Summary
Many hydraulic systems in industrial plants run their pumps at constant speed, even when the machine needs little pressure or flow, so excess energy is lost as heat. Matching motor speed to the actual load with a variable frequency drive (VFD) is a widely studied approach. This article explains the principles using technical sources, then presents a job by RAT (Robotics and Automation Technology and Engineering) as a WCE case study.

1. Why adjusting motor speed saves energy
The U.S. Department of Energy (DOE) explains that for variable-torque loads such as centrifugal pumps and fans, the affinity laws mean input power varies with the cube of speed, so a 20% speed reduction can cut power by about half. DOE advises obtaining part-load drive efficiency data from suppliers when calculating actual savings [1].

2. Key principles in hydraulic systems
2.1 Hydraulic pumps rarely run at full load all the time.
In many operating periods, a hydraulic system only needs to hold pressure with little or no flow. If the motor keeps running at full speed, much of the energy is wasted.
2.2 Hydraulic power units driven by variable-speed motors
A study in the journal Energies examined a hydraulic power source driven by a variable-speed motor and found about 30% lower energy use during pressure holding without flow, compared with a conventional variable-displacement power source [2]. This result comes from a specific research system; actual savings in each plant depend on the load profile and system design.
2.3 Measurement is part of the system.
Power meters on the control panel show actual electricity use before and after the upgrade and support long-term tracking.

3. Case study: hydraulic system energy saving by RAT
– Scope: Energy-saving upgrade of a hydraulic system with a new control panel housing three inverters
– Panel front: three power meters and a touch-screen HMI
– Client: Cold-rolled steel sheet manufacturer in Thailand
– Duration: 17 March – 18 September 2026 (about 6 months)
– Progress: Plan 100% / Actual 100%

From left to right, the cover image shows the inside of the control panel with three inverters and wiring, the new panel installed next to the existing switchgear in the electrical room, and the panel front with power meters and an HMI. All images were edited with AI so that no individuals or clients can be identified.

4. Observations
Upgrading an operating plant means fitting a new panel into the existing electrical system and scheduling tie-ins to minimize production impact. Installing power meters from the start lets the client verify savings independently.

5. WCE services
RAT (Robotics and Automation Technology and Engineering) provides automation, control, and energy-efficiency upgrades for industrial plants.
To discuss your project: +66 65-937-6283 | international@wce.co.th | www.wce.co.th
We engineer your success.

References (accessed 6 Oct 2026)
[1] U.S. Department of Energy, Advanced Manufacturing Office (November 2012). Adjustable Speed Drive Part-Load Efficiency. Motor Systems Tip Sheet #11, DOE/GO-102012-3730. https://www.energy.gov/sites/prod/files/2014/04/f15/motor_tip_sheet11.pdf
[2] Yan, Z., Ge, L. & Quan, L. (2022). Energy-Efficient Electro-Hydraulic Power Source Driven by Variable-Speed Motor. Energies, 15(13), 4804. https://doi.org/10.3390/en15134804