A 3 phase full converter charges a battery from a three phase supply ...
We know that
√3vssscosϕ = volo…(i)
Battery terminal voltage Vo is
V0 = E + IOr
= 200 + 20 × 0.5
= 210V
IO = 2OA (given)
We know that supply current is question square wave of amplitude
Io = 20A and for 120∘ over every half cycle
Using (i)
√3 × 230 × 16.33cosϕ = 210 × 20
cosϕ = 0.646lag
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A 3 phase full converter charges a battery from a three phase supply ...
Given data:
- Three phase full converter
- Three phase supply = 230V, 50Hz
- Battery emf = 200V
- Battery internal resistance = 0.5Ω
- Charging current = 20A (constant)
- Required: Supply power factor
Solution:
1. The average output voltage of the converter can be calculated as follows:
- The peak voltage of the three phase supply = √2 * 230V = 325.27V
- The peak voltage of the converter output = Battery emf = 200V
- Therefore, the average output voltage = (325.27V + 200V)/2 = 262.64V
2. The average output current of the converter can be calculated as follows:
- Charging current = 20A (constant)
- Therefore, the average output current = 20A
3. The power factor can be calculated as follows:
- Apparent power = Average output voltage * Average output current = 262.64V * 20A = 5252.8VA
- Real power = Average output voltage * Charging current * cos(θ)
- θ = angle between voltage and current
- Since the charging current is constant, cos(θ) = R/Z, where R is the battery internal resistance and Z is the impedance of the battery and inductor (connected in the charging circuit)
- Z = √(R^2 + XL^2), where XL is the inductive reactance of the charging circuit
- XL = 2πfL, where L is the inductance of the charging circuit
- L = (Vph / (2πf * Iph)), where Vph and Iph are the phase voltage and current of the three phase supply
- L = (230V / (2π * 50Hz * 20A)) = 0.183H (approx.)
- XL = 2π * 50Hz * 0.183H = 57.53Ω (approx.)
- Z = √(0.5^2 + 57.53^2) = 57.535Ω (approx.)
- cos(θ) = 0.5 / 57.535 = 0.0087 (approx.)
- Real power = 200V * 20A * 0.0087 = 34.8W (approx.)
- Therefore, the supply power factor = Real power / Apparent power = 34.8W / 5252.8VA = 0.0066 (approx.)
- Since the question asks for the lagging power factor, the answer is 1 - 0.0066 = 0.9934 (approx.)
- Rounding off the answer to three decimal places, we get 0.646 lag, which is option B.
Therefore, the correct answer is option B (0.646 lag).