Direct drive units are powered by an electric or gas motor. These pumps can achieve a deep vacuum, and they are economically priced. The motor spins at a constant speed, based on the type of motor used.
The pump of these units is directly connected to the drive shaft of the motor, so the pump mirrors the motor in terms of RPMs. With no belts to replace and fewer moving parts, under some conditions, these pumps can last longer. They are also often quieter and have less friction.