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Forum Index : Electronics : Inverter Theory Question

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InPhase

Senior Member

Joined: 15/12/2020
Location: United States
Posts: 178
Posted: 11:52pm 23 Dec 2020
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I have only tinkered in inverter electronics. So far I've managed to get a small working HF PSW inverter plugging along with an EGS002, so I'm not very experienced in the practicals.

It occurs to me that an inverter is very similar to a bridged class D power amplifier. I have a 1000 watt amp on the shelf. The question is, could I wire a transformer to the output and feed it a 50/60 Hz audio tone and get usable power? I suppose the transformer should not be less than 2 ohms impedance.

The output stage of a class D is very similar/identical to an inverter. Besides inverters having a built-in oscillator, what are the practical differences?
Edited 2020-12-24 09:53 by InPhase
 
Warpspeed
Guru

Joined: 09/08/2007
Location: Australia
Posts: 4406
Posted: 03:55am 24 Dec 2020
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The answer is yes, in theory.

It will certainly work, but the problem will be that an audio amplifier typically runs at very low average power, with only occasional peaks near up at full max rated power.

Run with continuous 60Hz full power audio tone, it may get rather hot rather quickly, as the heatsinking and output devices may not be suitably rated thermally for continuous flat out operation.

Another problem may be that inverters usually have a soft startup feature and fairly effective current limiting and protection.  An audio amplifier may be rather limited driving some of the really nasty loads a proper inverter often sees.

I suspect it may work, but it may also go bang after a short period.
Cheers,  Tony.
 
oreo
Regular Member

Joined: 11/12/2020
Location: Canada
Posts: 49
Posted: 09:59am 24 Dec 2020
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It will certainly work, but the problem will be that an audio amplifier typically runs at very low average power, with only occasional peaks near up at full max rated power.


Agreed.  Power amplifiers normally deliver about 1/8 of their rated power when used continuously with a speaker. So your 1000w amplifier is good for ~125w continuously. If a manufacturer designed an audio amplifier that could deliver full power continually, it would be way overpriced.  

Pure inductive loads (a transformer) are harder to drive than a speaker, which has a large resistance component. Peak currents will be higher driving a transformer.

To illustrate this, I work for an audio company, and we have a subwoofer with a 4.5kw RMS amplifier, which actually delivers it's rated power.  It's a very conservative design, yet only uses 3 mosfets per leg of the bridge.  

Power amplifiers are more expensive then an inverter, because amplifiers have very low distortion and operate over a wide operating efficiency.
Greg
 
InPhase

Senior Member

Joined: 15/12/2020
Location: United States
Posts: 178
Posted: 12:53pm 24 Dec 2020
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Thanks Tony and Greg! The thought occured to me that amplifiers might be a source of ready-made mosfet boards. Certainly some hand work would need to be done to them. Possibly different fets as well. I will open this amp up to look inside soon, just for fun.
 
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