Electronics > Beginners

EI375 steel laminate primary transformer calculation

<< < (3/6) > >>

Jwillis:
Sorry I was trying to calculate math at 3 in the morning .Not a good practice at all.Please recalculate

Anyway the primary thickness is defined as the stacking of the windings. If you know the diameter of the wire and the number of stacks you can work out the thickness of the winding stack.

You can calculate the Self Inductance of a Coil as

L=μο(N squared*core area/l)

        L is inductance in Henries
        μο is the Permeability of Free Space (4*Pi*10-7)
        N is the Number of turns
        A is the Inner Core Area
        l is the length of the Coil in metres

The maximum amperage draw a transformer can safely handle is determined by the loads connected to its secondary winding.Since you have to windings on your secondary you need to add the amperage of the 2 secondaries. So you get 3.271Va at the secondary.
Power primary is equal to power secondary  Vp*Ip= Vs*Is  . The current drawn at the secondary is proportional to the current drawn at the primary  you get Va/Vp =3.271/120=0.027Amps =3.24Va
Your core EI357 should be able to handle up to 3.5 to 4 Va if it indeed 35 mm across the outside.


gkmaia:
Thanks for that!

I just want to narrow down to the logic on primary power requirements so I can get the best wire gauge.

The main values I believe we are looking for are:

- Primary turns: to align the core specifications to input voltage and avoid the thing to saturate and blow
- PA: to define what wire gauge will support the current draw on the primary so we don't get the wire cooked

Those are the 2 key things.

If you look at the spreadsheet attached I replicated all your calculations on excel and apparently the PA (as per datasheet) matches the PA (based on secondary) perfectly. Just want to make sure I did those right.




Jwillis:
Some of your parameters have changed like the primary voltage. This will change all the math.  Also recheck your wire gauge diameter. AWG 38 has a diameter  0.1524mm not  0.1007mm. That was my mistake. It wont make any difference to the total number of windings required , but will change the number of windings per stack  and the total stack thickness.

Also could you post the data sheet of the core you are using.I'm guessing on the dimensions based on the closest example I have.

gkmaia:

--- Quote from: Jwillis on August 04, 2019, 11:56:44 pm ---Some of your parameters have changed like the primary voltage. This will change all the math.  Also recheck your wire gauge diameter. AWG 38 has a diameter  0.1524mm not  0.1007mm. That was my mistake. It wont make any difference to the total number of windings required , but will change the number of windings per stack  and the total stack thickness.

Also could you post the data sheet of the core you are using.I'm guessing on the dimensions based on the closest example I have.

--- End quote ---

Yes!!! I wanted to make a live table I could use with other cores/power/voltages.

So if you look at the table bellow you will see that I am using your calculations to generate the results I need to convert my primary from 120v to 240v using the same core.

That was the whole idea as I have one of those Fluke 8012 multimeters that is 120 and has not voltage switch. I have to rewind the transformer to get it working on 240.

Jwillis:
Oh I see. Since New Zealand is 50Hz ,the core area may not be large enough.50Hz core tend to be larger than 60Hz cores for the same power ratings .Does your data sheet mention 50Hz?

Transformers rated at 60Hz should not be used on a 50Hz supply due to higher losses and core saturation, and the resultant higher temperature rise.Transformers rated for 50Hz, however, can be operated on a 60Hz supply without any effects.

Navigation

[0] Message Index

[#] Next page

[*] Previous page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod