Transformer Windings

[david.rogers]

I need to add a winding to an existing PS transformer. I can calculate/experiment on the windings needed to achieve the correct voltage (allowing for regulation) but as I need 15v @ 1.6A or so, I imagine the type of wire to be used is quite important. I assume (being a tad ignorant about these things) that a greater diameter of wire means higher power (?) but could I run into problems with heat?

David

[Ianm2]

its difficult, the formula is simple but has many parameters, , however, you have to know things like the flux, and dimensions of the transformer, which if a toroid isn't really accessible for us amateurs. how on earth you get it in a frame type I have no idea

I would suggest perhaps 5-10 turns, then measuring, I don't think there is an easy way apart from trial and error.

basically, voltage is down to insulation, and current is wire thickness, you will need insulated magnet wire, perhaps 20 guage, perhaps people more in the know can help here.

[Paul Barker]

I would put more turns on before checking, say 50, then devide to find out tpv, overwind secondary by 10% on a small torroid, if the core is fully utilised.

[david.rogers]

I could only get a frame type from VVT on IOW. They seem quite efficient and delivered the type I ordered quite quickly.

Problem is the windings are insulated and coated in plastic, but I guess - though it won't be too elegant - I can try winding a coil OVER the insulation and see if I can get a voltage. If so, I can experiment with no. of turns until I get around 16.5V. Voltage isn't critical, as the PS (for valve heaters) uses a LM317, so I will need to install a pot and adjust to get 12.6VDC.