Ultima oil-free compressor offers major energy savings and smaller form factor

16 June, 2017

Unique drive optimisation – no gear box required

Unlike standard oil-free compressors, which have a single motor and mechanical gearbox design to drive the low- and high-pressure air ends, Ultima uses the U-Drive concept – two, high-efficiency, permanent magnetic motors which replace the gearbox and single motor.

These variable-speed motors, powered by an inverter, can achieve speeds of up to 22,000 rpm and deliver efficiencies greater than IE4.

While conventional variable-speed machines are already well proven in numerous applications and deliver high energy efficiency, the two stages of compression are linked mechanically, meaning they need to speed up and slow down at the same time.

Ultima, however, is different. By removing the gearbox and single motor entirely and replacing with two U-Drives powered by two separate inverters, each airend stage is now driven directly and independently, for even greater performance. An intelligent digital gearbox design then monitors and adjust the speeds of each aired continuously, ensuring maximum efficiency and pressure ratios at all times.

In addition, the design of the compressor results in hugely reduced friction, resulting in an oil-free compressor with the highest levels of efficiency throughout its full turndown range.

Ulrich Thomes, senior technical engineer from Gardner Denver, who led the engineering team responsible for Ultima’s unique design, commented: “From the outset we had clear requirements for the specification of Ultima’s drive unit and found that no current-generation motor was able to deliver the efficiencies required. U-Drive is a true, next-generation motor and the result of three years’ development. We believe that this is one of the most advanced compressor drive technologies available to customers today and ideal for a pioneering product such as Ultima.”

Historical context

Richard Hilton, product director-industrial compressors at Gardner Denver, explained: “Conventional oil free compressors were first designed in the 1960s and ’70s, and were never designed to be a variable speed machine. The problem with a two-stage oil-free machine is you have two stages – a high-pressure and a low-pressure airend – and the original design concept was that you had one motor with a large full gear and a gearbox, and that drives both the high-pressure and the low-pressure airend.

“However, because there is only one motor and one drive, when the machine is speeded up up and slowed down, whatever rate you spin or slow one airend down by the other has to slow down by the same amount – if you slow the high-pressure down by 10% the low-pressure goes down by 10%. But, every air and has an optimum level where it is at its maximum efficiency. It may be that the high-pressure needs to slow down by 10% but the low-pressure needs to speed up by 5% to achieve maximum efficiency. There has never been a motor available that can spin a standard airend up to 22,000 rpm without the use of a gearbox.