A stator and a rotor composed of the A.c. Servo motor. The two windings, existed in the stator, uniformly distributed and displaced by 90o in space, from each other.
The construction of winding is called as main winding or fixed winding or reference winding. A constant voltage a.c. supply plays as a power to excite the reference winding.
The other winding is called as control winding to be excited by variable control voltage, which is obtained from a servo amplifier. With respect to the voltage applied to the reference winding, control voltage is 90o out of phase and the winding are 90o away from each other. To obtain rotating magnetic field is a necessity.
The schematic stator is shown in the Fig. 1.
Fig. 1 Stator of a.c. servomotor
For reducing the loading on the amplifier, using a tuning capacitor in parallel with the control winding to increase the impedance of the control is a good method.
The Stator Construction of AC Servo Motor:
This diagram shows the stator’s construction: The A.c. servo motor is basically a two phase induction motor with some special design features. The two pole-pairs (A-B and C-D) making up of the stator mounted on the inner periphery of the stator, such that 90°is their axes’ angle. Each pole-pair carries a winding. A phase displacement of 90°should be included in the exciting current. The single phase is used to drive the motor, and so to produce a phase difference of 90°, a phase advancing capacitor is connected to one of the phase. The stator construction of AC servo motor are shown in diagram.
About the rotor’s working: Squirrel cage or drag-cup type are the basic parts of the rotor construction, which is shown in the following diagram. Laminations consists of the squirrel cage rotor. The rotor bars are placed on the slots and short circuited at both ends by end rings. For reducing inertia and obtaining food accelerating features, the diameter of the rotor is kept small. Every part has a great impact on the Ac servo motor’s working.