#### Ravindran

hey guys, i have a toroidal transformer from a home theater which started blowing fuse all of a sudden.
i found a sticker on the top of the toroidal here is a image of it
.

it is 67W transformer
which has a input of 220v primary
and 3 secondaries which are:
15.5v-0v-15.5v which as thickness as

24v-0v
3.6.v-0v
the remaining above 2 secondary and primary has same thickness

question1: what is the amp for all the secondary?
i found out it can be calculated by W=VA
which gives
4.3225A
2.791A
18.6A for each which iam not sure that its correct!.
question2: is the thickness of the copper wire associated with the ampere?
question3: can i change the thickness of the copper wire by like .10mm or even like drastically ?
question4: is there any alternative way for solving the problem other than doing the trivial rewinding job ?
question5: if rewinding is the only way how many turns should i do and how do i calculate the number of turns ?

#### Gruesome

Rewinding does not seem an easy job. Regardless of whether you try to find the fault/short and rewind, or replace the transformer, first you need to find why the fuse blew. It's unlikely the transformer suddenly decided on its own to short out or draw too much current. Something on the secondary side is drawing more current than it is supposed to.
The wattages on the secondary side should add up to 67 Watt. Not knowing the loads on each secondary, you do not know the individual wattages.

The wire gauges (thicknesses) need to be such that very little power is actually converted to heat in the wiring itself, and that not too much voltage is lost (dropped) over the wire.
As an example, if the 24 Volt secondary draws 1.5 Ampere, and the length of the winding is 5 m, a wire with 2 Ohm resistance over 100 meter length will burn 1.5 A * 1.5 A * 0.1 Ohm = 0.225 W and drop 1.5 A * 0.1 Ohm = 0.15 V, which seems acceptable, and should lead to negligible heating. A wire with 2 Ohm resistance over 5 meter would burn 4.5 Watt, and drop 3 V, which both seem excessive.

If you have space on the core, you could always go for slightly thicker wire, but you need to keep the number of turns the same as they were before for each of the coils.

The replacement wires need to be insulated; what is typically used is so-called magnet wire with an enamel insulation.

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#### Ravindran

first you need to find why the fuse blew. It's unlikely the transformer suddenly decided on its own to short out or draw too much current. Something on the secondary side is drawing more current than it is supposed to.
i kindly thank you for your responce
i totally agree there is something drawing more current than it is supposed to
If you have space on the core, you could always go for slightly thicker wire, but you need to keep the number of turns the same as they were before for each of the coils.
unfortunately i dont have enough space
The replacement wires need to be insulated; what is typically used is so-called magnet wire with an enamel insulation.
i havent bought any but glad to know.
This post is posted in introduction section which i dont before and it is reposted in the power supply section i have provided more information about the totoidal in this post,if possible and want to know more plz follow this post