![]() ![]() ![]() Increasing the rotor resistance linearizes the speed-torque characteristics. We know that the general shape of the torque-speed characteristic of a two-phase induction motor depends largely on the value of rotor resistance (Fig. Characteristics of AC Servo motor Torque-Speed Characteristics of AC Servo motor The rotating magnetic field interacts with these currents producing a torque on the rotor in the direction of field rotation. As the field sweeps over the rotor, e.m.f.s and hence the currents are induced in the rotor conductors forming a closed path. When two voltages with time phase difference of 90 electrical degrees are applied to the two stator phases 90 electrical degrees apart in space, a rotating magnetic field is produced. The principle of operation of ac servo motor is same as that of an ordinary two-phase induction motor. AC servo motors have small air gaps to reduce magnetizing current and consequent losses. This also provides corresponding increase in torque. To minimize rotor kinetic energy, servo motors are wound with as many poles as possible so that they operate at low speeds. 2: Cross-section of a two-phase servo motor with drag-cup type rotor. The slotted rotor laminations are replaced by a set of stationary ring shaped laminations that provide a low-reluctance path for the magnetic flux.įig. This type of rotor is a special form of squirrel-cage rotor in which conductors are in the form of a drag-cup made of a non-magnetic conducting material such as copper, aluminium, or an alloy. The inertia of the rotor is further reduced using drag-cup rotor (Fig. It has high resistance in order to obtain a torque-speed characteristic as linear as possible. ![]() The rotor is usually of the squirrel cage type with small diameter and large length to keep the mechanical inertia as low as possible. This control voltage is supplied from a servo amplifier. The other winding called the control winding (or control phase) is energised by the variable control voltage which is 90 electrical degrees out of phase with respect to the voltage across the main winding. One of the windings called the main winding (also called as reference or fixed phase) is excited from the constant-voltage supply source. The stator of this motor which has a laminated structure, is wound with its two windings placed 90 electrical degrees apart in space. Similar to a normal induction motor, this motor comprises of a stator and a rotor. 1 represents the circuit diagram of AC servo motor.įig. Most of the servo motors used in servomechanisms are ac and AC servo motors are of the two-phase induction motor type. In this topic, you study AC Servo motor – Working Principle, Circuit Diagram, Construction, Characteristics & Applications. ![]()
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