How Avr works in a generator ?

When the engine rotates the generator, the rotor produces an AC voltage in the excitation winding. This AC voltage is converted into DC using a rectifier and capacitor.

The AVR continuously checks the output voltage of the generator. If the voltage is low, the AVR turns ON the transistor, allowing more current to flow into the field winding, which increases the output voltage.

How to install avr in generator
Ep6500 Honda Avr

If the voltage becomes too high, the AVR turns the transistor OFF. Even when the transistor is OFF, the field current does not stop suddenly; it safely flows through a diode, preventing damage to components.

By rapidly switching the transistor ON and OFF (duty cycle control), the AVR maintains a stable output voltage.

Some generators use a small permanent magnet in the rotor to ensure that a minimum voltage is always available for excitation

G-avr for dynamo voltage regulators

A standard 4-wire universal AVR has:

  1. Two sensing / supply wires (AC input)

    • Often marked: AC / ~ / S / Input

    • Connected to generator stator output

    • Provides power and voltage feedback to the AVR

  2. Two field wires (DC output)

    • Often marked: F+ / F- / + / –

    • Connected to rotor field winding via slip rings

 Never confuse sensing wires with field wires — this is the most common mistake.

  Identify Generator Terminals

Before wiring, identify these on your generator:

A) Stator Output (AC)

  • Usually labeled:

    • L – N

    • R – S

    • 220V / 110V output

  • Use a multimeter to confirm AC voltage when generator runs

B) Rotor Field Wires

  • Two wires coming from slip rings

  • Low resistance (typically 10–50 Ω)

  • These go directly to the AVR field output

Step 1: Power Off

  • Engine must be OFF

  • Remove and disconnect the old AVR completely

Step 2: Connect AC Sensing Wires

  • Connect the AVR AC input wires to generator output L and N

  • For 220V systems, connect across the full output

  • For dual-voltage generators, use the high-voltage terminals

Step 3: Connect Field Wires

  • Connect AVR F+ and F- to the rotor slip rings

  • Ensure tight and clean connections

Step 4: Set AVR Voltage Adjustment

  • Turn the AVR voltage adjustment potentiometer fully anticlockwise

  • This prevents over-voltage during first startup

Step 5: Start the Generator

  • Run the generator at rated speed (1500 or 1800 RPM)

  • Slowly rotate the AVR voltage adjustment clockwise

  • Stop when rated voltage appears (110V or 220V)

5. If Voltage Does Not Build Up

Check the following:

  • Reverse the F+ and F- connections

  • Increase engine speed

  • Check residual magnetism

  • Flash the field with 12V DC for 1 to 2 seconds

  • Verify AC voltage at the AVR input terminals

6. Common Wiring Mistakes

  • Connecting field wires to stator output

  • Supplying AVR from incorrect voltage tap

  • Running generator below rated RPM

  • Adjusting AVR before engine stabilizes

  • Using incorrect AVR voltage rating

7. Typical Applications

  • Petrol and diesel generators

  • Brush-type alternators

  • Single-phase self-excited generators

  • Industrial and rental generator sets