AC servo motor:
There are some special applications of electrical motor where rotation of the motor is required for just a certain angle and not continuously for long period of time. For these applications some special types of motor are required with some special arrangement which makes the motor to rotate a certain angle for a given electrical input (signal). Such motors can be ac or dc motors. These motors are used for position control or in servo mechanisms, hence are termed as servomotors.
The AC servomotor consists of main and control winding and squirrel cage / drag cup type rotors. These two windings are placed with 90° displacement in space. The reference voltage Vr is applied to the main or reference winding while the control voltage Vc is applied to control winding which controls the torque-speed characteristics. The rotor is squirrel cage with longer length and small diameter.
The rotor has high resistance to increase starting torque and linear torque speed characteristics. The 90 degree space displacement of the two coils/windings and the 90 degree phase difference between the voltages applied to them result in production of rotating magnetic field in the air gap.
This rotating magnetic field is cut by rotor conductors & the emf is induced in them, which circulates current through them. According to the basic motor principle, force is exerted on the current carrying conductors when they are in the magnetic field. Thus the force or torque is exerted on rotor and is set in motion.
Applications :
1. Process control equipment.
2. Machine tools.
3. Robotics.
4. Process Controllers.
5. AC position control applications.
6. Portable drilling machine.
7. Sewing machine.
8. CNC machines.
9. Robotic hands.
10. Conveyers which require precise control
11. Fluid dispensing machines
12. Precision instruments such as camera, printers
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