Rotary screw air compressor motors typically come in two varieties: belt drive and direct drive. In a belt-driven air compressor, a belt connects the motor to the compressor pump — as the motor turns, the belt turns with it, activating the pump. In a direct drive motor, as the name suggests, the motor attaches directly to the compressor crankshaft.

Belt and direct drive models both have advantages and disadvantages inherent to their working principles. The right choice for you will depend on several different factors. In this post, we’ll look at how a direct drive air compressor works and explain some of the main benefits — and potential applications — for this type of machine.
WORKING PRINCIPLES
All air compressors require a power source — for most models, it’s an electric motor. While several design factors influence a compressor’s pressure and capacity rating, the size and efficiency of the engine also contribute. As a general rule, every five CFM of 100 psig compressed air a unit produces require at least one horsepower of engine power.

How the motor transfers power to the compressor itself is a critical distinction between rotary screw compressors. Belt-driven models allow for greater flexibility, as they can be adjusted to deliver varying amounts of air flow pressure and capacity. Direct drive models, on the other hand, attach either directly or via a flange. As a result, they’re less adjustable but more efficient. Manufacturers often sell smaller HP direct drive compressors as a single integrated package.
DIRECT DRIVE ADVANTAGES
The unique design of the direct drive model offers several benefits to users. Most critically, direct drive compressors have fewer moving parts and, as a result, fewer components that can incur wear and tear. This quality makes them better-suited for heavy duty industrial applications where a belt-driven model won’t do.

Direct drive compressors are more efficient, as less power is lost during transfer from the motor to the crankshaft. While direct-driven models are often more expensive to purchase outright, that initial investment is repaid over time, as they’ll require less fuel over the life of the unit.

Products such as the Atlas Copco Compressors feature specially designed acoustical enclosures to keep running volumes to a minimum.