Rectifier current/voltage question...?

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Posted by andy evans (A) on September 10, 2016 at 02:02:27

I'm trying to puzzle this out so could do with some help. I have a small mains transformer which is specified as "125-0-125 at 50mA".

I'm trying to establish the safe current capability with:
1. Full wave rectification (2 phase) with a EZ80 with CLCLC, first cap can be 10uF to 40uF. Voltage off load here is 180v

2. Hybrid Graetz bridge, EZ80 plus 2 diodes with choke input. Choke is 15H at 30mA.

I could do with around 200v at 30mA - it's for a 01A preamp so maybe 10-15mA needed.

When the transformer is marked "125-0-125 at 50mA", what current will it actually deliver in these cases?

I've been looking at the Hammond tutorial see here: http://www.hammondmfg.com/pdf/5c007.pdf

So is the "50ma" what Hammond refers to as the "Sec I AC"? if so:
1. Cap input full wave, I DC = Sec I AC = 50mA
2. Hybrid bridge choke input, I DC = .94 Sec I AC = 47mA

Voltage out for 1. is .71 of Sec V AC (250v) = 178v, which is exactly what I get off load
Voltage out for 2. is .94 of Sec V AC (250v) = 235v.

So if all the above is correct, 235v at 47mA looks better for an 01A preamp than 178v at 50mA. The Hybrid bridge option looks win-win, more volts and the same current capability.

This looks like something for nothing! Is all this correct?

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Topic - Rectifier current/voltage question...? - andy evans 02:02:27 09/10/16 (17)

RE: Rectifier current/voltage question...? - hennfarm 12:10:21 09/10/16 (1)

DCR of secondary winding - andy evans 12:37:34 09/10/16 (0)

Hammond Data - free lunch with Graetz Choke in? - andy evans 02:55:36 09/10/16 (14)

RE: Hold on a sec - Russ57 10:42:56 09/10/16 (9)

See text... - andy evans 11:00:01 09/10/16 (8)

Yup, not so - Russ57 11:21:04 09/10/16 (7)

Ah - informative.... - andy evans 12:14:49 09/10/16 (6)

RE: Ah - informative.... - hennfarm 12:25:13 09/10/16 (5)

Have the 01A preamp up and running... - andy evans 14:13:17 09/11/16 (4)

RE: Have the 01A preamp up and running... - euro21 11:03:15 09/14/16 (1)

Ah - useful info on HT voltage for Gyrator! - andy evans 02:41:01 09/15/16 (0)

Just curious, would you do a voltage check? - Russ57 18:14:52 09/12/16 (1)

This is how I wired it - andy evans 12:11:28 09/13/16 (0)

More calcs - peak and average volts - andy evans 03:40:13 09/10/16 (3)

Andy..... - drlowmu 18:06:31 09/10/16 (2)

RE: Andy..... - andy evans 00:57:59 09/11/16 (1)

Much to LEARN !!! - drlowmu 10:51:04 09/11/16 (0)

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