Filtering generator output?

Hi Eric, First a disclaimer, I know "jack" about AC power. I'm comfortable with a volt and an amp. 100's of volts and 100's of amps are scary.

In principle why not... you could make an L/C low pass to filter out the higher harmonics. (I'm not sure what you'd use for an inductor?.. it needs to handle ~40 amps.) But why bother? You'll lose some power in the LC filter, and I don't think any of your appliances care that much. (But I could be worng.. maybe someone will correct me.)

George h.

What you're seeing is not a harmonic, at least not one generated through the normal means.

You're generator most likely has an alternator and those are current generating devices. The voltage regulator circuit is switching at a few multiples of the 60 hz to build a sinus wave that will stay with in spec with the load you are using.

There is a little hysteresis in the field (rotor) so it makes it a little slow turning off the generator output. This explains why you see the sinus looking effects on top of the 60Hz.

I have a Honda generator that is considered a very well built unit and that too generates a pulsed sinus wave however, if I load it down, it'll clean up.

There are some harmonics but not at the level you're seeing it.

Putting the scope on it isn't really enough load to make it stable.

If you were to have a regulator that averaged over a couple of cycles it would make for a smoother output however, this is dangerous because if a heavy loaded appliance becomes detached or turned off during this cycle, the alternator is left at a state where it was cranking up the field and since it is a CURRENT device, the output voltage will ski rocket for a short moment.

In auto's, it's not as much of a problem because the battery that is attached can briefly absorb that. Maybe you have heard of the term LOAD DUMP>.

Jamie

Why does the waveform matter?

it's probably not worth the effort to remove a little noise from the output. As long as you don't have square wave or really poor grade "modified sine wave" output, anything should run just fine with it. In fact, throwing a load on the generator may be the easiest way to "filter" the output.

If you want to convert that 4500 watt generator into a 2000 or less watt generator with a "perfect" output that will probably struggle or fail to run any motor with a starting coil consider a ferroresonant power conditioner. It will give you the finest of sinewave outputs, complete with voltage and frequency regulation.

Maybe it doesn't. If I was just running motors then I wouldn't care. But my fridge has all these fancy electronic parts that control the temp and the manual warns against using a generator that doesn't put clean enough power. Actually, I think the manual warned against "power sources" that didn't put out AC in the proper frequency range and waveform. Something like that. Anyway, the main reason for the generator is running the fridge and chest freezer and I don't want to ruin the fridge. The chest freezer has no electronics, just electrics. But maybe the "power source" the manual was talking about is an inverter putting out stepped shaped approximation of sine waves. I suppose I could try an old computer out first and if it doesn't complain then maybe the fridge electronics won't either. Eric

I would never buy a refrigerator with electronics. It is not called for. Wh at's more, that electronics in there is probabyl cheaper than the old mecha nical thermostat and defrost timer.

They say it's a feature, but I think it is a bunch of junk. Like the old TV s weith mechanical tuners, suppoeedly a feature but after a few years of ex perienc building them, they were cheaper than a mechanical tuner. In fact u sing a chip to control the volume and other things is cheaper than potentio meters.

Audio ? Hell, making a real volume control even became almost a lost art, u ntil the audiophiles bitched about it. Then they made pots again and put a motor on it for remote control. That cost them.

Everything they do is to make more money. Same here.

Next I need to find an old microwave with a mechanical timer. A long time a go I saw a two power level jobv that didn't cycle it on and off, it actuall y had a second tap on the transformer for the lower wattage.

You probably couldn't buy one now using the US offense budget.

Of course I meant digital tuner...