Consider an ideal full-bridge single-phase DC-AC inverter with a DC bus voltage magnitude of 1000 V. The inverter output voltage v(t) shown below, is obtained when diagonal switches of the inverter are switched with 50% duty cycle. The inverter feeds a load with a sinusoidal current given by, i(t)=10sin(ωt-π/3), where ω=2π/t. The active power, in watts, delivered to the load is _____. (round off to nearest integer)
Correct Answer :
Solution :
The correct answer is 3183.
1. Analysis of the Output Voltage Waveform:
From the given waveform of the output voltage , we observe that it is a symmetric square wave with a period of and a peak magnitude equal to the DC bus voltage .
The voltage waveform can be mathematically represented over one cycle as:
2. Fourier Series Expansion of the Voltage:
For a square wave with odd symmetry, the Fourier series expansion consists only of odd harmonic sine terms:
The fundamental frequency component () of the output voltage is:
Substituting :
3. Load Current and Active Power Calculation:
The current delivered to the load is purely sinusoidal at the fundamental frequency:
Since the load current has no higher-order harmonics, active power is only delivered by the fundamental component of the voltage. The active power is given by:
where:
- The RMS value of the fundamental voltage is
- The RMS value of the load current is
- The phase angle difference is
Substitute these values into the power equation:
Since :
Evaluating this numerically:
Rounding to the nearest integer, we get:
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