Specifications of feed positioning system:


  1. Accuracy of feed positioning system = 2 arc min. from the dish vertex
  2. Resolution = 1 arc min.
  3. Drive specifications :
    1. Half Hp DC servo motor
      1. Speed : 2000 RPM
      2. Torque : 2.7 N-m
      3. Operating Voltage : 55 Volts
      4. Weight : 11kg
      5. Inertia : 2.2 kg sqm X 10 ˆ (-3)
      6. Thermal time constant: 23 min.
      7. Electrical time constant : 2 milliseconds
      8. Mechanical Time constant : 14.7 millisec.
      9. Torque constant : 0.24 N-m/A
      10. Inductance : 1.1 mH
      11. Armature Resistance : 0.62 ohm
      12. Peak current : 100 amp.
      13. Voltage constant : 25V per 1000 rpm
    2. Tachometer :
      1. 4V/1000 rpm
      2. Ripple : 1.5% at 400 rpm
      3. Inertia : 8.4 X 10 ˆ (-5) kg-sqm
      4. Weight : 0.32 Kg
    3. Brake :
      1. Holding torque : 13 N-m
      2. Rated voltage to be applied for releasing brakes :24 VDC
      3. Coil current : 1 Amp
  4. Feed Drive Controller
    1. Encoder : Incremental encoder with one arc min. resolution
    2. Speed profile : Trapezoidal
    3. Speed control : PWM technique at 10 KHz.
    4. Power drive : 'H' Configuration using IRF150 MOSFETS.
    5. PWM Generation : 8051FA microcontroller with non volatile memory to retain current position and enabling Liquid crystal display. Microcontroller communicates with Antenna Base Computer using RS-485 protocol with an asynchronous link.



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