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SURGE TESTER - CALIBRATION
There are two procedures for doing the calibration of Surge Tester:
  1. Any Standard 50MHz or above Oscilloscope and X1000 times, 10KV AC Probe.
  2. Any Standard 50MHz or above Oscilloscope and X10 times AC Probe.
Pre-requisites for Calibration:
  • Calibrated Oscilloscope (Min 50MHz)
  • A balanced 3φ stator or two 1φ balanced coils


  • NOTE: The Oscilloscope can also be calibrated using a square wave generator having a rise time of 0.1 micro sec, min. output voltage of 100 volts (peak-to-peak) and frequency of oscillation of 1KHz.
     
    The circuit diagram shown below gives an overview of a basic Surge Tester and the significance of each component in the circuit. The user should have this basic knowledge before performing the calibration.



    Circuit Components Description
    Vc Supply Voltage Source 230V/50Hz
    Ds Half Wave Rectifier
    Rs Charging Current Limiting Resistance
    Ts Discharge Switch
    Rc Surge Discharging Current Limiting Resistance
    C Charging Capacitor
    Lc Coil under Test
    Cp High Voltage Pick-up Capacitor
    Ca & Rx Attenuation Capacitor & Resistance

     

    OPTION I (X1000 times Probe):
    1. Connect the Surge Test leads to the Stator or coils.
    2. Set the Test Select switch to Position A for 3φ winding or Position 1φ for 1-phase coils.
    3. Make sure the Surge tester is connected to a constant voltage source with 230V/50Hz.
    4. Set the Test voltage control to zero.
    5. Set the VOLTS/DIV to 500 position on the Surge Tester.
    6. Set the VOLTS/DIV to 0.5 V on the Oscilloscope. As we are using X1000 times probe it will be equivalent to 500 volts.
    7. Connect the X1000 Oscilloscope probe to the RED test lead and Ground clip of the probe to the Ground Test Lead.
    8. Now slowly increase the Surge test voltage so that the charging peak of waveform equals (exact) one vertical divison on the oscilloscope. The waveform on the Oscilloscope will be Inverted wrt to display on Surge tester.
    9. Verify that the waveform also shows one vertical divison on the CRT display of Surge tester.
    10. If there is a discrepancy between the peak amplitude of two waveforms then surge test waveform can be calibrated by adjusting the value of Attenuation Capacitance connected to the 500V/DIV switch internally.
    11. There are Individual Ca (Attenuation Capacitor) for each 500, 1000, 2000 & 4000 VOLTS/DIV therefore each range has to be calibrated wrt oscilloscope. The procedure remains the same as mentioned above.
     


    OPTION II (X10 times Probe):
    1. Connect the Surge Test leads to the Stator or coils.
    2. Set the Test Select switch to Position A for 3φ winding or Position 1φ for 1-phase coils.
    3. Make sure the Surge tester is connected to a constant voltage source with 230V/50Hz.
    4. Set the Test voltage control to zero.
    5. Set the VOLTS/DIV to 500 position on the Surge Tester.
    6. Connect the X1000 Oscilloscope probe to the RED test lead and Ground clip of the probe to the Ground Test Lead.
    7. Now slowly increase the Surge test voltage so that the charging peak of waveform equals (exact) to 500 volts on the oscilloscope. The waveform on the Oscilloscope will be Inverted wrt to display on Surge tester.
    8. Make sure you disconnect the probe of the oscilloscope from the Surge test leads. This is X10 probe, the high voltage may damage the probe and the scope.
    9. Verify that the waveform also shows one vertical divison on the CRT display of Surge tester.
    10. If there is a discrepancy between the peak amplitude of two waveforms then surge test waveform can be calibrated by adjusting the value of Attenuation Capacitance connected to the 500V/DIV switch internally.
    11. Once the 500V/DIV is calibrated, slowly increase the Surge test voltage so that it shows Two vertical divisons on the display. Now press the 1000V/DIV switch, the amplitude should drop to exact one division.
    12. If there is any discrepancy adjust the Attenuation Capacitor for 1000 position internally.
    13. Once the 1000V/DIV is calibrated, slowly increase the Surge test voltage so that it shows Two vertical divisons on the display. Now press the 2000V/DIV switch, the amplitude should drop to exact one division.
    14. If there is any discrepancy adjust the Attenuation Capacitor for 2000 position internally.
    15. Once the 2000V/DIV is calibrated, slowly increase the Surge test voltage so that it shows Two vertical divisons on the display. Now press the 4000V/DIV switch, the amplitude should drop to exact one division.
    16. If there is any discrepancy adjust the Attenuation Capacitor for 4000 position internally.




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