HPU can make for an interesting example of a hybrid system that combines electronics (variable frequency drives) with hydraulics (hydraulic pumps).
HPU application challenge
For example in one case, a large aircraft manufacturer needed a hydraulic power unit with a capacity of 3500 to 5200 PSI. Typically, the company would have used a variable displacement pump, with the AC motor running at a fixed speed for this kind of application. However, because of the hydraulic power units’ intended location in the plant, the typical configuration would have been too noisy and produced too much vibration. In addition, the system’s long periods of idle time would have wasted energy because the 200 HP motor would remain running at all times.
A hybrid alternative
The alternative hybrid system included two 200 horsepower (HP) induction motors, Parker AC890PX VFDs, and hydraulic pumps and associated equipment, including another Parker drive for a 25 HP cooling pump that also serves to maintain minimum system pressure during idle. The drives communicate via Ethernet with Parker human machine interfaces (HMI) and the plant’s supervisory control and data acquisition (SCADA) system.
Details on the Drives
The AC890PXs have a modular design, which provides several benefits. For instance, two drives easily fit into an accessory cabinet containing the HMI and logic, thereby forming a compact lineup for installation in the control room. In addition, the bottom wire entry option let the wiring be run through the floor, resulting in a simple and clean installation. The drives also provided increased operator safety thanks to the standard “Safe Torque Off” feature.
What’s more, the drives have plug-in power elements that can easily be changed with just an Allen wrench. The variable frequency drives accommodate small, energy efficient hydraulic pumps that maintain a minimum pressure in idle mode, allowing the 200 HP motors to be shut down.
For more information, please visit Parker SSD Division to learn more about VFD HPU applications
Article contributed by Lou Lambruschi, marketing services manager for Parker Hannifin Corporation Electromechanical and Drives Division
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