Within the drive systems of air compressors, five primary configurations are typically distinguished: direct drive, belt drive, gear drive, integrated permanent magnet drive, and the comparatively less common hydraulic drive.

Direct drive

The direct drive of a screw air compressor refers to the connection between the motor shaft and the rotor of the compressor through a coupling. However, this is not a true direct drive in the strict sense. The direct drive in the true sense means that the motor is directly connected to the rotor and the speed of the two is the same, which is obviously very rare. Therefore, the notion that direct drive involves no energy loss is not accurate.

Belt drive

This transmission method allows for the adjustment of the rotor’s speed by using pulleys with different diameters on the belts.

Gear drive

Gear transmission constitutes an essential core component of centrifugal air compressors. It is employed in large-scale industrial screw compressors and certain high-end oil-free air compressors. Owing to its highly precise construction, it delivers exceptionally high transmission efficiency. Although manufacturing costs are comparatively high, it ensures correspondingly reliable operation.

Integrated permanent magnet drive

Permanent magnet synchronous drive represents an advanced form of direct drive transmission, primarily utilising permanent magnet synchronous motors. This technology integrates the rotor with the compressor host rotor directly onto a single shaft, thereby eliminating intermediate transmission stages and reducing transmission losses. It constitutes the key technology enabling high energy efficiency in the new generation of premium variable frequency screw air compressors.

Hydraulic drive

Hydraulic transmission, a less commonly employed method, transfers power via hydraulic couplers or torque converters. Its advantage lies in enabling flexible starts, effectively protecting both the motor and grid even during no-load motor starts. Its disadvantage is relatively low efficiency, coupled with inherent fluid losses.

It finds application in scenarios requiring heavy-load, high-power starts or in diesel-powered mobile air compressors, though such usage is now uncommon.