Power load, dummy load (pic)

[KSTR]

Anybody see the error in the schem that draynes linked to?

[anatech]

Hi KSTR,
Yes, but it should be a non-issue for this thread.

Hi draynes,
Only your first two 2N3055's are connected correctly. The rest have a base to collector short, they are fancy forward based diodes.

-Chris

[cliffforrest]

Originally posted by anatech
.... they are fancy forward based diodes.

-Chris

For a brief moment

[draynes]

Originally posted by anatech
Hi KSTR,
Yes, but it should be a non-issue for this thread.

Hi draynes,
Only your first two 2N3055's are connected correctly. The rest have a base to collector short, they are fancy forward based diodes.

-Chris

Yeah, just noticed that myself after looking at it closely. I had gathered up the parts for this thing but had never got around to building it. Oh well, the concept is totally valid for DC testing.

At work I've used constant current electronic loads like this for battery testing. One project I got involved in some years back was manufacturing and testing thousands of battery backup supplies used in cell tower installations. The discharge testing phases were all done with transistance loads in order to maintain a constant discharge current.

I forget now which Asian company made the electronic loads we used, but they were essential for the job. Resistive loads would not have worked.

[anatech]

Hi draynes,

Oh well, the concept is totally valid for DC testing.

Yes it is. Consider feeding a pulsed signal in, or rectified music to test regulated supplies. You could also feed in white noise. There is no way the draw needs to be constant, just a known quantity. Faster transistors may work better in that case. You could even simulate a loud transistor radio and 9 V battery.

The discharge testing phases were all done with transistance loads in order to maintain a constant discharge current.

This also eliminates errors due to connection resistance that come into play with resistors.

-Chris

[cliffforrest]

Active loads with programmable IV characteristics are a standard part of ATE (Automatic Test equipment).

[smps ir2151]

Help to find the schema for this load, broke down and there is no scheme please

http://www.pewa.de/DATENBLATT/DBL_BE...TT_DEUTSCH.PDF

[gorgon53]

It all depends on the test duration.
For short time testing glass coated thick and short ceramic body resistors are best.
I used 6 peaces of 300W rated 0.5ohm resistors to limit the inrushcurrent of a 250kW 3%
regulation 400V 3-phase transformer. The inrush current was in the kA range. The ceramic body has heatcapacity many times higher than metals and is only second to water. I also tried Dale 300W metalcased resistors mounted on a 2 squaremeter! heatsink. But I needed 48 of them and still had reliabilitie issues. One 300W ceramic resistor will be all you ever need for testing audioamps. For longtime testing
of big amps powersupplies you may want forced cooling and/or a couple of more resistors.

[smps ir2151]

That replacement speaker for an equivalent load.

[gorgon53]

Please can explain a bit more what exactltly it is to be equivalent to?