Mains current measurements.

[x-pro]

I've done some current waveform measurements on the mains side of various loads, using Tek P6302 current probe + AM503 amplifier + Agilent DSO3062 scope. I've clamped the probe on the neutral wire loop of a mains distribution unit, plugged different loads into it, downloaded the waveforms and put the results in a small web album here:

http://www.ant-audio.co.uk/Data/Currents/index.html

I thought it would be interesting to show how distorted these currents are, especially from switch-mode supplies and an energy-saving lamp. However even a simple wall-wart 24V regulated supply produces quite a distorted current into the mains.

I hope that the file names are fairly self-explanatory.

Alex

[JohnAtwood]

Nice measurements! The steady increase in ugly current loads from things like compact fluorescents and switching power supplies has really altered the waveshape of the power, as delivered to the home, with significant "flat-topping" of the wave-form. I've seen this both where I live, which is quite rural and remote, and in Sunnyvale, California, in the heart of Silicon Valley.

The fact that RMS, peak, and average power, as defined for sine waves, are no longer the same can cause voltages in equipment to not be as expected. For example, in a tube amplifier, the tube heaters respond to RMS voltage, a choke-input high-voltage supply responds to average voltage, and a cap-input bias supply responds to peak voltage. With a non-sinusoidal line voltage, voltages within the amp will deviate from each other.

- John Atwood

[jackinnj]

Where's the one where my wife turns on her hair-dryer?

[x-pro]

Originally posted by jackinnj
Where's the one where my wife turns on her hair-dryer?

For a hair-dryer detection you may need this device:



Alex

[pjpoes]

Excuse this question, but is this showing what effect these devices have on the AC waveform of the line they are attached to? Out of curiosity, does this extend to other parts of the line? While not hard to measure or see, I often here people claim that these switchmode supplies dirty the line for other equipment, it would be useful to have images of this, which I believe these are. If you measure the current of a more linear source, say a normal incandescent light bulb, on the outlet below (Paralleled) to the one with the noisy source (Flourescent bulb), do you see the same noise?

[x-pro]

Originally posted by pjpoes
Excuse this question, but is this showing what effect these devices have on the AC waveform of the line they are attached to? Out of curiosity, does this extend to other parts of the line? While not hard to measure or see, I often here people claim that these switchmode supplies dirty the line for other equipment, it would be useful to have images of this, which I believe these are. If you measure the current of a more linear source, say a normal incandescent light bulb, on the outlet below (Paralleled) to the one with the noisy source (Flourescent bulb), do you see the same noise?

I've measured the current consumption, not the voltage on the mains. How badly this distorted current affects the mains voltage waveform would depend on the mains source impedance in that particular point. Current measurements show clearly what rubbish a particular unit "injects" into the mains, but the effect on the other equipment connected to the same mains ring would be different for different installations.

Another important point - it is current that produces AC magnetic field and produces high frequency interference if it is distorted. Voltage in the mains would be just a bit distorted but the current could be a horrible mixture of different distorted waveforms like those on my scope traces.

Alex

[luka]

Hi

I have also done that not long ago in school for energy-saving lamp, thinking it will be nice and all. For switch-mode supplies it is known, only C on input does make high current spikes