We will start with the servo drive. The combination of servo drive with the servo-motor It allows a very precise and fast control of the position, this being the main application of servomotors. For this, a check must be carried out in closed loop, that is, the control receives through a encoder information on the real position of the motor shaft (output) and performs a readjustment of the control based on that information. The control adjusts the output based on the input and the deviation in the output with respect to the setpoint. In this way one reaches a high position accuracy.
The frequency inverters are normally used when you want to control the speed. In cases where it is required to increase its precision, a closed-loop control will also be necessary, although in most cases an open-loop control is sufficient, that is, the control adjusts the output based solely on the input, and there may be greater deviation depending on the load, for example. As has been said previously, although a closed loop is used to control asynchronous motors, due to their construction characteristics they have a greater inertia and a lower peak current than servomotors, so they are not recommended if a fast and reliable control is required. accurate position and even less if you work at low speeds.
typical examples of servo motor applications are the machines pick and place, court, labeled and of course in robots. They require very precise control of position and speed. In addition, servomotors are especially indicated when it is necessary to work at low speed with high torque.
Are used frequency inverters for the control of the pumps used in the irrigation systems, heating or air conditioning, also for the movement of conveyor belts or elevators where loads are high and variable.
Conclusion:
Although the frontier between the two types of control is becoming more blurred as there are closed-loop frequency inverters that allow position control, the most common, taking into account the cost, the type of control and the associated motor, is to use a servo drive with servomotor when great precision in the position is required and frequency variator in case of needing speed or torque control.