An Extreme Ripple Power Supply Build

RE: An Extreme Ripple Power Supply Build

jc2048 — Mon, 08 Apr 2019 09:38:17 GMT

Don't the test meters need their GND connection to be tied to the output neutral? Otherwise the voltmeter measurement is relative to a floating supply.

If you'd incorporated a Pi, it could have been a 'Raspberry Ripple Power Supply'!

RE: An Extreme Ripple Power Supply Build

three-phase — Mon, 08 Apr 2019 07:13:27 GMT

Nothing wrong with a good old 50Hz ripple on the output - perfectly normal as far as I can see. [View:/resized-image/__size/16x16/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-dd58cf48-7a30-4434-8991-8712faf7de72/contentimage_5F00_1.png:16:16]

I would agree with lui_gough to place protection on the secondary side of the transformers as well as the primary. It also aids with fault finding, so if the secondary fuse remains intact, but the primary blows, you know the fault is more likely to be within the transformer or associated wiring.

More complicated to add, would be to include some thermal protection for the transformer or some sort of temperature warning for the winding.

Kind regards.

RE: An Extreme Ripple Power Supply Build

Gough Lui — Mon, 08 Apr 2019 04:48:16 GMT

[mention:f80b53cee57c44bc9d7c577d07d7c791:e9ed411860ed4f2ba0265705b8793d05] - I don't claim to be an expert, but there are a number of notes and suggestions I would make.

1. Consider putting fuses on both primary and secondary sides of the Variac. They are expensive and deserve to be properly protected - consider the possibility you have a 1A rated Variac input of 120V fused at 1A on the primary. If set to step down to an output of 1V, does this mean you can draw 120A at 1V from the Variac? Of course not. Due to the shared winding, the winding is limited to 1A, so whether output is 1V or 120V, the output should be limited to the rating (or slightly above as short term abuse can be tolerated). Of course, the primary fuse wouldn't blow in this example as at 1A/1v, the primary fuse sees 1/120A of load - so best to have a fuse on the secondary or both sides (my preference).

A second reason is in case whatever you plug in is powered and applies significant DC to the winding which could burn the insulation and destroy the Variac. Best to be safe as fuses are cheap.

2. Consider scraping off some insulation from the side and tapping the Variac to provide your low voltage supply for panel meters - could save a transformer but the cost could be a tiny load on your Variac at all times that you might need to think about.

3. Perhaps also consider circuit breakers instead of fuses if you're prone to accidents.

- Gough

RE: An Extreme Ripple Power Supply Build

genebren — Mon, 08 Apr 2019 03:31:17 GMT

John,

This looks like another interesting build. And yes, the title was a little catchy.

I can see the use for a good A/C supply, although in my case, I live in such a D/C world. Only recently (my home automatic project) I was developing a A/C switch load, and was thinking that it would be nice to have a variable A/C supply. Not only did I not have one, I had a hard time finding a A/C line cord that I could sacrifice to plug in my small. mains level, power supply (module) that I was going to use to power the device. (I once had a box full of power cords, but I seemed to have lost them in the move)

Good luck on finding the right path for this project to take.

Gene