Why is the output voltage of a rectifier always greater than input voltage..connecting a low pass filter also increases the voltage furthermore

 

Your meter may be reading the peak voltage of your output when measuring DC voltages. The peak voltage of a sine wave is about 1.4 times the RMS voltage.

The filter capacitor charges to the peak voltage. Your meter will read the peak voltage when set to DC volts.

 

Your meter may be reading the peak voltage of your output when measuring DC voltages. The peak voltage of a sine wave is about 1.4 times the RMS voltage.

The filter capacitor charges to the peak voltage. Your meter will read the peak voltage when set to DC volts.

so why does the peak voltage at the output of the rectifier vary with the peak voltage on the capacitor like u said

 

AC voltages are specified by RMS values.
The amplitude of the sine wave is the RMS value multiplied by the square root of 2.

When the AC signal is rectified, there is still a huge ripple voltage even though it is DC. What your volt meter will indicate will depend on the design of the voltmeter.

When a capacitor is charged with the rectified DC voltage the capacitor will tend to hold the voltage at the peak voltage. If the charge is allowed to discharge through a load attached to the capacitor then the voltage will fall in between the peak cycles. Hence you will measure a lower average voltage depending on the value of the capacitance and the value of the load.

 

AC voltages are specified by RMS values.
The amplitude of the sine wave is the RMS value multiplied by the square root of 2.

When the AC signal is rectified, there is still a huge ripple voltage even though it is DC. What your volt meter will indicate will depend on the design of the voltmeter.

When a capacitor is charged with the rectified DC voltage the capacitor will tend to hold the voltage at the peak voltage. If the charge is allowed to discharge through a load attached to the capacitor then the voltage will fall in between the peak cycles. Hence you will measure a lower average voltage depending on the value of the capacitance and the value of the load.

So is the peak voltage dependent on the capacitance of the capacitor..let me just list the breakdown..220v in - 33v out(transformer secondary) - 40v (rectifier out) - 48v (low pass filter)

 

It is hard to know what is going on without a schematic.
What you should be seeing according to the description is:

33 VAC(RMS) * 1.414 = 46.67 VAC(peak)
Allow for some drop in the diodes (say 1.4V) gives 46.67 VAC(peak) - 1.4 = 45.26 VDC (with a bit of ripple)​

You did not say if the filter is a passive filter or an active filter.
In truth, I've never seen an active filter at the output of a power supply.

 

So is the peak voltage dependent on the capacitance of the capacitor.

Not significantly.
But the drop of the capacitor voltage with an output load will depend upon the capacitance.

To really measure these voltages properly you need an oscilloscope.

 

so why does the peak voltage at the output of the rectifier vary with the peak voltage on the capacitor like u said

The peak voltage will always be the same to a great degree, with a capacitor on the bridge output, the mean level will depend on load.
The peak to peak voltage will not be maintained if the capacitor is drained off between peaks.
Max.

 

The peak voltage will always be the same to a great degree, with a capacitor on the bridge output, the mean level will depend on load.
The peak to peak voltage will not be maintained if the capacitor is drained off between peaks.
Max.

Here's a chart of this that I plotted some years ago. It shows how, as C increases, the time-average voltage after a rectifier-plus-filter-cap increases for a given load R.

The blue line shows the lower limit, which is the time-average voltage factor for a sine wave, ~0.635. That's what you get if the cap is too small to really do anything. The black line is the upper limit, the peak of the sine wave. That's what you get with low load (= high R) and a big C.

The red line shows what you get at points in between. It's the time-weighted average, which is to necessarily what you will see from a typical cheap meter.



edit - the x-axis is the RC time constant of the filter cap C and load R, times the frequency.