Power Supply Dry Cell Problem--- Help me/

[zero1362]

i need power supply for dry cell, the conect power supply diode bridge it´s so really hot...... and hot and blow..... what this is the problem.....

info:

vcc = 44 v
diode bridge = 35 amp
VCA = 120 v / 60 hz
Icell = 17-20 amp

http://fotos.subefotos.com/d063c2dd4928fbaa1aeacfce2cbad82co.jpg

[Philldpapill]

Try putting 3 diode bridges in parallel. Those rated values for the diodes are absolute maximum, with a very good heat sink on them. If you have just one diode bridge sitting in the open air with no heat sink, you bet they'll blow.

Normally, it isn't recommended putting diodes in parallel as they may have slightly lower/higher voltage drops than the other one in parallel. This voltage asymmetry causes one diode to pass up to 99% of the current, while the other diode doesn't take any. The result is an equivalent circuit with only 1 diode bridge in it, with the other one not really used...

However, if you put 3 or more in parallel, it's more likely that the current will be split amongst them. Another alternative, is to put a 0.01 ohm resistor(1' of 14AWG wire would be fine) in series with each diode bridge output, and put the diode bridge/resistor pair in parallel with another pair. This ensures that each bridge will take a fairly equal amount of current due to the voltage drop of the resistors.

However, this whole circuit really isn't the BEST way to go, but I know we sometimes make do with what we have, so I hope that helps.

[zero1362]

Try putting 3 diode bridges in parallel. Those rated values for the diodes are absolute maximum, with a very good heat sink on them. If you have just one diode bridge sitting in the open air with no heat sink, you bet they'll blow.

Normally, it isn't recommended putting diodes in parallel as they may have slightly lower/higher voltage drops than the other one in parallel. This voltage asymmetry causes one diode to pass up to 99% of the current, while the other diode doesn't take any. The result is an equivalent circuit with only 1 diode bridge in it, with the other one not really used...

However, if you put 3 or more in parallel, it's more likely that the current will be split amongst them. Another alternative, is to put a 0.01 ohm resistor(1' of 14AWG wire would be fine) in series with each diode bridge output, and put the diode bridge/resistor pair in parallel with another pair. This ensures that each bridge will take a fairly equal amount of current due to the voltage drop of the resistors.

However, this whole circuit really isn't the BEST way to go, but I know we sometimes make do with what we have, so I hope that helps.

any plans of connection?

[Danger]

Is your bridge rated to withstand voltages running through it? If the rating is printed on it, it's probably the maximum it can withstand for a short period of time and not continuous operation. If I remember correctly, rectified DC voltage is not in a 1:1 ratio with AC that was used to produce it.

[Philldpapill]

Danger is right! The voltage that the rectifier bridge is actually seeing is 170VDC(nominally). The "120VAC" is an RMS voltage, and NOT the maximum voltage. If your rectifier is rated for 200VDC, then you SHOULD be good, but not always. 300VDC rating should be fine.

However, the voltage issue doesn't really give any real reason why the bridge is heating up and failing. If it were an over voltage issue, the bridge would fry in less than a second, usually. You really should double up on the rectifiers, and split the current via resistances as described - IF you choose to go this route. Also, heat sinks are in order...

[Danger]

Once you have an appropriate bridge, one other thing I can recommend is putting a CPU heatsink on it to help with heat. It should work well without any mishaps.