4100uF/450v *BIG* capacitors... any use?

[MarcelvdG]

7.5/6.3 > 120/110

Are you sure that transformer was fully loaded and not half loaded? Assuming 20 % voltage increase under no load, half load would result in about 10 % extra voltage. That and 120/110 times the mains voltage that the transformer was designed for could together maybe explain the excessive heater voltage.

 

[RockyKing]

I ha used the caps same as yours， 2 series for 600V active power filter circuit， it is frequently explode my Hi-volt MOSFET during powering up. very loud explode and tinnitus， then I have to abandon them.

 

[jcalvarez]

I ha used the caps same as yours， 2 series for 600V active power filter circuit， it is frequently explode my Hi-volt MOSFET during powering up. very loud explode and tinnitus， then I have to abandon them.

I seem to recall Wavebourn had a solution for that. Just a 50W resistor limiting the initial inrush current, and a relay that would shorten the resistor after 30 secs or so. Very reliable setup.

 

[JMFahey]

someone hasn't calculated the number of cats that will fit in a cubic metre to three decimal places of accuracy.

Ok smart boy, so in your view, HOW MANY do fit there?
😆 😆 😆

Transformer winders usually design for rated voltage at full current draw, and most 6.3V AC RMS transformers I've used would spit out 9V DC at the filter cap when lightly loaded

Well, yes, that is one way to do it, specially in cheap under designed transformers, and where load is more bor less constant (as in filaments or lighting).

For power amp supplies, which have varying requirements depending on use and music program, one popular way is to design for nominal voltage +5%, period.
That way you get "safe" rail voltage.
Mainly to take care of magnetization losses, and if they drop under full continuous load, well, so be it.

6.3*1.414=8.9... Plenty of drop out room for a 7805.

You forgot/ignored 1.4 to 2V rectifier loss.

 

[zdenoeddie]

3m9/500V for EL34 PP (image is from state of prototype then). Bleed resistor and soft start is necessary.

 

[kodabmx]

As you know, I use ~4000µF of capacitance in some of my builds. No inrush limiting is necessary using HER308 diodes but it does sound like a degauss when you turn it on 🙂

 

[wg_ski]

I think the “inrush” they’re worried about in posts #102 and 103 wasnt the transformer and rectifier - but if a big cap were used on an active ripple filter with a mosfet. Hungry caps will blow them sky high unless the initial current is limited. Ever gotten hit by flying pieces of a TO-247? Not fun.

 

[kodabmx]

Ah! that makes lots of sense.

I made an "inrush" current limiter with an IXTH6N50D2 and a resistor once... It was to limit the inrush of heaters on an SMPS that was too weak to start into the load.
Datasheet even specs it for start-up circuits... I use them as outputs in an SE amp, too.
https://www.littelfuse.com/media?re...s-n-channel-depletion-mode-ixt-6n50-datasheet