Rectified AC Power

[XDFreakLP]

Hello all!

I am currently working on a Multipurpose Transformer Power Supply. I have a couple of pretty beefy Transformers at my disposal, but while i was installing them on my Top-Hat-Rails and connected them to my Rectifier board i came across something that confused me.

One of my Transformers can supply 36V at 4.5A. When i connect my Rectifier to the Transformer, the DC output voltage is around 50V.
I am wondering if the Transformer can still supply 4.5A at this voltage, or if the current is decreased (As i think it'd have to, otherwise i would've created an overunity machine). I was wondering if any of you guys could give me some infos on this topic.

 

[hevans1944]

The 36 V output is the rms (root mean square) voltage of a sine wave. An AC sinusoid with X rms volts has the same heating effect on a pure resistive load as X DC volts.

The peak voltage of a sinusoid, which is what a rectifier would charge a capacitor to, is the square root of two times the rms voltage: 1.414 x 36 V = 50 V (about). This will decrease to a lower average value when you try to draw DC from the rectified AC by applying a resistive load. The DC will also have a saw-tooth shaped "ripple" at either the power line frequency (half-wave rectifier) or twice the power line frequency (full-wave rectifier). In any case, the maximum power you should draw from the transformer is 36 V x 4.5 A = 162 watts.

So, no, the transformer cannot supply 4.5 A at 50 V without exceeding its ratings.

 

[HellasTechn]

If you use a multimeter to obtain readings you have to remember that multimeters in AC mode will read RMS voltages.
The difference in the measured AC voltage is because you measure the RMS value of it. The pick to pick value is higher so when you convert AC to DC through a bridge rectifier it is still the same but when you add a filter capacitor then the formerly pulsating "DC" voltage level will almost match the AC pick to pick voltage level so with your multimeter you will see a higher value.

I hope that helps

 

[Harald Kapp]

Here's some stuff with images:
https://en.wikipedia.org/wiki/Rectifier
http://www.electronics-tutorials.ws/diode/diode_6.html