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How to arrest the noise signal in the bridge output during contactor on/off

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prakashvenugopal

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Hi all,

I am facing the issue of noise signal comes into my bridge rectifier circuit through transformer 220v.

I am using 220v ac primary --> 22-0-22v secondary. This secondary output is given to bridge rectifier circuit with 2200 uf electrolytic capacitor in the bridge output --> regulator

I am switching ON/OFF the contactor in the same line of transformer 220V ac. Huge noise seen in the bridge rectifier output during contactor ON/OFF. This is reflecting in the regulator output also.

How to solve this noise? Kindly help.

I am attaching the noise signal seen during contactor on/ off in the transformer seconary waveform 0-22v ac measured in oscilloscope and also bridge output signal. Kindly check and please help.

Regards,
V. Prakash
 

Attachments

  • Screenshot_20210814-192500.jpg
    Screenshot_20210814-192500.jpg
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  • Screenshot_20210814-192538.jpg
    Screenshot_20210814-192538.jpg
    416.2 KB · Views: 163

Solution
KlausST
Hi,

these signals are fast. Thus you need a fast capacitor.
Often huge capacitors a slow capacitors.

--> thus add a 1uF ceramics in parallel.

But all this does not help if youhave bad wiring / bad layout.

Klaus
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The OP reports an actual malfunction - but does not specify exactly what form this takes.

regardless, turning the mains Tx on and off every 2 sec continuously will lead to a real malfunction before long ....
 
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Hi,

25 mhz ferrite bead cable snap ferrite and 300khz cable snap ferrite @ source of the transformer secondary reduces my problem to 50%.
For your information.

Regards,
V. Prakash
 

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At the junction plug where the contactors and input to the transformer wire taken. Attachment made.

Regards,
V. Prakash
 

Attachments

  • IMG_20210820_120034.jpg
    IMG_20210820_120034.jpg
    1.1 MB · Views: 122

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prakashvenugopal said:
Yes. It is an malfunction. Not an measurment artefact.
Click to expand...
Probably both. The spikes are not actually on the power supply output, but they reach the connected circuit.
prakashvenugopal said:
Attachment made.
Click to expand...
Is it asking too much to expect a readable (e.g. upright) picture?

1629451424722.png


prakashvenugopal said:
25 mhz ferrite bead cable snap ferrite and 300khz cable snap ferrite @ source of the transformer secondary reduces my problem to 50%.
Click to expand...
Sounds reasonable. You didn't yet report what's the function of the connected circuit and what kind of malfunction was observed.

You showed that common mode chokes reduce the effect of mains transients to your circuit. The actual problem is the noise succeptibility of your circuit, e.g. due to bad layout, missing built-in supply and signal filtering etc.
 
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i now give you a PCB layout doc so you can reduce noise problems (attached)
 

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  • Basics of SMPS Layout _4.zip
    543.1 KB · Views: 71
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Hi,

a transformer with an earth screen between pri & sec, would be very helpful to you too -- and would likely solve your issues.


"You mean isolation transformer"?

Regards,
V. Prakash
 

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No, very few these days, it appears you have not looked up earth screen for transformers - google is your friend

can you explain how an earth screen blocks CM interference ?
 
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Hi,

can you explain how an earth screen blocks CM interference ?

Yes. That is the question i am thinking to ask. How common mode noise will be solved in earth screening of the transformer.?

Regards,
V. Prakash
 

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10 sec google search gives....

www.carroll-meynell.com

110V Electrical Supply Systems - Carroll & Meynell

110V Electrical Supply Systems SystemsThere exists within the power distribution world two different types of 110V supply system.Care must be taken to ensure the correct transformer is chosen for the application.Otherwise there is the possibility of creating a short circuit when connecting...
www.carroll-meynell.com www.carroll-meynell.com
--- Updated ---

1629959980407.png
 
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Hi,

Here we follow this type of transformer only. I had tried with 1:1 isolation transformer also.
230V ac to 230V ac isolation transformer --> my panel transformer input.

Regards,
V. Prakash
 

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Hi,

It seems you don't understand capacitive effects within a transformer.

With a usual transformer there are pri and sec next to each other, thus there is capacitive coupling between pri and sec.

With a trasformer including an Earth shield winding, pri and sec are not next to each other anymore. Thus no capacitive coupling.

Klaus
 
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