Servo drives designed for torque, frameless or direct drive motors require high switching frequencies in the range of 40 to 125 kHz depending on the motor electrical time constant. This is achieved by using transistor technology with low switching losses and perfectly tuned gate drivers in order to control the heat generated by the servo drive. As direct drive motors typically have a large pole count, the motor controller must be able to handle high electrical frequencies to properly and efficiently commutate the motor.
Direct drive motors are linked directly with the load. This implies that in order to have a good accuracy, high resolution encoders must be used and in order to prevent homing procedures on startup, absolute encoders are preferred.