Hi everyone.
Ive just built a 12vDC to 240vAC inverter that uses 4 MOSFETS and a toroidal transformer and it is working OK. When I run my desktop PC on the inverter, i get a loud AC hum through the audio output of the PC.
Is there any way that I can eliminate this hum ? I dont get it using household mains.
Any suggestions welcome.
Cheers.
Is it producing sinewave or squarewave? I assume that you are getting
230VAC RMS (50Hz) output from inverter output.If the inverter produces squarewave output, did you use some pulse-width modulation technology to that your duty cycle varies from
50% (at max. battery voltage) to about 70%(at minimum battery voltage), and the squarewave peak voltage varies from 350V (at max. battery voltage) to 250V (at minimum battery voltage)? Peak voltages outside of 250~350V can damage your computer power supply quite badly (smokes & sparks).With squarewave (or Pulse-width-modulated squarewave) inverter output, a substantial L-C (inductor-capacitor) filter might be able to smooth out the waveform enough to reduce audible hum.
In one instance, we supplied a Ferroresonant Transformer based power conditioner when a customer's squarewave inverter output had to be changed to sinewave & regulated to within 120VAC +/-5%. Ferroresonant tranformer converted squarewave 90~140VAC (60Hz) squarewave (nasty waveform) to regulated 114~126VAC, 60Hz sinewave.
Thank You.
Its a modified square wave
Sounds like you have a ground loop problem. Any chance your inverter is not grounded?
I agree I have PC based MP3 players in my cars and I found if I didn't bond everything it would hum. Particularly be sure your PC is bonded to the amp that you are driving your speakers with. In a car that means a fat wire between the PC chassis and the frame of the car.
Yes, connect it to the mains and use the inverter only for incadescent lights.That's the only load they are capable of supplying, without destroying it.
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I don't see the original post so I'll have to respond this response. Perhaps you're hearing the harmonics. Most of the energy will be in the 1st harmonic. ie 120Hz. A low pass filter would reduce the harmonics. Perhaps
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