if the fuse holds, what else is there to worry about
are you not building heavy duty classA using only tough components😀
maybe it also saves on the switch with a film cap on its terminals
are you not building heavy duty classA using only tough components😀
maybe it also saves on the switch with a film cap on its terminals
well. i was thinking of the stress of the transformer.
the capbank will want to draw a Extreme current to charge in a smal amount of time. at the same time that the transformer is restricted by the softstart.
the cap over the switch need to be Y type🙂 (i think) but thats is only to avoid spark in the switch.
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We should not forget that primary current is 4.5(in my case) smaller than one in secondary 🙂.
AudioSan, that exactly what I was talking about:"at the same time that the transformer is restricted by the softstart". The softstart restrict the whole circuit in terms of energy, so you do not have enough energy to melt things down... I hope so 🙂 I have a working transformers as a proof of my words 😛 😀
dazed2, yep, they are WIMA MKP4 4.7uf
with 1000VA ->rectifiers-> 1Kohm resistor->408.000uF caps, i can start it up with or without softstart. if i take away the 1Kohm resistor, the softstart resistors burn up in under half a sec and trip the main fuse🙂
I guess we have some misunderstanding... Demand from caps will be there even if the power cord is unplugged, but it doesn't harm the transformer 🙂
(we should probably discuss it in PM's 🙂
(we should probably discuss it in PM's 🙂
Well it is kinda relavent to me too I'm using.... cough cough... 0.564F in the power supply so I'm a little concerned too.
I decided to get the soft start from Connexxelectronics here but swap out the thermistor for a 5ohm 50W heatsinked encased resistor. I'm hoping it will work....
Its a 1500VA trafo.
PKI : those bypass caps, are you using it to lower ESR and have faster transients?
I decided to get the soft start from Connexxelectronics here but swap out the thermistor for a 5ohm 50W heatsinked encased resistor. I'm hoping it will work....
Its a 1500VA trafo.
PKI : those bypass caps, are you using it to lower ESR and have faster transients?
Do not worry, your transformer will not melt 🙂. I use film caps for ESR, HF oscillations etc and because they are cheap 🙂. Honestly, I never finish any article about how to select a proper value and strict explanation of bypass caps benefits. Just used the forum search 🙂.
Not worried about the trafo melting 🙂 but worried about the 5ohm 50 resistor burning up!
In my F5 I bypassed with 10uF aluminum oil cap which is then bypassed with a polystyrene 0.01uF cap. I found that combination to work really really well.
In my F5 I bypassed with 10uF aluminum oil cap which is then bypassed with a polystyrene 0.01uF cap. I found that combination to work really really well.
I have posted many times that soft start and slow charge are very different strategies.
Soft start is to allow the transformer to start up with blowing the close rated fuse in the primary circuit. This is a short term requirement of about 100 to 300ms.
Slow charge is the current limiting AFTER the transformer has started.
Power Thermistors in the secondary circuit do this slow charge duty very well. This is a much longer term requirement usually longer than 5s.
Both types of current limiter, whetcher using resistor or thermistors increase the supply source impedance. Both types of limiter need to be shorted out to bring back the advantages of low source impedance.
And now the contentious part:
Don't try to achieve the dual duty of soft start and slow charge by inserting a long time duration current limiter in the primary circuit.
I have posted many times that soft start and slow charge are very different strategies.
Soft start is to allow the transformer to start up without blowing the close rated fuse in the primary circuit. This is a short term requirement of about 100 to 300ms.
Slow charge is the current limiting in the smoothing capacitor circuit AFTER the transformer has started.
Power Thermistors in the secondary circuit do this slow charge duty very well. This is a much longer term requirement, usually longer than 5s.
Both types of current limiter, whether using resistor or thermistors, increase the supply source impedance. Both types of limiter need to be shorted out to bring back the advantages of low source impedance.
And now the contentious part:
Don't try to achieve the dual duty of soft start and slow charge by inserting a long time duration current limiter in the primary circuit.
They won't let me edit out the errors in my earlier post so I have rewritten it here.
Soft start is to allow the transformer to start up without blowing the close rated fuse in the primary circuit. This is a short term requirement of about 100 to 300ms.
Slow charge is the current limiting in the smoothing capacitor circuit AFTER the transformer has started.
Power Thermistors in the secondary circuit do this slow charge duty very well. This is a much longer term requirement, usually longer than 5s.
Both types of current limiter, whether using resistor or thermistors, increase the supply source impedance. Both types of limiter need to be shorted out to bring back the advantages of low source impedance.
And now the contentious part:
Don't try to achieve the dual duty of soft start and slow charge by inserting a long time duration current limiter in the primary circuit.
They won't let me edit out the errors in my earlier post so I have rewritten it here.
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I appreciate the explanation. The point you made was lost on me also, so i appreciate your insights. Knowing this now, i am looking for slow charge.
Andrew,
Could you please explain why you shouldn't have soft start AND slow charge in the same module prior to the transformer? If I don't have to, I'm not keen on adding a circuit after the transformer. and before the cap bank.
Could you please explain why you shouldn't have soft start AND slow charge in the same module prior to the transformer? If I don't have to, I'm not keen on adding a circuit after the transformer. and before the cap bank.
Because a primary side Rs does not give an effective current limiter in the secondary circuit.
Because a primary side Rs that is not bypassed quickly generates an enormous amount of heat.
Because a primary side Rs that is not bypassed quickly generates an enormous amount of heat.
softest start solution is "common" soft start circ on primary side, filled with NTC chain , instead of fixed resistors
My english is not very tec.... please someone draw for me. maybe Zen???? 🙂
this is interesting for me since I'm going for 4x47000 for 1 channel. What trafos size VA and Output Volt?
what rail volt is max when cascoded?
will be water cooled, so heat no problem, thinking no insulator between output and sink....
this is interesting for me since I'm going for 4x47000 for 1 channel. What trafos size VA and Output Volt?
what rail volt is max when cascoded?
will be water cooled, so heat no problem, thinking no insulator between output and sink....
