Calculator Inputs
Plotly Graph
This curve shows estimated average DC voltage versus firing angle for the selected rectifier family and electrical inputs.
Example Data Table
| Case | Rectifier | Control | VLL (V) | α (°) | R (Ω) | Estimated VDC (V) | Estimated IDC (A) | Ripple (Hz) |
|---|---|---|---|---|---|---|---|---|
| 1 | Bridge 6-pulse | Diode | 400 | 0 | 20 | ≈ 539.10 | ≈ 26.96 | 300 |
| 2 | Bridge 6-pulse | SCR | 415 | 30 | 25 | ≈ 483.72 | ≈ 19.35 | 300 |
| 3 | Half wave 3-pulse | Diode | 400 | 0 | 15 | ≈ 268.62 | ≈ 17.91 | 150 |
Formula Used
Phase voltage: Vphase = VLL / √3
This converts the given line-to-line RMS voltage into phase RMS voltage.
Ideal bridge average DC voltage: VDC,ideal = 1.35 × VLL × cos(α)
For an uncontrolled bridge, α = 0°, so cos(α) = 1.
Ideal half wave average DC voltage: VDC,ideal = 0.675 × VLL × cos(α)
This is the three phase half wave average model under ideal conditions.
Commutation factor: Kcomm = (p / 2π) × ω × Ls
Here p is pulse number, ω = 2πf, and Ls is source inductance in henry.
Corrected average DC voltage: VDC = (VDC,ideal − nVdrop) / (1 + Kcomm / R)
n equals 2 for bridge conduction paths and 1 for half wave paths.
DC current and power: IDC = VDC / R, PDC = VDC × IDC
These results assume the entered resistance is the effective DC load resistance.
Ripple frequency: fripple = p × fsupply
Six-pulse circuits ripple at six times supply frequency. Three-pulse circuits ripple at three times supply frequency.
This calculator is an engineering estimate. It focuses on average DC behavior, practical voltage drops, and ripple frequency. It does not replace detailed harmonic, thermal, or transient design studies.
How to Use This Calculator
- Select the rectifier family: bridge or half wave.
- Choose uncontrolled diode mode or controlled SCR mode.
- Enter the line-to-line RMS voltage and supply frequency.
- Enter the firing angle only when using controlled operation.
- Provide load resistance, source inductance, and device drop values.
- Press the calculate button to show results above the form.
- Review the graph, result cards, and engineering estimates.
- Download the result summary as CSV or PDF when needed.
Frequently Asked Questions
1. What does this calculator estimate?
It estimates average DC voltage, DC current, load power, ripple frequency, PIV, device drop, and commutation drop for common three phase rectifier configurations.
2. What is the difference between bridge and half wave rectifiers?
A bridge rectifier is a six-pulse circuit with higher average DC output and lower ripple. A half wave rectifier is a three-pulse circuit with lower output and stronger ripple.
3. Why does firing angle reduce output voltage?
In controlled rectifiers, delayed triggering shortens the effective conduction interval contributing to DC output. As firing angle rises, the cosine term reduces the average DC voltage.
4. What is PIV in this tool?
PIV means peak inverse voltage. It is the reverse voltage stress that a non-conducting device may need to withstand during operation.
5. Why include source inductance?
Source inductance introduces commutation overlap and reduces the usable average DC voltage. This calculator applies a practical average-model correction using the entered inductance value.
6. Does this replace a harmonic study?
No. It is a fast design calculator. Harmonics, transformer details, thermal limits, device selection, and control dynamics still need detailed engineering analysis.
7. Can I use this for diode and SCR systems?
Yes. Choose uncontrolled mode for diode rectifiers and controlled mode for SCR rectifiers. The firing angle becomes active only for controlled operation.
8. Why are my results approximate?
Real systems include transformer impedance, non-ideal waveforms, discontinuous current, temperature effects, and switching behavior. This page uses standard average-value relations for quick engineering estimates.