The main characteristics of the servomotor are smooth rotation, high dynamic, low noise and vibration, motor output torque almost proportional to the applied voltage and direction of the torque determined by the instantaneous polarity of the control voltage. The most commonly used type of servomotor is the servo motor powered from an alternating power supply. In this configuration the rotor generally uses permanent magnets, usually made of rare earths. The housing is made of aluminum, the stator consists of a packet of blades and a sensor called encoder and resolver and is responsible for providing feedback signals to the servo inverter.
Through these signals the converter is able to precisely actuate the servomotor. The resolver sensor is a type of rotary transformer, where an alternating electrical signal is applied to the primary of this rotary transformer and in the two output windings, an alternating signal induced according to Faraday’s induction law allows to obtain the speed and position of the transformer rotor shaft. The output signal from the resolver is an analog signal. The output signal of an encoder is a digital signal. Servomotors can be classified as direct current servomotor and alternating current servomotor.