Out put Voltage of Bridge Ractifire

Assuming that the 100 V, 1 ph, you state is the RMS value, then the output will be 100 V minus voltage drop across the rectifier. Each phase of a 100 V, 3 phase source will produce the same voltage as single phase, but the three tied together will produce less ripple current.

Just a question....

The peak voltage would stay the same if it is 1Φ or 3 Φ, but would not the RMS value increase if the 3 Φ voltages are combined into a single 12 pulse DC voltage? This would effectively fill in the hollows in the single phase pulsating DC giving a higher RMS value making it much closer to flat DC.

Cheers, element

It was an attempt to keep it simple . . .

The RMS value of the rectified and unfiltered voltages (1 ph and 3 ph) are slightly different for the reason you point out. Properly sized and filtered (capacitors) power supplies made from either source will have roughly the same voltage whether single or 3 phase.

Uh, way back in active devices 1 we were taught that the output of a bridge rectifier depends not only on the input voltage but also the load. Is there a capacitor filter? What is the load resistance? Oh yes, what frequency are you working at? In other words this is not a simple question to be answered in a line or two...

The output voltage peak value is equal to the input peak value minus the rectifier drop (two diode drops). After the rectifier you typically use some capacitance to store charge until the next peak value occurs in the incoming AC source voltage. The load will draw Power from the storage capacitance while the incoming AC signal is reversing polarity and the rectifier is blocking. The min value of the output voltage will depend on the load and the capacitance; the voltage change on the capacitor is equal to the load current multiplied by the time it draws from the capacitor and divided by the total capacitance or dVc = I * dt / C. Parasitics and ESR will effect the final values also. A single phase AC peak value is approximately 1.414 * the RMS value (true for sine waves only)

Do:

• Build the single phase bridge rectifier: four diodes V over 250 V I(current) over required DC load amps
• Assembly testing station: Input -autotransformer 120V /0-120 V + Your Bridge + Voltmeter & DC Load
• If your load requires DC voltage with v. low ripples add Capacitor parallel to DC Bridge output (which is parallel to the load). The level of ripples can be observed on the Oscilloscope (add it if necessary)
• For three-phase AC Input voltage better find a diagram for the rectifier and assembly it, than use full testing station with o-scope, voltmeter and ampere-meter.

Above is the way to understand the phenomenon of practical application of AC/DC converter (rectifier). Can you understand physics just a reading books? If Yes Search Internet for Rectifier Diagrams