Electrical Engineering Virtual Power Lab Experiments

Determination of Positive, Negative and Zero Sequence Reactances of an Alternator

Procedure

A. Determination of Positive Sequence Reactance (X₁)

  1. Make connections as per the circuit diagram.

  2. Drive the alternator at rated speed using the prime mover.

  3. Keep the field winding open-circuited.

  4. Apply a balanced three-phase voltage to the stator.

  5. Increase the voltage gradually until rated current flows.

  6. Note the line voltage and current.

  7. Calculate the phase voltage and phase current.

  8. Determine:

    X₁ = Vph / Iph

B. Determination of Negative Sequence Reactance (X₂)

  1. Maintain rated speed of the alternator.

  2. Interchange any two stator phase connections.

  3. Keep the field winding open.

  4. Apply a balanced three-phase supply.

  5. Increase the voltage gradually.

  6. Record voltage and current readings at rated current.

  7. Calculate:

    X₂ = Vph / Iph

C. Determination of Zero Sequence Reactance (X₀)

  1. Connect the three stator phase windings in series.

  2. Keep the rotor stationary and field winding open.

  3. Apply a low single-phase AC voltage.

  4. Increase the voltage slowly until rated current flows.

  5. Record voltage and current.

  6. Calculate:

    X₀ = V / 3I

Observations

Table 1 - Open Circuit Test

S.No. Voltage (V) Field Current (A) Speed (rpm)
1. . . .
2. . . .
3. . . .
. . . .
. . . .
n . . .

Table 2 - Short Circuit Test

S.No. Armature Current (A) Field Current (A) Speed (rpm)
1. . . .
2. . . .
3. . . .
. . . .
. . . .
n . . .

Table 3 - Determination of X₂

S.No. Voltage (V) Current (A) Power (W) Z₂ (Ω) X₂ (Ω)
1. . . . . .
2. . . . . .
3. . . . . .
. . . . . .
. . . . . .
n . . . . .

Table 4 - Determination of X₀

S.No. Voltage (V) Current (A) Speed (rpm) X₀ (Ω)
1. . . . .
2. . . . .
3. . . . .
. . . . .
. . . . .
n . . . .

Video for experiment:




Experiment 3. To determine positive sequence, negative sequence and zero sequence reactances of an alternator.
Video-2