60 Hz waveform distortion

Besoeker

Senior Member
Location
UK
Some newplots.

This morning at midnight, 0000 hours, at home I obtained the following plot with virtually no non-linear loads on in the house.

The blue curve is the full AC line voltage. There appears to be less distortion than in previous plots. i did not capture an expand plot of the peak. At this time of night on a Sunday night I would expect much of Detroit industry has not yet started up.
And not many people out of bed.......:)
 

gar

Senior Member
160112-1314 EST

Besoeker:

Around here during the week when vehicle sales are high many manufacturing plants run close to 24 hours a day. Sundays tend to be non-production. If demand is not too high, then Saturday is also non-production. I will guess that we might have 100,000 or more CNC and robot machines in southeastern Michigan as a load on DTE. These probably all have capacitor input power supplies.

From the curves I saw at the shop yesterday I believe some of the DTE system waveform distortion is a result of the composite load of CNC and similar machines.


mgookin:

Insert image is where this forum has problems.


SG-1:

Can your home scope export the data points from possibly 10 to 20 full cycles with a time resolution of possibly 50 microseconds, about 64,000 time samples?

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Besoeker

Senior Member
Location
UK
160112-1314 EST

Besoeker:

Around here during the week when vehicle sales are high many manufacturing plants run close to 24 hours a day. Sundays tend to be non-production. If demand is not too high, then Saturday is also non-production. I will guess that we might have 100,000 or more CNC and robot machines in southeastern Michigan as a load on DTE. These probably all have capacitor input power supplies.
Not quite sure what you mean by capacitor input supplies.
 

gar

Senior Member
160112-1646 EST

Besoeker:

In the early days of radio there were no electrolytic capacitors. Thus, it was prohibitively expensive to build a DC power supply with diode rectification connected directly to a capacitive filter. Therefore, inductors were used between the rectifier and the capacitor to obtain low ripple. Often times this inductor was the wound magnetic for the speaker.

Thus, the terms capacitor input filter, and inductive input filter were used to differentiate between the two types of power supply filters. See "Radio Amateur's Handbook", 20 th Edition, 1943, p 144. Called Condensor-Input Filter, and Choke-Input Filter here.

As you know a capacitor input filter has a short duration high cuurent input current each half cycle for full wave rectification. Whereas, an inductive input filter with a large enough input inductor has a relatively constant input current by comparison.

I believe what I am seeing in my distorted waveforms is a result of power system source inductance in combination with a large capacitive load that is only connected during a fraction of the cycle. That connection time is determined by the rectifier, series inductance, and capacitance.

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junkhound

Senior Member
Location
Renton, WA
graphics of inductor vs cap, etc.

when a kid, a cheap source of magnet wire was an old radio, the speakers often had a full 5 pounds of magnet wire, typically 34 awg, wound on a 5 in diameter, 5 " long spool.

And don't forget the 'hum-bucker' coil feeding 1 or 2 filaments !

graph below is from an airplane - in the 90's an airline installed a 5" flat screen (Matushita IIRC) in the back of every set, big advertised deal. (flat screen TV cutting edge technology then)

Did not try it out prior to towing plane to the gate and loading for a flight to Tel Aviv. The 4 100 kVA generators would not sync due to harmonics - note the high current distortion. The upper LH diode bridge is the actual circuit - no inductor, straight capacitor input from the diode bridge.

This event triggered a new specification for user harmonics, so boost PFC circuits soon became the standard.

APEC95p.jpg
 

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gar

Senior Member
160112-2430 EST

junkhound:

That is a nice plot of the peak current with a capacitor input filter.

I see you have lived in Renton for a long time. My wife's sister has been there since the 1950s. When her husband was alive he was a pubic school teacher and had his students make a real size canoe from a log as the natives had done in years past. This was a very big untertaking. I believe this was in the papers and you might recall seeing the report.

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