Basics of AC Servo

  •  A “servo system” is a generic term used for an automatic control system. In other words a mechanism which adjusts itself during continued operation through feedback.
  •  Servo control is a closed loop control system for electric motors. The servo system uses a sensor to sense motor position/speed. Servo control has a feedback circuit which changes the drive power going to motor according the control input signals and the feedback signals from sensors
  • Three basic types of servo motors are used in modern servo systems: ac servo motors, based on induction motor designs; dc servo motors, based on dc motor designs; and ac brush less servo motors, based on synchronous motor designs.
  • AC servomotors are typically permanent magnet synchronous motors that often have low torque-to-inertia ratios for high acceleration ratings.
  • AC servomotors use integral encoders, integral resolvers, and integral tachometers for feedback signals.
  •  Integral encoders contain attached encoders for angular position signals, and may include absolute or incremental encoders and a number of different encoder signal types.
  • Integral resolvers contain an attached resolver to indicate the angular  position.Resolvers often rely on magnetic fields and are typically very robust; they are sometimes specified for harsh environments.
  •          Integral tachometers produce an output indicating rotational motor speeds
Why it is used?
  •  When a motion control system requires greater acceleration and velocity with high positioning than a servomotor is a better choice. Servomotors can accelerate faster because they have a smaller diameter, lower inertia rotors.
  •  1 HP AC servomotor, for instance, accelerates two times faster than a vector motor when considering inertia only. However, when the additional starting or acceleration torque capability of the AC servomotor is considered, then the DC servomotor accelerates three or more times faster.
·         In a servo system the encoder gives the motors position to the servo amplifier and it compares this with the desired position to get the error. The amplifier then sends current to the servo motor to make the motor move into the proper position, reducing the error. The servo’s resolution is based on the encoder attached to it, and the servo amplifier’s error. A servo is a motor that can be stopped anywhere you want it, with no “detents” either needed or present. You can turn it to any position you like (within its range, of course), and assuming it’s been properly “dialed in”, it’s reasonable to expect that when you say “turn to 4.6 degrees” and punch the “go” button, it’s going to turn whatever it controls to point at a reasonable approximation of 4.6 degrees.

  • Index Tables
  • Opening/ Closing Doors.
  • Diamond cutting machine.
  • Packing/Wrapping Machine.
  • Food Processing Machine.
  • Semiconductor manufacturing Equipment.
  • Belt Driven machine.
  • SMT machine.
  • General Automation Machines.
  • X-Y Robots.
  • Constant rate of feeding, where a fixed operation is required.

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