Drive Technology Guide: Motors, Torque, Variable Frequency Drives | TEA

Drive Technology: Fundamentals of Motor Selection

Drive technology forms the heart of every machine. Motor, gearbox, and controls must be considered as a system — only then can efficiency, dynamics, and reliability be optimally balanced.

Motor Types at a Glance

Three-Phase Induction Motor

The three-phase induction motor is the most widely used industrial motor. It is robust, low-maintenance, and cost-efficient. Its efficiency is 85–95 % (IE3 class). Drawbacks: limited dynamics, fixed speed without a drive inverter.

Servo Motor (Permanent-Magnet Synchronous Motor)

Servo motors offer high dynamics, precise positioning capability, and high starting torque. They are always operated with an encoder and servo drive. Costs are higher, but they are indispensable for axis applications in CNC, robotics, and handling technology.

Gear Motor

Gear motors combine a standard induction motor with a gearbox (typically spur, planetary, or worm) into a compact unit. Advantage: simple installation, defined output torque and speed without a separate coupling.

Torque: The Key Sizing Parameter

Torque is the most important parameter for motor selection. It must be reliably available in all operating states — start-up, operation, and braking ramp. In addition to rated torque, pull-up torque and thermal limit torque are also relevant.

Variable Frequency Drives: Applications and Limitations

Variable frequency drives (VFDs) enable stepless speed control of induction motors. Typical energy savings in pump and fan applications: 30–50 % compared to throttle control. Important: not all motors are VFD-rated; use IE3 motors with rated voltage and the appropriate insulation class.