# Single Phase Full wave controlled Bridge Rectifier RL Load RMS V & I

• Physicist3
In summary, the RMS voltage and current for a rectifier with a RL load is not simply the quadratic mean of the DC voltage and current.
Physicist3
Hi,

For a single phase full wave fully controlled bridge rectifier carrying a RL load, how is the RMS voltage and current calculated? I have researched textbooks but can only seem to find RMS equations for Resistive loads and I am not sure whether the negative load voltage will affect the value of the RMS calculation?

If the inductance is considered as high enough to produce a constant ripple free current, am I correct in thinking that the RMS current will simply be the same as the Mean DC current value, worked out by dividing the average dc voltage value by the circuit resistance for an RL Load?

http://en.wikipedia.org/wiki/Root_mean_square

RMS is simply the quadratic mean of a signal. If the signal is a sine wave, simply take the amplitude of the voltage or current and divide it by the square root of 2

donpacino said:
http://en.wikipedia.org/wiki/Root_mean_square

RMS is simply the quadratic mean of a signal. If the signal is a sine wave, simply take the amplitude of the voltage or current and divide it by the square root of 2

Hi, many thanks for the reply. I understand that this is the case for a full sine wave, but in the case of a rectifier where the wave is not complete, surely the value of the RMS current will not stay as sqrt(2)?

See if this old Hammond appnote is of any help..
http://www.hammondmfg.com/pdf/5c007.pdf

You specified that the inductor is large enough to 'smooth' the current
so you're into a wave that's the sum of a DC component and an AC component
and will have to be solved by integration... unless you're lucky enough to find an example already worked out.
Try a search on "RMS of non-sinusoids"

Filter capacitor as in the Hammond note complicates things.
If you're not including one of those, then i believe your intuition is correct - DC amps where there's no ripple must equal RMS amps. That's by definition isn't it - RMS gives same heating value as DC ?

I used to work out those problems by simulation in a Basic program using finite difference in maybe 100 steps per line cycle. That'd give me a feel for what was a reasonable approximation.

Am i on the right question here?
RMS current through the transformer winding may not be the same as through its load because Crest Factors come into play. A peaky waveform has higher RMS than a smooth sinusoid.

old jim

davenn
Thanks Jim

nice pdf :)

Dave

I am assuming by "fully controlled" you are using a 4 thyristor (SCR) bridge - with phase angle control? Then you need to include the firing angle in the calculation - and the filtering in the inductor is dependent on the firing angles etc.. If the DC load is purely restive, and the source is ideal ( no inductive or capacitive elements) then the V out is rectified sine ( it will not look like DC as there is no smoothing or filtering) - the math is simple - however to calculate with RL load it is more complicated- I would simulate in LTSPICE.
IMO - no such thing as ripple free DC in this case except when there is 0 load current (;-)

## What is a single phase full wave controlled bridge rectifier?

A single phase full wave controlled bridge rectifier is an electronic circuit that converts alternating current (AC) into direct current (DC) by using four diodes arranged in a bridge configuration.

## What is an RL load?

An RL load refers to a circuit that contains both a resistor (R) and an inductor (L). This type of load is commonly used in AC circuits to control the flow of current.

## What is the RMS value of voltage and current in a single phase full wave controlled bridge rectifier RL load?

The RMS (Root Mean Square) value of voltage and current in a single phase full wave controlled bridge rectifier RL load is the effective value of the AC voltage and current. It is calculated by taking the square root of the average of the squared values of the voltage and current over one complete cycle.

## How does a single phase full wave controlled bridge rectifier RL load work?

A single phase full wave controlled bridge rectifier RL load works by using the four diodes to convert the AC input voltage into a pulsating DC output voltage. The inductor in the load helps to smooth out the pulsating DC voltage, resulting in a relatively stable DC output.

## What are the advantages of using a single phase full wave controlled bridge rectifier RL load?

The advantages of using a single phase full wave controlled bridge rectifier RL load include a higher efficiency compared to other types of rectifiers, a relatively simple and cost-effective design, and the ability to control the DC output voltage using a variable resistance in the load circuit.

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