Why output of the bridge rectifier shoots to 1400v after placing a series inductor as a filter?

Thread Starter

amalbabu93

Joined Aug 10, 2018
14
Hi,
I am a designing engineer.I am currently working on A grid tie based solar inverter.My system is capable of driving 1650w load.Having an output of 350v dc with 4.72 A rated.i am using push pull transformer for my design.The problem i am facing now is that when i check the output of the bridge rectifier after output i got a clean waveform of pulsed dc of 400v peak.That seemed ok but when i connected an induct or in series to it, i saw the output of bridge rectifier shooting to 1400v peak.I happen to see severe ringing.Why is that so?will an inductor cause such a heavy ringing especially at the output of bridge rectifier? Is it the material or the type of induct or chosen a reason for this kind of heavy ringing?

The out of the bridge rectifier with just bridge rectifier and with l connected is being attached below.
 

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crutschow

Joined Mar 14, 2008
23,506
If you are an engineer than you know the language of electronics is a circuit diagram.
Please post one of the rectifier bridge and inductor, along with the waveform feeding the bridge.
 

Alec_t

Joined Sep 17, 2013
10,444
A schematic of the whole inverter would be useful, since the input current pulses would be affected by e.g. the output load and smoothing capacitors.
 

mvas

Joined Jun 19, 2017
538
Hi,
I am a designing engineer.I am currently working on A grid tie based solar inverter. My system is capable of driving 1650w load.Having an output of 350v dc with 4.72 A rated.i am using push pull transformer for my design.The problem i am facing now is that when i check the output of the bridge rectifier after output i got a clean waveform of pulsed dc of 400v peak.That seemed ok but when i connected an induct or in series to it, i saw the output of bridge rectifier shooting to 1400v peak.I happen to see severe ringing.Why is that so?will an inductor cause such a heavy ringing especially at the output of bridge rectifier? Is it the material or the type of induct or chosen a reason for this kind of heavy ringing?

The out of the bridge rectifier with just bridge rectifier and with l connected is being attached below.
If the current in the inductor, attempts to suddenly stops flowing,
then the Voltage across the inductor will rise dramatically as the magnetic field collapses.
Also, the inductor will resist an instantaneous increase in current.
This is typical behavior for an inductor.

Do you have a URL-Link to the datasheet for this added inductor?
 
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crutschow

Joined Mar 14, 2008
23,506
If the current in the inductor, suddenly stops flowing
The current in an inductor can't "suddenly stop flowing" but it can complain loudly if you try to stop it.
An inductor will increase the voltage to whatever it takes to keep its current flowing until all the inductive energy is dissipated, and in some cases the voltage can go high enough to cause an arcover.

It sounds like there's no path for that current in the TS's circuit, causing the high voltage spike.
 
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dendad

Joined Feb 20, 2016
3,073
I hope you are actually qualified to design such a thing. In most countries, a grid tied solar inverter must pass official approval testing before it can be used. Please do not proceed if you are not as you run a very real risk of killing someone.
 

Thread Starter

amalbabu93

Joined Aug 10, 2018
14
I hope you are actually qualified to design such a thing. In most countries, a grid tied solar inverter must pass official approval testing before it can be used. Please do not proceed if you are not as you run a very real risk of killing someone.
I really thank for your concern,Actaully i have been into designing for past few years and i have a team with me to handle all the situations.
 

Picbuster

Joined Dec 2, 2013
979
Hi,
I am a designing engineer.I am currently working on A grid tie based solar inverter.My system is capable of driving 1650w load.Having an output of 350v dc with 4.72 A rated.i am using push pull transformer for my design.The problem i am facing now is that when i check the output of the bridge rectifier after output i got a clean waveform of pulsed dc of 400v peak.That seemed ok but when i connected an induct or in series to it, i saw the output of bridge rectifier shooting to 1400v peak.I happen to see severe ringing.Why is that so?will an inductor cause such a heavy ringing especially at the output of bridge rectifier? Is it the material or the type of induct or chosen a reason for this kind of heavy ringing?

The out of the bridge rectifier with just bridge rectifier and with l connected is being attached below.
That's how a step-up circuits works. The only part missing to make a step-up is an integrator ( capacitor).
Normal behavior.

Picbuster
 

Alec_t

Joined Sep 17, 2013
10,444
I see no bridge rectifier in either schematic. Are we to assume it feeds node CCR1_OUT_L in the secondary.png schematic?
 

Thread Starter

amalbabu93

Joined Aug 10, 2018
14
That's how a step-up circuits works. The only part missing to make a step-up is an integrator ( capacitor).
Normal behavior.

Picbuster
Hi,
can you be more clear with this statement "That's how a step-up circuits works".Actually you can see that the bridge rectifier rectifier converts ac to dc pulses and lc filter is to smooth-en the dc power supply>How will this work as a step up circuit.Can you please share your opinion regarding the working of induct-or when a dc voltage is applied across it.Suppose if it is an LC filter the expected output is?
 

crutschow

Joined Mar 14, 2008
23,506
If you still are having an voltage overshoot problem upon startup, you can add a diode across the inductor (cathode to plus side).
That will clamp any overshoot to be no more that about 0.7V above the input voltage.
 

BobaMosfet

Joined Jul 1, 2009
834
See i just tested with a series of inductors in the range of 3mH to 56uH.I found the lowest shoot with 56uH.
So, you guessed. Why didn't you calculate the inductor size based on frequency, since you're working in a frequency domain? In all cases, voltage (drops - which is all that you can measure) is only an indicator of the relationship between electron-flow and the impedance preventing it's flow from one point to another. Therefore, what you're really controlling is the flow of current using a field, and the voltage value will reflect this commensurately.
 

AnalogKid

Joined Aug 1, 2013
8,140
I am a designing engineer.I am currently working on A grid tie based solar inverter.
Then you should be familiar with the concepts in a flyback power supply, the behavior of an inductor in a switching circuit, and the fact that a rectifier diode is a switch. With the inductor's parameters you can calculate the total energy being stored in each cycle and approximate the height of the spike or "inductive kick" in your circuit.

ak
 

Thread Starter

amalbabu93

Joined Aug 10, 2018
14
Hi Guys,
I had calculated the value to be 3mH which i found was too high for my design.Its true that i can calculate the power dissipated in inductor but my major doubt is if you look at the waveform, you can find that there are two peaks for each pulse.Usually when a dc voltage is applied across an inductor, it suddenly opposes the change in current due to the Back emf generated and can see a shoot in first instant.Later on the peak gradually reduces.That is an acceptable behavior of induct-or.But if you look at the output of the L filter you can see that there are two peaks.What could be the possible reason behind second peak corresponding to a pulse in the bridge rectifier output? How can i relate it to the working of an inductor?
 

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