EE-303 (Compact Microcontroller AVR)

Automatic Voltage Regulating Relay : EE-303

Emco Electronics’ Microcontroller based Automatic Voltage Regulating Relay type EE–303 is a new generation Relay used for regulating the secondary voltage of Power Transformers with a motor driven On Load Tap Changer (OLTC).

A single control pulse to the motor causes a change in voltage by one step. When step by step function is inactive, the motor drive is controlled by a continuous control pulse.

A “Raise” or “Lower” control signal is generated by the voltage regulator when the measured voltage deviates from preset conditions.

The parameters are programmable through a front panel keyboard and are stored in NonVolatile Memory.


  • Microcontroller based architecture
  • Built-in Tap Position Indicator upto 35 Taps
  • Readout of Primary, Secondary Voltages and Tap No.
  • Keyboard programmable parameters
  • Independent Lower, Raise and Nominal value settings
  • Linear or Inverse Time response
  • Blocking for UV, OV, CF & Max, Min Tap No.
  • Auto-Manual mode of operation
  • Test mode for testing AVR
  • Minimum and Maximum PT Voltage display
  • Single pulse or continuous pulse operation
  • Tap Changer Counter
  • AVR Disable mode for remote operation


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