need a high amperage, low voltage rectifier...

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Hi All,

I am assembling a 50+ amp test rig for car amps. I have procurred and assembled a nice pair of 12v 35A transformers, a few 100,000uF caps, and some really, really heavy gauge wire.

Problem is I can't find rectifiers with high enough current capacity. I am confident the transformers are more than capable of the current...So far I have destroyed several 35A rectifiers, despite mounting them on a large heatsink and using a variac to give a nice slow start to the caps charging. The car amps I have been playing with are in the 2x100w range, and as such should have average current draw in the 20-25A range, but whatever the peak is, it's obviously too high for the bridges I've been using.

If anyone knows of a good product, please let me know...

Alternatively, does anyone know how to make diodes share the current? I could use 2 or 3 of the bridges I already have.

Stuart
 
0.01ohm resistors?

I havent had any trouble finding specs for high current diodes, I just haven't had any luck finding anyone selling them at sane prices. The trivially available prices are a little prohibitive, the individual 150A diodes at digikey seem to be $20-$25, so I'd really want to know I was getting the right parts, before dropping $160 on the table, hence my question...

I was hoping someone knew of a bridge product, pure laziness on my part, but discrete diodes will of course work perfectly. I don't mind paying for a product which will survive the torture, I only recently did the math, 2x35x0.6 is a lot of watts, I may actually need to fan cool my rectifiers...

The 0.01ohm, 10w resistors aren't a trivial item to find either, digikey have some in the 1-3w range, and they are $2-$3 a pop, I dread to think what a 10w would cost...Perhaps I should be using some sort of resistance wire?

Stuart
 
Try stud diodes

You could try stud diodes. The ones used in automotive applications are rated around 100amps or so and are probably the cheapest you'll find.

I have found heaps in junked power supplies (at scrap metal dealers). I can usually pick up something with say 6 or more very high current diodes for a total cost of around $10US. You also get the benefit of a lot of other goodies inside.

Second hand I know...but this usually makes no difference.

Cheers
 
which auto application...

Hi,

Sorry if this seems like a dumb question, but which automotive application are you speaking of? I have no problem getting or using second hand auto parts, I just need to know what to look for...heck at the prices we are talking about I can probably use new auto parts...

Stuart
 
Hey Stuart Easson

Sorry,

I'm talking about the diodes commonly used in alternators. They often come embedded in a block of 6 or so. These are really press fit styles so I may have misled you with the term "stud"

In junked power supplies I often find stud diodes and half-bridges manufactured by the likes of IRF, semikron, siemens etc.

Cheers

piccy of what to look for;
 

Attachments

  • rectifiers.jpg
    rectifiers.jpg
    12.3 KB · Views: 47
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.