Testing a rectifier

This video is on the techniques for testing a bridge rectifier.

*** UPDATE ***

I emailed a good friend of mine, Luc Small ( Check out his YouTube channel https://www.youtube.com/user/lucsmallau ) and he had the following to say:

"I think you are on the right track in thinking the regulator component is messing up your test.

You see, when I saw your blackboard charging circuit I wondered what was limiting the charge current applied to the battery. In the simplest case a resistor is placed in series with the battery to limit the charge current.

But from what I can see the regulator inside the rectifier unit takes the different approach of shunting excess current away from the battery. If you take a look at the first circuit diagram on this page, you’ll see the bridge rectifier and then to the right the shunt regulator using 3 SCRs - silicon controlled rectifiers - which look like diodes with an extra connection:

https://electronics.stackexchange.com/questions/235195/3-phase-permanent-magnet-alternator-with-regulator-rectifier-scr-output-wavefo

(Note this is for a 3 phase system so the bridge uses 6 diodes and the shunt 3 SCRs).

So my guess is that you have a shunt regulator in your unit. It contains an SCR. When you measure from the green to black terminal and get 0.99v, I think you are measuring the voltage drop across the SCR. Ie you are making it behave like a diode.

According to Wikipedia “The device [SCR] behaves as 2 diodes are connected in series with reverse voltage applied.”. That would explain why you are seeing a voltage drop of about 1v, double that of the 0.5v your other diodes are dropping.

I suspect your smaller device is a pure bridge without a built in regulator."

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