How many turns are there in the primary coil and secondary coil
of the 9 0 9 transformer when I am step downing tranformer from 230 v to 4 v bulb

 

It depends on the size of the transformer core and even then you couldn't say definitely.
A 4V bulb is going to be very unhappy running on 9V!

 

As an approximation *only*, the turns ratio is approximately equal to the voltage ratio. 230 / 18 = 12.78, so an initial estimate would be a 12 or 12.5:1 turns ratio. The ratio will be smaller than the theoretical value to account for energy loss in the transformer core and the windings. The absolute numbers, such as 1200 primary and 100 secondary are entirely up to the transformer designer, the inductance values needed, size, cost, etc.

ak

 

MOD NOTE: Thread title changed.

@Smarty.Ayush224 Please use meaningful thread titles.

I doubt very many people saw "sf" and immediately thought of a transformer windings related question.

 

The absolute numbers, such as 1200 primary and 100 secondary are entirely up to the transformer designer, the inductance values needed, size, cost, etc.

The size, of course, related to the power rating.

 

In my experience with rewinding/modifying EI and toroidal, the average is 3t to 5t/volt for EI and around 2t to 2.5t for toroidal.
If you have an existing transformer it is easy to wind a few turns on and check the turns/volt.
Max.

 

hi,
A rule of 'thumb' is 6 turns/volt for a EI transformer with centre limb of 1 square inch, 3turn/volt for 2 square inches.
As Max says its easy to wind a few turns and measure the winding voltage.
ENSURE adequate electrical safety insulation between the primary mains windings and the secondary winding.
E

 

For transformers at 50 Hz there is an empirical formula W = 30 / S, where S is the cross section of the core in centimeters square, W is the number of turns per one volt. Let Vin = 230V S , S=10cm ^ 2 ==> N1 = 230 * 30/10 = 2300 turns.
For quality transformers at 50 Hz, W = 50 / S

 

RE: Bordodyunov
You popularize the dangerous mistake. The factor by the fact is 50 not 30 (easy to make a mistake using a handwritten figures ). Probably that factor may be applicable at 60Hz but I dont know much about so exotic as American networks, I live in EU and here it stays 50. With extra high quality steel sometimes really it is possible to get close to factor 45 or even 43, but 30 is just the bad dream causing an overheating, giant zero-load currents, and heavy impact on sin form factor.
Actually, the Faraday formula (turns to Volt)=4,44/50(Hz)/B(Tesla)/A(cm2) gives that result at approx 0,9 Teslas. Sure there are in the market materials with B(max)=1,6 Teslas, but it is rare indeed, at least in used equipment. Thus, the best case it has 1,2 Teslas or sooner 1,0 Tesla.

 

Yes, a factor of 30 is given for bad transformers. But such transformers are found in cheap Chinese adapters
Russian Steel

 

Aaarghhh, China.... I know those transformers, what in loadless state consumes not 1% what is normal, or 10% what is slightly arrogant, but they have 50% or 70% the I(o) from the I(max). Result, nonloaded state temperature 90 C and full load state 180 C what is one or pair C under the melt.
And those E408, E411, E413 - dont it seems something rather new? I have few tons of bit older Russian steels of all possible sizes, but none of them are capable for 1,6...1,9 Teslas. Probably Russia made a kinda of technology jump after 1990?

 

Well no. These are relatively old electrical steel. Even earlier they had another marking. Not everything in the USSR did badly! I did not meet newer ones, although I did not undertake any effort. In Russia, factories have focused on new materials.

 

Transformer equation should be N/V=1/(4.44fAB)
So you should be able to get an idea of the number of turns on your transformer by measuring the core size. Most EI patterns are "waste free" meaning that if the overall width of the longest side of the E is W then A will be (W/3)^2.
You can also then estimate the bobbin size, and copper wire diameter, and see if things match up if you measure the coil resistance.
I would suggest using B=1 tesla for unknown irons, but may need to be reduced for poor grade.