How Variable Speed Drives Become Simpler and More Efficient

You are already interested in variable speed pump drives, which save up to 70 percent energy compared to conventional drive solutions. But you are still hesitant due to their greater complexity. For you, Parker has now developed a new, innovative variation of its Drive Controlled Pump - the combination of an optimized axial piston pump with two displacement volumes and a very compact synchronous servo motor offers decisive advantages over common variable speed pump systems. 

For speed-variable applications, pumps with a constant displacement such as internal gear pumps and vane pumps are most often used. The maximum torque is always achieved at maximum pressure. This results in a high motor current for the drive system, which is determined and set by the frequency inverter. Variable pumps are a further option for adjusting the displacement of the pump, reducing the required maximum motor torque. If you want to set the displacement directly, you will need a displacement controller which is comparatively expensive. That is why Parker now offers a new variant of its PVplus axial piston pump: the dual displacement pump. The pump displacement can be switched between two continuously adjustable settings. When combined with a variable-speed drive, you get the following advantages:

• Low torque due to de-stroking in pressure holding, resulting in reduced acquisition costs for the motor and frequency converter
• High traverse speed through up-stroking when in rapid drive mode
• No discontinuity in the movement since no changeover between multiple pumps is required
• Easier pipework and commissioning
• High operating pressure, high productivity and high energy efficiency 

In combination with the Parker GVM-series synchronous motor, which is connected without a coupling or bell housing via a wave-in-shaft system to the pump, results in a very compact, dynamic unit for a wide range of applications. Drive power of up to 125 kW rated power and 400 Nm rated torque are currently available. Another build size is being developed with a peak torque of up to 800 Nm. The liquid-cooled motor can produce the same output at half or a quarter of the size of the normal IE3 motor, without any of the annoying fan noise. Due to its high heat capacity, water is especially suitable as a coolant, but you can also use mineral oil and water glycol. The permitted inlet temperature sits at up to 65°C, enabling direct cooling via the cooling circuit of the hydraulic unit.

Particularly for applications like presses, where the pressure and flow rate requirements vary greatly during the work cycle, the Drive Controlled Pump system was extended by the dual displacement pump with a liquid-cooled synchronous motor. This solution combines the capability of Parker’s axial piston pumps series PVplus with the high dynamics and power density of the GVM synchronous motor. It enables to reduce the required torque compared to fixed displacement pumps even in demanding applications and thus to design the drive system smaller and more cost-effective. The installation and commissioning of the pump used are like conventional solutions. In addition to this, no multi-variable control is required which makes operating the system easier.

Learn more about Parker’s Drive Controlled Pump and the variation with dual displacement pump and GVM motor in a detailed technical article or on our Drive Controlled Pump information page. 

Article contributed by Dr. Ing. Roland Bublitz, industrial applications engineering manager at Hydraulic Controls Division Europe in Kaarst, Germany.

Related content for you

VFD Provides Energy Saving on Hydraulic Power Unit | Case Study

The Hydraulic Solution for the Evolution of Electric Drives

Essential Criteria for Selecting the Right Motor for your Hydraulic Application

Energy-Saving Hydraulic Systems Using Drive Controlled Pump (DCP)