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[SOLVED] Inverter noise increased when a refrigerator was plugged in it. Solution please

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israel7732

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My inverter got noisy whenever i plug a fridge in it. Any clue to reducing the noise? Thank you.
 

your inverter capacity is probably not enough to handle load of the frig. The transformer in the inverter is going into saturation and probably causing magnetostrictive noise. Nothing much you can do except get a higher VA rated inverter.
 

israel7732 said:
My inverter got noisy whenever i plug a fridge in it. Any clue to reducing the noise? Thank you.
Click to expand...
As i guess the inverter was noisy well before you plugged in the Fridge. The noise then increased when you plugged it. Naturally the compressor inside the fridge is an inductive load and the inverter is a quazi sine or an square wave one thus the niose generated. The ultimate solution to eliminate the noise is to use a Sinewave inverter.
Cheers
 

The inverter is a sine wave inverter. It was almost not audible before the fridge was plugged in. It became noisy only when it runs the fridge.
 

israel7732 said:
The inverter is a sine wave inverter. It was almost not audible before the fridge was plugged in. It became noisy only when it runs the fridge.
Click to expand...

(sigh)
Which inverter are you using ? What capacity ?
And which frig is it ? What is the compressor size?

Did you read my post above .... or are you one of those who just likes to keep repeating their questions ad nauseum ?

cheers!
 

I built the inverter myself. What i noticed is that the output voltage rose to 240volts from initial 226volts. I guess it could be flux problem as mentioned above. What i intend doing is to adjust the feedback to have 220volts, then I'll tell you if it solves the problem.

- - - Updated - - -

I built the inverter myself. What i noticed is that the output voltage rose to 240volts from initial 226volts. I guess it could be flux problem as mentioned above. What i intend doing is to adjust the feedback to have 220volts, then I'll tell you if it solves the problem.

The fridge is 175watt.
 

Squarewave is not good for inductive load, such as motors.

Can be bad transformer, bad core or bad winding tech, also we dont know nothing about inverter design, better post circuit and some photo to introduce your inverter, maybe some cat near inverter whine or maybe is some coil or cap, who knows, best is to give some details about inverter.

;-)
 
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86_1346793999.jpg
 
Hmmm.... I only see a partial schematic. And from what IS there, it's not clear how you claim that it's a "sine-wave" inverter. Your FETs are setup as a full-bridge config driving a coil - which I suppose is your transformer primary ? Looks pretty square-wave drive to me, unless you have some fancy linear controls on your FETs which are not visible.

Secondly - and I repeat here (and also agree'ing with tpetar & pranam77's comments) - the ONLY device in your setup capable of creating audible vibrations is your TRANSFORMER. Period.

No more comments on this thread.
 

I wish to show the complete circuit diagram but the project is not complete yet. The long socket on the board holds pic16f876a which is generating the sine wave pwm.
I wish to complete the design and finish up my project.
 

I would think that you'd have used a PWM base frequency that
is well above audible. If the noise is at the upper end of the
audible range then maybe the powertrain is seeing some kind
of subharmonic oscillation. If it's at the low end then it might
be magnetostriction of the core. "Noise" is uselessly vague.

Why you'd ask us, blind, what the problem is rather than put
some probes to it and look at the goings-on, I don't know.
You should be able to judge the "noise" frequency and look
for deviations in the gate drive, switch-node, output voltage
or timings that correspond. We can't do any of that for you.
 

Thank you. The noise was largely attenuated when the output was adjusted to 220volts. Yes the transformer is running a high flux desity. I used 12000 gauss. I would reduce to about 8000.
 

Finally. Its was the buzzer that was making the noise. I removed the noise by using a 0.1uf capacitor at the input of the transistor that controls it.
The inverter now works normally. Thanks people.
 

israel7732 said:
Finally. Its was the buzzer that was making the noise. I removed the noise by using a 0.1uf capacitor at the input of the transistor that controls it.
The inverter now works normally. Thanks people.
Click to expand...

My friend, what buzzer ?

I'm glad to see that You make solution for problem.
 

israel7732 said:
......I built the inverter myself.....
Click to expand...

clearly you didn't design it yourself. Pity no one in the forum realised that.

However your "solution" sounds a bit strange. Why would a battery indicator go active ONLY when you plug in a higher load ? You need to investigate this. It might be due to non-optimum wiring/ earth loops/ bad connectors which are causing IR drops on higher loads. This then might be getting interpreted (incorrectly) as a 'low battery'.

I think you should look into it.
 

i designed and built the inverter. i have pluged heavier loads than the fridge. the fridge is 157watt. i used a 600watt drill earlier and there was no problem. the buzzer was making an irregular noise not the normal buzzing sound. if the design was sensing low battery or overload, it is programmed to buzz for at least 1 second.
 

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