Bridge Rectifier Problem

[gary350]

I bought 10 bridge rectiviers. 1 terminal is marked AC, and 1 terminal is marked +DC.

The other 2 terminals are not marked? Which ones are both AC????

 

[ericgibbs]

hi,
Look here. PDF
E

 

[KeepItSimpleStupid]

Hint: https://bit.ly/1x1lFti

Hint: Diagonals are AC and diagonals are DC.
Another hint: The diode scale on your ohmmeter.

 

[KeepItSimpleStupid]

Eric: That's too easy. You have to train them.

 

[ericgibbs]

hi kiss,
Well it is Christmas, so I popped it into his stocking.

Who knows, I may have introduced the OP into downloading and reading the datasheet.

E

 

[gary350]

I wanted to double check to make sure I have it hooked up right, I burned up 2 of these. I have learned they are only good for 15 amps even though they are rated 50 amps. My next plan is to connect several of these bridge rectifiers in parallel on a large heat sink.

I hope the aluminum case is not connected to 1 of the leads?

 

[tunedwolf]

The case is insulated. 50A @ Tc 55 degrees max, so plenty of proper heatsinking is required. I would recommend that you also use thermal compound to help achieve a good bond

 

[tvtech]

My next plan is to connect several of these bridge rectifiers in parallel on a large heat sink.

Now that's a new concept..Bridge Rectifiers connected in Parallel
Never seen it done before.

Regards,
tvtech

 

[Diver300]

You definitely need good heat sinking.

Diodes, and therefore bridge rectifiers, do not parallel well. The voltage drop falls as the temperature rises, so the hottest diode takes the largest current, which can lead to thermal runaway.

When using transistors in parallel, separate emitter resistors are fitted for each transistor. You could do something like that with the rectifiers to keep the currents even, but you would loose efficiency. It is quite complicated to work out how big the resistors need to be to prevent thermal runaway.

 

[JimB]

One point which has not been mentioned, when the rectifier is feeding a large capacitor filter, the current flow in the diodes is in the form of large short peaks at the crests of the incoming voltage waveform.
As a result it is good to specify a rectifier with a current rating which is several times the expected RMS current.
It is also good to "supersize" the heatsink.

JimB

 

[MrAl]

I wanted to double check to make sure I have it hooked up right, I burned up 2 of these. I have learned they are only good for 15 amps even though they are rated 50 amps. My next plan is to connect several of these bridge rectifiers in parallel on a large heat sink.

I hope the aluminum case is not connected to 1 of the leads?

Hi,

As others have noted, diodes dont parallel well. If one diode passes more current it gets hotter and then its characteristic voltage drops so it wants to pass even more current. That might blow it out.

Your bridge just needs a heat sink. That will allow it to run longer without a problem. You can also check the case temperature now and then to make sure it is not getting too hot.