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The plastic tape that covers the transformer, is it only there to protect the Windings?
Ive seen hifi transformers laying in a plastic "cup" and it was my intention to make one of these in my 3D printer and put the transformer in it.
Why then? The Cables needed som work so i had to take the plastictape off.
Is there any good reason that i shouldnt?
why did you need to work on the transformer ?
if you only wanted longer wires then I would of spliced extension wiring to the transformer
if you removed some turns from a winding to lower the output voltage
then I would replace the original tape with new heat resistant tape
eg
glass cloth electrical tape with thermosetting poly acrylate adhesive/ heat class F
Any 3D printed support needs to withstand the temperature the transformer runs at
your probably looking at a 3D plastic part that needs to be safe at 130 to 150 C
and not prevent the natural cooling of the transformer
John
The rubbercoat of the wires was falling off so to fix this I had to take the tape off.
I just did a little research and found out that I could just buy one of these cups, they are made of metal.
I thought that if i put the cover on i dont have to rewind the protection tape.
OK , that makes sense renewing the old insulation
I would still replace the tape
Is this Mounting Disc the type of thing your looking out ?
https://uk.rs-online.com/web/p/mounting-kits/6719208/
using a Neoprene Disc
https://uk.rs-online.com/web/p/mounting-kits/6719211/
helps to even out the pressure on the transformer
just watch out you don't accidently form a shorted turn by
connecting the top metal mounting disk to the bottom disk or chassis
John
Reasons toroids are potted in a plastic case include reducing audible hum (potting compound locks the windings solid) and because they may look smarter! - important for HiFi. To do it properly you need a vacuum potting chamber to drive the resin inbetween the turns of wire. If the primary winding is on the outside you'll need some kind of insulation when potting in a metal can to preserve the breakdown specification - better to have the secondary on the outside in such designs.
Yes, i think im gonna go with that and skip the cover...
Sometime i read about how not to mount one of these transformers but i dont remeber now.
Would this be a bad way? The top metal disc would be connected to the cabinetchassis if i do it like this.
Attachment 26392
Thanks for the info, i decide to go with the tape instead! :smile:
Sorry i forgot to Reply with quote... :shame:
yes, the diagram in post 6 is the usual way to mount an open toroidal transformer
if its fitted in a low profile metal enclosure just make sure the lid can not touch the bolt head and form a shorted turn !
John
Feeling stupid now but, make sure what cant touch the bolt?Quote:
Originally Posted by john swift
The chassis would be in contact with the screw by mounting it in it or am i missing something?
Any connection between the bolt head and the chassis will result in a shorted turn
but if its fitted in a low profile metal enclosure
then it may be possible for the top to be deformed and touch the bolt head if pressure is applied !
Attachment 26393
John
How about the lower end? The nut will be in contact there right?Quote:
Originally Posted by john swift
the lower end is OK as the chassis , bolt and top mounting disk don't form a complete turn around the toroidal core
its only when you close the loop by connecting the mounting disk to the chassis by a conductor outside the core
John
Allright, thanks! :thumsup:Quote:
Originally Posted by john swift
When were at it, what type of fuses would you use for a PSU?
For a toroidal transformer feeding a rectifier/smoothing capacitors you'll need a time delay (T) fuse as the switch on current surge can be VERY large.Quote:
Originally Posted by JW1977
However if you have a fairly constant power drain you can reduce the surge by fitting a NTC thermistor in series
Any idea what the transformers VA rating is ?
As a toroidal transformer inrush current is very large
I would not be supprised if you need a fuse 3 or 4 times what the VA rating would indicate
if you have a 600VA transformer
you may have to use a HRC 10A mains fuse (HRC = High Rupture Capacity)
and check what type of circuit breaker is supplying the radial circuit your mains socket connected to
for example
a type B breaker trips at 3 to 5 times the full load current operating time 0.04 To 13 Sec
a type C breaker trips at 5 to 10 times the full load current operating time 0.04 To 5 Sec
John
PS
if the transformer is large enough you may have to consider using an inrush current limiter
some examples here -
https://sound-au.com/articles/inrush.htm
PPS
more details of a Soft-Start Circuit
https://sound-au.com/project39.htm
Allright, i have to keep looking into that...Quote:
Originally Posted by Voicecoil
Yes, its 800VA. Got some Reading to do about this, thanks!Quote:
Originally Posted by john swift