Rectifed 3 Phase

[larryg]

If you run a 3phase source through a fullwave bridge, what DC values of voltage and current would you get? Use 120 VAC, Delta as an example. I've been getting confused about the sqrt of 2 and 3.

Thanks

 

[jbartos]

Suggestion: Reference:
1. Bedford B. D., Hoft R. G., "Principle of Inverter Circuits," John Wiley & Sons, Inc., New York, 1964
Reference 1 Page 68 Figure 3.6 shows DC value of 3-phase voltage as
Ed=(3 x 3**0.5 x E1-n,m)/(PI)
which for 120V is:
Ed=(3 x 3**0.5 x 2**0.5 x 120)/3.14=280.7VDC

 

[stevenal]

Current depends on the load. Voltage can be calculated. Divide by root 3 to find line to neutral voltage given line to line. Multiply by root two to find peak voltage of a sinusoid given the rms value. Looks like you will need both factors. Start by drawing the output waveform. Then square, integrate, divide by the period, and take the square root to find rms of the output. Usual assumption is that diodes are ideal.

 

[stevenal]

Correction: Since load is connected line to line, forget about the root 3 factor.
Using Mathcad, I came up with 162.2 Vrms.

 

[jbartos]

280.7 Vrms/1.73=162.254 Vrms is correct for 120 V phase to phase. It is understood that 120 V is phase to neutral in 3-phase 208V/120V system that is a very common and standard 3-phase voltage system. E1-n,m is a line to neutral max voltage with respect to the cited Reference Figure.