Bridge rectifier overheating

Thread Starter

Gabriell

Joined Jan 16, 2016
47
Can you read a schematic? I've developed this one for you.
View attachment 98879

If you can read it, it will help in further testing.

Thank you for drawing that up for me. I think i understand it. However i still have overheating issues in the primary coil and in the bridge rectifier.
I decided to use 600w dc-dc boost converter i bought on ebay to see if that helps but the problem is the same. In this case i did not use a resistor. Should i??? Im boosting the voltage to 64v 2.5amps. The leds are wired in series this time!
here is a picture of the stup
IMG_2306.JPG
 

Thread Starter

Gabriell

Joined Jan 16, 2016
47
After 5 minutes of use my power supply starts to smoke its so hot and the bridge rectifier is not better either even after mounting it on a heatsink....
 

Thread Starter

Gabriell

Joined Jan 16, 2016
47
With the bridge on the heatsink you show, is the whole heatsink getting so hot you can't touch it?
Its almost at that point where you cant touch the heatsink after a few min. But also the transformer gets really hot. It stated to smoke...
Would that be the issue for the rectifier??
 

BillB3857

Joined Feb 28, 2009
2,570
What is the temperature of the bridge and transformer if you disconnect the LEDs? I'm still betting on a sorted diode in the bridge or the bridge is not connected properly. It should be clearly marked for the AC and Plus and Minus terminals. Double check the connections AND test for a shorted diode.
 

Thread Starter

Gabriell

Joined Jan 16, 2016
47
What is the temperature of the bridge and transformer if you disconnect the LEDs? I'm still betting on a sorted diode in the bridge or the bridge is not connected properly. It should be clearly marked for the AC and Plus and Minus terminals. Double check the connections AND test for a shorted diode.

If i disconnect the leds from the circuit then the transformer warms up slowly but it doesnt get really hot and the bridge rectifier stays cool.
I have tested the rectifier and it looks good. The markings on it is clear. Front AC on the right, DC+ on the left and the back is the opposite.
I dont have another rectifier at the moment so i cant swap it out to test it but i will look for one.
 

BillB3857

Joined Feb 28, 2009
2,570
Are the heat sink pads of the LEDs isolated electrically from the LEDs? Have you tried supplying power to just one LED element with a single series resistor? Do the LEDs light up at all? As someone once said to me, "Something's gotta be causin' it."
 

Thread Starter

Gabriell

Joined Jan 16, 2016
47
Quick update:
I pulled out a rectifier from a microwave and it works. I mounted it on the heatsink and so far no overheating issue in the rectifier BUT!
My transformer heats up even faster i think. Just after 1 minute it heats up to the point where i cant touch it anymore....
Any ideas whats wrong?
Also im not sure whats wrong with my first rectifier as they both measure the same! ( Keep in mind this was a quick test without full load so maybe thats the reason for the rectifier to stay cooler the the other one )
 

Thread Starter

Gabriell

Joined Jan 16, 2016
47
Are the heat sink pads of the LEDs isolated electrically from the LEDs? Have you tried supplying power to just one LED element with a single series resistor? Do the LEDs light up at all? As someone once said to me, "Something's gotta be causin' it."

My leds are sitting on the aluminium heatsink. As far as i know they should be isolated, i checked both terminals and nothing is touching the heatsink. Tried the single led test and its all good but my transformer primary coil heats up badly.
 

BillB3857

Joined Feb 28, 2009
2,570
What happens if you have the secondary of the transformer disconnected from any load an apply power to the primary? Does the transformer still get hot?
 

jaclement

Joined Apr 15, 2009
35
The diodes have about a 1 volt forward drop per leg. At 4 amps DC thats about 8 watts. You have it on thermally insulating cloth. It can run pretty hot, but it wants a heat sink. If you builld this into metal chassis, bolting it to that will be plenty.
 
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