Acoustic Drives

Qdrive's STAR™ resonant linear motors - alternators are coupled with non-wearing clearance seal piston/cylinder combinations to deliver highly efficient acoustic power and drive loads such as thermoacoustic Stirling (‘pulse tube’) and Stirling cryocoolers. They can also be “driven” by acoustic loads, such as from thermoacoustic engines, to create power. The patented flexure bearing design eliminates the need for lubrication or maintenance and has virtually unlimited life. For product specifications and more detailed information, click on the Acoustic Drive of interest at the bottom of the page.

How It Works

Qdrive’s acoustic drives are similar to a loudspeaker in your home stereo system. A voltage signal is supplied and the speaker moves back and forth in response, pushing and pulling air in time with the frequency of the electrical signal. The same principle applies here, though the device is a bit different. The magnets move, not the coil, and they are supported by unlimited-life metallic flexures instead of paper or plastic. Like a speaker, it needs no oil – an important advantage when using these devices in a cryocooler (cold oil is not useful!). Unlike a speaker, it pushes not air, but typically high-pressure helium (one of two gases that remains a gas below 77K). And because of that high pressure, the moving face area is smaller and stronger – a metal piston instead of a paper cone. The metallic flexures are designed to hold such a straight line of motion that the pistons can be machined with just microns of clearance to their matched cylinders and run without contact or wearing. One other difference with speakers is that they are designed for an inefficient but ‘flat’ response across a wide range of pitch frequencies. Qdrive’s are tuned to resonate at a single driving frequency (we use 50 or 60 Hz because it comes from the wall plugs!) to give high power and efficiency.

STAR Motors Diagram


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