Enter the AC input voltage (RMS) into the calculator to estimate the DC link voltage (ideal diode bridge with a large DC link capacitor).

DC Link Voltage Calculator

Enter one value to calculate the other.

Note: This uses VDC ≈ √2 · VAC,rms (peak of the AC). In real circuits, diode drops and load/ripple reduce the DC link voltage.

DC Link Voltage Formula

The following formula is commonly used to estimate DC link voltage for an ideal diode bridge feeding a large DC link capacitor, given the AC input RMS voltage (line-to-line RMS for a 3-phase source).

V_{DC} \approx \sqrt{2}\,V_{LL,\mathrm{rms}}

Variables:

  • (V_{DC}) is the DC link voltage (approximate, ideal)
  • (V_{LL,rms}) is the AC input line-to-line RMS voltage (for a 3-phase source)
  • (\sqrt{2}) is the square root of 2 (approximately 1.414)

To estimate the DC link voltage, multiply the AC input RMS voltage by \(\sqrt{2}\) (i.e., convert RMS to peak). If you already have the peak line-to-line AC voltage, then (ideally) \(V_{DC}\approx V_{LL,peak}\). In practice, diode drops and load/ripple will reduce the measured DC link voltage.

What is DC Link Voltage?

DC link voltage is the voltage present across the DC link capacitor in a power electronic converter. This voltage is crucial for the operation of various types of converters, including inverters and rectifiers. The DC link voltage is typically derived from an AC source and is used to provide a DC bus for the converter’s operation. Proper calculation and control of the DC link voltage are essential for the efficient and reliable performance of power electronic systems.

How to Calculate DC Link Voltage?

The following steps outline how to calculate the DC Link Voltage.

  1. First, determine the AC input RMS voltage (use line-to-line RMS for a 3-phase source), \(V_{LL,rms}\).
  2. Next, use the formula \(V_{DC} \approx \sqrt{2}\,V_{LL,rms}\) to estimate the DC link voltage (ideal diode bridge with a large capacitor).
  3. Finally, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

AC Input Voltage (line-to-line RMS), \(V_{LL,rms}\) = 100 V

Using the formula, the DC Link Voltage \((V_{DC})\) can be estimated as follows:

V_{DC} \approx \sqrt{2}\cdot 100 \approx 141.42\,\text{V}