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Simple bridge rectifier question.
Simple bridge rectifier question.
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Old 14th February 2002, 05:13 AM   #21
JoeBob is offline JoeBob  Canada
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Thanks AudioFreak that diagram's really helpfull. I'll go that route, I'll feel alot safer then just using one 35A bridge.

As for why I didn't just go buy a 50A, because the only ones at my local shop was 35A and lower, and the 50A is like 5 times the price of the 35A if they order it. So I find this solution alot better.

Thanks again for all the help guys.
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Old 14th February 2002, 01:10 PM   #22
paulb is offline paulb  Canada
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Sorry, I was out last night and didn't get to answer your question. Blmn's diagram shows what I was suggesting.
Audiofreak's diagram should work fine too, I think.
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Old 14th February 2002, 02:37 PM   #23
Helix is offline Helix  United Kingdom
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i think audiofreaks' hook-up is better then blmn's 'cos you cannot garantee that the two transformers are exactly the same voltage and hence have slightly uneven rails. Even tho' this doesn't matter much is just better design.

BUT make sure the tansformers are the right way round with respect with each other. Check the AC voltage between taps with DMM, if 0 volts then they are in-phase, if the expected voltage then they are 90 degree out out phase. Just a thought
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Old 14th February 2002, 05:39 PM   #24
paulb is offline paulb  Canada
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Quote:
Originally posted by Helix
i think audiofreaks' hook-up is better then blmn's 'cos you cannot garantee that the two transformers are exactly the same voltage
Um, audiofreak's hookup wires two transformer secondaries directly together - the consequences of uneven secondary voltage would be much more severe in this case.
I think JoeBob is using two identical transformers; if not, I wouldn't use audiofreak's arrangement. Even if they are, I highly recommend fusing each transformer separately.
I totally agree with the comments about checking carefully for the right phasing of the transformers.
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Old 14th February 2002, 06:06 PM   #25
Helix is offline Helix  United Kingdom
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Quote:
Um, audiofreak's hookup wires two transformer secondaries directly together - the consequences of uneven secondary voltage would be much more severe in this case.
no, it's more lightly that the secondaries are more closely matched with each other then two diffrent transformers, in which case, if one is slightly lower from the other, the output voltage is the mid point.

HOWEVER how about using 4 bridges that way there is less current in each bridge, if thats the problem
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Old 14th February 2002, 07:06 PM   #26
Jamie F is offline Jamie F
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PaulB

One bridge for 10x 3886 - at full power? No, in normal use. The 10 channels aren't full range. I made the point to JoeBob about this because I think you've got to be going some to stretch the bridge. I accept that 2 is probably a better idea.

Jamie
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Old 14th February 2002, 08:21 PM   #27
blmn is offline blmn  Brazil
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Audiofreakīs suggestion is better because filtering at the output is easier than Paulīs one, but its more complicated and all the cares related in this thread will be necessary.

regards
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Old 14th February 2002, 08:40 PM   #28
Helix is offline Helix  United Kingdom
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actually i ment 180 degree out of phase, above. sorry
i think u know what i mean anyway
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Old 14th February 2002, 08:55 PM   #29
Geoff is offline Geoff  United Kingdom
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Time to put in my two-penn'orth. Both the previous proposals have problems. The first circuit does not fully utilise the transformer secondary and so potential VA capability is being lost. The second circuit requires closely matched secondary windings (< 0.5V difference) to avoid a high current circulating in the two parallel windings causing a heat build up and reduction in usable VA.

May I suggest that, for the cost of two additional 35A bridge rectifiers, the following circuit be used which will avoid these problems. This circuit has the added advantage the diode current will be halved. I am assuming that I have read this thread correctly and that you have dual-secondary, not centre-tapped, transformers

Geoff
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Old 14th February 2002, 08:59 PM   #30
subwo1 is offline subwo1  United States
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Since Paulb's and Audiofreak's diagrams show full wave rectification, the ripple is 120hz, and the filtering effects will be virtually identical.

Geoff's way is a good way, providing full wave rectification also. I would connect one bridge output from the top tranformer to the bottom capacitor, and one from the bottom to the top.
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