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News and Press: Industrial Hydraulics
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[28.08.08] |
Variable-speed Pump Drives from Rexroth Cut Noise, Save Energy - IMTS 2008 |
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Rexroth uses speed reduction on hydraulic pumps to increase energy-savings and reduce noise
(Bethlehem, PA – www.boschrexroth-us.com) Over the past few decades, the technical development of hydraulic machine tools has been driven by the desire to increase efficiency (accuracy, cycle time, etc.). Now, the use of proportional and high-response valves along with variable displacement pumps and electrohydraulic control to improve energy efficiency have been in the foreground. In the last few years, requirements for energy saving and noise reduction have become increasingly stricter. Rexroth responds to these changing market requirements with the use of variable-speed pump drives (DvP).
With variable-speed pump drives, Rexroth opens up new possibilities of cutting lifecycle costs while complying with user specifications. On the variable-speed pump drive Rexroth relocates the closed-loop control into the converter, unlike conventional variable displacement pumps where an asynchronous motor controls the displacement and pressure via internal control mechanisms.
During the non-machining time and partial load operation when no hydraulic flow is required, the frequency converter reduces the speed of the electric drive and the fixed displacement motor. This reduces energy consumption, hydraulic power losses which are introduced into the oil, and noise emission. As soon as the hydraulic system requires more power, the converter adjusts the speed in line with demands.
Rexroth applies this principle in two ways, combining its drive and control expertise in both hydraulics and electric drives. In the first method a high-dynamics servomotor provides the required torques at very short acceleration times. Rexroth’s intelligent converter evaluates command values and the actual values provided by a pressure cell and adjusts the speed accordingly. Pre-parameterized software considers hydraulics-specific controller strategies and automatically compensates for non-linearities of fluid power technology. This method results in remarkable reductions in energy costs, hydraulic power losses and noise emissions.
In the second method, a standard asynchronous motor assumes the drive function. The dynamic Rexroth converter IndraDrive Fc controls the speed of the electric motor, and the control loop is closed using a pressure cell. When operated continuously at low speed, this method requires an external fan on the electric drive motor. Compared with the servomotor method, this solution features significantly lower acquisition costs.
Both methods fit seamlessly into decentralized and central control architectures of machine tools. Depending on the specific machine concept, the manufacturer can integrate the converters from Rexroth in the control cabinet or mount directly on the hydraulic power unit. Speed-related pump drives also cut lifecycle cost when retrofitted to existing machines.
Bosch Rexroth AG, part of the Bosch Group, achieved sales of approximately $7.4 billion (5.4 billion Euros) in 2007 with nearly 33,000 employees. Under the brand name of Rexroth the company offers all drive and control technologies, from mechanics, hydraulics and pneumatics to electronics and associated service. Over 500,000 customers worldwide utilize Rexroth’s unique technological know-how to implement their innovative and future-oriented systems and machine concepts. The global player, represented in over 80 countries, is an extensive supplier of components and systems for industrial and factory automation and mobile applications. Visit www.boschrexroth-us.com for more information.
For more information, please contact
Bosch Rexroth Corporation
Aaron Weida
2315 City Line Road
Bethlehem, PA 18017-2131
Telephone (610) 694-8298
Fax (610) 694-8339
aaron.weida@boschrexroth-us.com
Godfrey Public Relations
Todd Walter
40 North Christian Street
Lancaster, PA 17602
Telephone (717) 393-3831 ext. 133
Fax (717) 393-1403
twalter@godfrey.com
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