How much distortion is acceptable on residential utility power?

The power company tries to supply a near perfect sine wave. The generators tend to make very good sine waves. The impedance of the local part of the power network and the nearby nonlinear loads are going to be the main source of the distortion.

The fact that the waveform appears clipped suggests that there hasn't been a lot of phase shift applied to the harmonics. The most common sort of nonlinear load is the rectifier feeding a capacitor sort. These tend to clip the peaks. Phase shifts will tend to slide the wiggle down towards the zero crossing.

Dennis Berkowitz wrote in news:C6dvl.288$6%.84 @nwrddc01.gnilink.net:

Operator error?...

I tried two different probes, and both channels on the scope. I also monitored the waveform from a 9VAC wallwart and its the same shape. So its not my scope thats clipping due to high voltage.

And expect to see it get worse as people replace incandescent lamps with compact fluoros.

Sylvia.

I suspect that the population of cf's tends to clip one polarity peak more than the other.

John

"John Larkin" Sillier thanAnyone Else

" That is one of the most crass statements I've seen in all my time on Usenet"

ROTFL....

...... Phil

I expect that the mains power will improve over the next many years. A lot of equipment draws its current in thin spikes at the peaks. Modern designs do this less so.

The CFLs will tend to draw current over a wide part of the cycle. The capacitor after the rectifier is small enough that the the ripple is very large. The transistor circuit makes no effort to regulate anything. The inductor feeding the lamp controls the current. This makes the load appear more resistive than would normally be expected

When LEDs become common, I expect that they will draw well behaved waveforms. It is likely that someone will make a chip for the purpose. Mains goes here, the capacitor here, the inductor here and the LEDs over there. The first guys to get a low cost part on the market, would likely end up owning the whole market

Do you think the half-wave-rectifier diode polarities are exactly randomly distributed?

John

"MooseFET"

The CFLs will tend to draw current over a wide part of the cycle.

** 100% WRONG !

The capacitor after the rectifier is small enough that the the ripple is very large.

** Means the charging time is very short - fool.

The transistor circuit makes no effort to regulate anything. The inductor feeding the lamp controls the current.

** All got nothing to do with the actual charging time of that first electro.

This makes the load appear more resistive than would normally be expected

** Total BOLLOCKS !!

Go measure the current draw waveform of a few CFLs - instead of sitting on you FAT ARSE making up WRONG theories and misinforming people.

Have look at figure 11 for a typical current wave.

Figure 12 shows the same lamp operated from a common triac dimmer at full setting.

..... Phil

No it doesn't. Where did you get that idea. The capacitor will start charging when the mains voltage has passed the voltage that the capacitor has discharged down to and continue until some time after the peak. Try reducing the capacitor to zero and consider what fraction of the cycle the diodes will conduct for.

Actually it does effect it in a very important way. Consider the capacitor equal to zero and the transistors trying to regulate case and you will see why.

You are both wrong and rude.

"Sillier than Anyone Else "

** TOTALLY WRONG !!

..... Phil

What would be the mechanism that causes that? .

A half-wave doubler with the screw base shell going to the neutral?

Cheers! Rich

Full-wave bridge on the 4 or 5 I've opened. Here too:

Cheers, James Arthur

I would rather expect that - using a half wave rectifier presumably doubles the size of the capacitor. Which are more expensive - rectifiers or mains voltage capacitors?

Sylvia.

he

with

The ones I've bashed open all had a bridge rectifier. None went with a half wave or doubler. They all seem to feed the tube through a capacitor from a transformer / inductor thing.

should be pretty damn close in USA where they use split 240V supplies half the lamps will appear on each half. (assuming any attention to polarity was made whilst fitting the ES bases to the lamps)

over here here they use BC base lamps and random distribution is pretty-much guaranteed.