Have you tried connecting the secondaries differently?
For example: SEC1 Red Black, SEC2 Yellow Orange
Original Connection Red Bridge AC, Black & Yellow GND, Orange Bridge AC
Alternative Black Bridge AC, Red & Yellow GND, Orange Bridge AC.
Making this change on one of my torroids made a dramatic reducion in self hum.
I believe it is down to the relative winding directions and positions of the two secondary coils. This was picked up after checking the trafo datasheet!
For example: SEC1 Red Black, SEC2 Yellow Orange
Original Connection Red Bridge AC, Black & Yellow GND, Orange Bridge AC
Alternative Black Bridge AC, Red & Yellow GND, Orange Bridge AC.
Making this change on one of my torroids made a dramatic reducion in self hum.
I believe it is down to the relative winding directions and positions of the two secondary coils. This was picked up after checking the trafo datasheet!
The secondaries on my transformer is blue and black wires but, one of blue and one of black wires has some sort of orange insulation sticking out a little bit from lamination on them, and next two dont have.
An externally hosted image should be here but it was not working when we last tested it.
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i changed, but the hum is still there, before was Blue wire (orange) to diode rectifier / Blue wire and Black (orange insulation) wire connected together as gnd, and Black wire to diode rectifier, now its like this: blue(orange) to diode rectifier / blue and black to gnd / black(orange) to diode rectifier
secondaries are at 43v even transformer is 2 x 40v and its because transformer is 230v but in uk is 240v i think thats the reason to humming - overvoltage its 40gbp for 600w transformer so im not expecting pro audio toroidal or something, will try talema's toroidal's once i finish my av400 second board. Also i calculated that transformer is taking 3.2A from wall and was using 5A fuse because didnt had 3.5A or 4A fuses, i got them and 3.5A fuse got blown, but 4A fuse is working...
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according to this website http://www.judgeelectrical.co.uk/domestic-electrical/fuses/fuse-rating.html Fuse rating = (watts/volts) x 1.25 - 600w/240 = 2.5 * 1.25 = 3.125A with 2.5A fuse i cant even start the transformer when its not even powering something, 3.5A wasnt enough 4A is good. Remember i'm not using some sort of soft start.Output protection with relay from dc is delaying start of amp output and disabling that "pop" sound when you start amplifier.when i start mine lights in the house dims for fraction of second, and i know why because im not using soft start and its taking 600w from a wall in a fraction of second.
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If T 3.5A blows quickly or even at turn on, then that transformer is passing way too much magnetising current which means it´s designed too tightly.
Not a comment on quality per se, just a design choice, and even cheap iron can work without problems IF designer acknowledges what he´s actually using and lowers flux density requirements, through means as simple as designing windings with, say, 10% extra turns or whatever´s required.
Now if you are using a regular fuse instead of a T/SB/delayed one , then by all means get a proper type and rating one, as suggested by Andrew T .
Back to the mechanical vibration, I already suggested re-impregnating it.
Unfortunately. you *should* pull the wrapping or at least *carefully* slit it open so varnish gets everywhere ... would you take a shower with your clothes on ?
Not a comment on quality per se, just a design choice, and even cheap iron can work without problems IF designer acknowledges what he´s actually using and lowers flux density requirements, through means as simple as designing windings with, say, 10% extra turns or whatever´s required.
Now if you are using a regular fuse instead of a T/SB/delayed one , then by all means get a proper type and rating one, as suggested by Andrew T .
Back to the mechanical vibration, I already suggested re-impregnating it.
Unfortunately. you *should* pull the wrapping or at least *carefully* slit it open so varnish gets everywhere ... would you take a shower with your clothes on ?
im always using quick blow glass fuse and, ofcourse i can take shower with closes on - its UK - raining pretty much every 3 days or soIf T 3.5A blows quickly or even at turn on, then that transformer is passing way too much magnetising current which means it´s designed too tightly.
Not a comment on quality per se, just a design choice, and even cheap iron can work without problems IF designer acknowledges what he´s actually using and lowers flux density requirements, through means as simple as designing windings with, say, 10% extra turns or whatever´s required.
Now if you are using a regular fuse instead of a T/SB/delayed one , then by all means get a proper type and rating one, as suggested by Andrew T .
Back to the mechanical vibration, I already suggested re-impregnating it.
Unfortunately. you *should* pull the wrapping or at least *carefully* slit it open so varnish gets everywhere ... would you take a shower with your clothes on ?
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Inductive loads draw big currents at first switch on.
Typically we see the mains fuse rated at three times the maximum operational current. That would require a T7.5A (use T8A) to allow the worst case start up current into your transformer.
BUT !!!!
Using a mains fuse that big risks the fuse not rupturing when the amplifier is abused and goes faulty.
Instead use a soft start that limits the start up current to a level that does not blow a close rated fuse.
I have found for similar rated transformers that a start up current limit that is ~ twice the fuse rating does not nuisance blow that fuse over many cold starts.
So let's assume you use a T2.5A fuse which will allow the transformer to supply full power for all valid operational duties.
That fuse should not blow if the start up current is limited to ~5Aac.
For a 240Vac supply the primary circuit requires a total resistance of 240V/5A = 48r
The primary resistance of a big transformer will be pretty low. Try using a soft start resistor of ~47r that is bypassed by a relay after ~ 100ms to 300ms. I would use four off 10r resistors as my soft start limiter. If that did not offer repeated cold start reliability of the mains fuse, I would not change the fuse. I would add a fifth 10r resistor.
And can i use ntc like CL60 in series with primary winding for inrush current limiting?
In rush current
The in rush current for the worst case is 11 times the nominal current.
regards
The in rush current for the worst case is 11 times the nominal current.
regards
For a direct on line start of an inductive load we generally see the recommended fuse rating is three times the nominal maximum operating current.
The fuse manufacturers already know that their fuses can pass peak currents way above fuse rating when the transient is short.
I have NEVER seen any fuse rating recommendation @ 10, or 11, times the nominal maximum operating current.
The fuse manufacturers already know that their fuses can pass peak currents way above fuse rating when the transient is short.
I have NEVER seen any fuse rating recommendation @ 10, or 11, times the nominal maximum operating current.
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