VFDs help HPUs be more efficient

Aug. 15, 2014

HAWE Hydraulics, Charlotte, N. C., offers an energy-saving alternative to conventional fixed-speed hydraulic power units (HPUs) using variable-displacement pumps. Instead, the industrial HPU drives a fixed-displacement pump at variable speed. This technique drives the pump at the speed necessary to provide the required flow up to 20 lpm – all while maintaining a constant pressure for clamping or other functions.

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HAWE’s NSMD clamping module, used in conjunction with a variable-speed HPU, reduces energy consumption in manufacturing operations by maintaining closed-loop pressure control.

The speed of a variable-frequency drive is commanded by a hydraulic pressure sensor, and its signal is processed in a frequency converter. The rapid reaction time of the control loop prevents pressure drops and peaks when the volume flow requirement changes. It also stops the motor when no flow is required, rather than have a pump operate at near-zero displacement.

HAWE’s NSMD clamping module sets and monitors clamping pressure through an integrated switch; it transmits proportional signals from the machine’s control system to the valve’s proportional solenoid. It not only measures whether the clamping pressure is correct but also evaluates whether the clamping cycle is complete. This means the release signal can be used directly for starting the machine, thus eliminating the need for a pause to ensure the clamping motion is completed.

Machines such as lathes can also operate without the clamping module if the workpiece clamping device is the only hydraulic unit being supplied by the power pack. The clamping pressure can then be set directly via the motor speed. Pressure and volume flows are matched to consumption requirements to ensure correct pressure is applied at the right time.

For more information, call HAWE Hydraulics at (704) 509-1599, go to www.hawe.com, or visit them at IMTS booth E-4930.