yeah, i like that... sir tony can you give me the right computation of toroidal 70 volts and 12 volts? in the EI Core transformer here is my computation.
http://www.diyaudio.com/forums/powe...ion-ei-core-transformer-philippines-base.html
http://www.diyaudio.com/forums/powe...ion-ei-core-transformer-philippines-base.html
lovely - very well done - those end bells look fantastic. was wondering today how hard it would be to press them from sheet steel if you had a mandrel made ect and used a 12T press. definately going to have a go at this - i found the winding tool on fleabay also so I will order one from hong kong and give it a try. we can (locally here in AU) get the E I and bobbins / copper wire no problems.
Grega,
50/60 hz Laminated Transformers use Silicon steel instead of ordinary steel to reduce core losses.
Electrical steel - Wikipedia, the free encyclopedia
50/60 hz Laminated Transformers use Silicon steel instead of ordinary steel to reduce core losses.
Electrical steel - Wikipedia, the free encyclopedia
to break the boredom i decided to make a current transformer, ratio is 1:1000 so that an ampere on the primary causes 1mA to flow thr the seconday.....
secondary coil uses 1000turns #33 wire on a 5/8 bobbin:
secondary leads ready for termination...
primary coil is a single turn of an insulated flat copper foil(from an atx psu traffo), pigtails soldered at both ends...
cores are installed next:
brackets installed:
i am going to use this ct to make a 0-10A analog meter using a dc 0-10mA panel meter.
secondary coil uses 1000turns #33 wire on a 5/8 bobbin:
secondary leads ready for termination...
primary coil is a single turn of an insulated flat copper foil(from an atx psu traffo), pigtails soldered at both ends...
cores are installed next:
brackets installed:
i am going to use this ct to make a 0-10A analog meter using a dc 0-10mA panel meter.
finished 2 power traffo's last night:
i used bamboo pegs on 4 holes of the traffo, slightly tight fit, so they don't fall off......
dipping in a pool of varnish, traffo is completely submerged, wait until bubbles disappear, do this several times:
draining off excess varnish, again bamboo barbecue sticks are useful here:
when dripping stops, traffos are hung out to dry, this takes 2 to 3 days:
i used bamboo pegs on 4 holes of the traffo, slightly tight fit, so they don't fall off......
dipping in a pool of varnish, traffo is completely submerged, wait until bubbles disappear, do this several times:
draining off excess varnish, again bamboo barbecue sticks are useful here:
when dripping stops, traffos are hung out to dry, this takes 2 to 3 days:
...which means that polyurethane is better or simply easier to work with?
Regards,
Yugovitz
i got a tube preamp power supply with burnt power supply transformer.
core was 1 1/8 stacked to 1inches, good thing, there was a lable on the leads showing specs,
1. 5volts@3A or 15 watts
2. 600volts ct. @0.050A or 30 watts
4. 15volts@1.5A or 22 watts
5. 10volts@0.3A or 3watts
total demand on the core was 70watts,
looking at RDH4, the core used can only support about 40 watts, so no wonder that the traffo burned out.
this is the burned out traffo:
so i decided to use a much bigger core, 1 1/4 x 1 1/2, this core can support power of 110 watts, so that we have
more than enough headroom....
1. computing for primary turns, Np = 1750/1.875 = 933 turns, @230volts primary,turns per volt = 933/230 or 4.13
2. computing for primary wire size, 110watts/230 = 0.478A, looking at the wire table, #26 wire seems suitable so i
am going to use that.
3. compute for secondary wire sizes;
3.1 300volt winding, i will use just a single winding and convert the rectifier to be assiste by silicon
rectifiers, this will result in lesser transformer heating. so here i choose #30 wire,
3.2 15volt winding, i choose #20 wire.
3.3 10volt winding, i choose #26 wire.
3.4 5volt winding, i choose #18 wire
the new transformer will have bigger windows so that bigger wire sizes can be used.
winding primary coil:
installing the electrostatic sheild:
winding the secondary coils:
completed transformer:
side by side with the burnt traffo:
core was 1 1/8 stacked to 1inches, good thing, there was a lable on the leads showing specs,
1. 5volts@3A or 15 watts
2. 600volts ct. @0.050A or 30 watts
4. 15volts@1.5A or 22 watts
5. 10volts@0.3A or 3watts
total demand on the core was 70watts,
looking at RDH4, the core used can only support about 40 watts, so no wonder that the traffo burned out.
this is the burned out traffo:
so i decided to use a much bigger core, 1 1/4 x 1 1/2, this core can support power of 110 watts, so that we have
more than enough headroom....
1. computing for primary turns, Np = 1750/1.875 = 933 turns, @230volts primary,turns per volt = 933/230 or 4.13
2. computing for primary wire size, 110watts/230 = 0.478A, looking at the wire table, #26 wire seems suitable so i
am going to use that.
3. compute for secondary wire sizes;
3.1 300volt winding, i will use just a single winding and convert the rectifier to be assiste by silicon
rectifiers, this will result in lesser transformer heating. so here i choose #30 wire,
3.2 15volt winding, i choose #20 wire.
3.3 10volt winding, i choose #26 wire.
3.4 5volt winding, i choose #18 wire
the new transformer will have bigger windows so that bigger wire sizes can be used.
winding primary coil:
installing the electrostatic sheild:
winding the secondary coils:
completed transformer:
side by side with the burnt traffo:
Each winding can have it's own VA rating.
The total VA rating for the transformer can be much less than the total of the VA ratings for the secondaries.
It can be a 40VA transformer and still have all those winding ratings.
It is up to the designer/builder to ensure that the transformer is run within it's ratings.