Nearly three decades ago Peter Achten, CEO of Innas BV, had the idea for a hydraulic transformer but the concept didn’t take off because hydraulic pumps of the day could not work with the technology.
Innas’ hydraulic transformers have performed well in field tests, proving their viability for mobile machines.
The concept gained real traction with the development of the Innas’ floating cup displacement principle, which now serves as the foundation for both high-efficiency pumps and motors, as well as Innas’s new generation of hydraulic transformers.
The Floating Cup principle features cup-like cylinders which are carried and supported by a rotating barrel plate. The cups are hydrostatically balanced: they ‘float’ on the barrel plate. Each cup is paired with a piston having a ball shaped piston crown. The piston crown has a cavity. The dimensions of the cavity are chosen so that the expansion of the piston crown equals the expansion of the cup.
The ball-shaped piston crown has the same outer diameter as the inner cylinder of the cup. The resulting sealing line is always perpendicular to the main axis of the cup, irrespective of the tilt position of the piston. Consequently, the radial pressure load on the cup is equal in all directions. The cup is therefore completely balanced and does not create a hydrostatic load on the piston, which minimizes friction and wear.
Innas’ Floating Cup principle features cup-like cylinders which are carried and supported by a rotating barrel plate. The cups are hydrostatically balanced: they ‘float’ on the barrel plate.
The cups are floating, but the pistons have no chance to move. They are press fitted into the rotor, onto the main shaft. The oil column creates a hydrostatic force on the piston, having the same tilted position as the cup. The shaft torque is created by the radial components of these piston forces. The conversion of hydraulic power to mechanical output power is direct: there are no moving interfaces or linkages. As a result, there are also no principle losses.
Now that the floating cup concept is proven for hydraulic pumps, the company has now made its hydraulic transformer available, highlighting it at bauma 2025 in Munich, primarily for autonomous machines.
“The transformer was always the goal,” said Achten, “but the industry wasn’t ready. We had to first introduce a new displacement principle.
“When you want to control a cylinder, it is moving back and forth, and it stops and goes, stops and goes. And when it moves, it often moves with maximum load, you want to use a displacement principle like a pump or transformer to move this cylinder. Ideally, this pump should be running at zero rpm to start with the maximum load. And no pump principle could do this at the moment. When we designed the transformer in 1996 and built one, I knew that we had to design a new principle and that became the floating cup.”
Achten said that with the hydraulic industry being so conversative, taking a completely new approach can be challenging. Thus, they first had to develop the floating cup principle up to a point where it was brought into the market, and now that is up and running, it was time to back to the transformer design.
Innas’ hydraulic transformers have performed well in field tests, proving their viability for mobile machines.
“Now we have a transformer which can be operated with speed at a very high efficiency, with low positions, low noise levels, and can handle these high pressures of startup conditions without any problems. We built this into an application at a field test run, and now we’re going to move into a very interesting domain of autonomous control,” Achten said.
Traditional combined hydraulic transformers (CHTs) paired two pump/motors. These designs, dating back to the 1970s and 1980s, rely on mechanically coupled hydrostatic units to convert and control hydraulic power. Typically, one unit is variable and the other fixed, with pressure and flow ratios determined by their respective displacements. These systems tend to be difficult to control, bulky, inefficient, and mechanically complex. They require multiple rotating groups, complex valve coordination, and cannot achieve truly continuous variability. Because each pump/motor contributes its own inefficiencies, the overall system efficiency is low, compounded further during regenerative operation. CHTs also struggle with compactness and smooth operation at low speeds, limiting their practical adoption despite their potential energy-saving promise.
Innas’s new IHT design replaces these dual-unit arrangements with a single, three-port rotating group. Instead of varying the swash plate angle to control displacement, the IHT varies the angular position of a rotating port plate. This changes the timing of the high-, low-, and load-pressure ports relative to the piston motion, continuously adjusting the effective displacement without altering geometry. The result is a compact, continuously variable transformer capable of both transforming and regenerating energy across the full pressure range of a Common Pressure Rail (CPR) system. The IHT can achieve the same transformation ratios as a dual-unit CHT while using roughly half the total displacement. When paired with INNAS’s floating cup principle, it maintains high efficiency, smooth low-speed operation, and reduced noise and vibration — addressing key shortcomings of previous transformer designs. Achten noted that the IHT simplifies hydraulic transformation from a mechanically coupled dual-machine system into an elegant, single-unit device optimized for modern CPR-based hydraulics.
Traditional hydraulic systems often waste significant energy due to throttling losses in valves, unnecessary fluid recirculation, and poor load matching. The hydraulic transformer addresses these inefficiencies. Because it is a closed-loop system, the transformer minimizes throttling and bypass losses common in open-circuit valve systems. Additionally, with adaptive lead matching, the system continuously adjusts output pressure and flow to meet real-time load demands, improving energy utilization. And finally, it has regenerative capability. Overrunning loads can drive the transformer in reverse, recovering energy and feeding it back into the primary circuit or into an accumulator for reuse.
In lab and simulation tests, Innas reports overall system efficiency gains of up to 50% when replacing conventional valve-controlled systems with transformer-based architectures.
Innas’ hydraulic transformer is compatible with many digital control architectures, such as electronic swashplate control, sensor-Driven feedback loops, and programmable logic integration.
These capabilities make the hydraulic transformer suited for modern applications demanding high performance, precision, and energy efficiency such as mobile off-highway machinery, industrial automation, and hybrid and electric drives.
With the transformer, Achten says it gives machine builders a retrofit or quick-change system to move from an internal combustion engine-driven pump to an electric-driven easily and even at the last minute. Because everything is connected, you cannot just take away one component because those structures would fall apart. What Innas hasto offer is a system to deliver energy and low emissions with the highest efficiency and the lowest cost.
“We’ve opened hydraulics to a new world. We are running into a world where we have been limited by our technology for a number of decades and we have failed to innovate to a large extent,” Achten said. “What we’re trying to do is move hydraulics in the same direction as what electric drives have been doing for many years already. We’re creating smart hydraulics, and extremely efficient for our customers and our industry.”
Innas BV
innas.com
Filed Under: Components Oil Coolers, Pumps & Motors, Technologies, Trending
