The output voltage of a single-phase full bridge voltage source invert...
Waveform for output voltage of single phase full bridge PWM inverter


V
o1rms = fundamental r
ms output voltage

Given, V
o1 = 0.754 V
dc 

Pulse width = 2d = 112.88
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The output voltage of a single-phase full bridge voltage source invert...
Given data:
- Type of inverter: Single-phase full bridge voltage source inverter
- PWM technique: Unipolar PWM with one pulse per half cycle
- Desired fundamental rms component of output voltage: 75% of DC voltage
To find: The required pulse width in degrees for achieving the desired output voltage
Solution approach:
- We need to determine the pulse width of the gating signal that controls the switching of the inverter devices.
- Since it is a single-phase full bridge inverter, there are four switching devices (two in the upper arm and two in the lower arm) that are controlled by the gating signal.
- The gating signal is generated using PWM technique, which means that the pulse width of the signal is varied to achieve the desired output voltage.
- In unipolar PWM with one pulse per half cycle, the gating signal has only one pulse per half cycle, which means that the pulse width is varied between 0 and 180 degrees.
Calculation steps:
1. Let the DC voltage be Vdc.
2. The peak value of the fundamental rms component of output voltage is given by:
Vp = Vdc * 0.75
3. The peak value of the gating signal is equal to the peak value of the output voltage, which is:
Vg = Vp
4. The average value of the gating signal is given by:
Vavg = (1/2π) * ∫(0 to π) Vg * sin(ωt) dt
where ω is the angular frequency of the gating signal.
5. Simplifying the above equation, we get:
Vavg = (2/π) * Vp
6. The duty cycle of the gating signal is defined as the ratio of pulse width to the period of the gating signal. In unipolar PWM with one pulse per half cycle, the period is equal to half cycle time, which is:
T = (1/f) * π
where f is the frequency of the gating signal.
7. The duty cycle is given by:
D = (Pw/T) * 100%
where Pw is the pulse width of the gating signal.
8. Equating the average value of the gating signal to the desired value of the fundamental rms component of output voltage, we get:
Vavg = (2/π) * Vp = 0.75 * Vdc
9. Substituting Vp = Vg and simplifying, we get:
D = (360/π) * 0.75 ≈ 112.88 degrees (rounded off to one decimal place)
Therefore, the required pulse width in degrees for achieving the desired output voltage is approximately 112.88 degrees.