Saturday, November 10, 2018

Toroid core transformers - part 1

This calculator will provide the winding data for our transformers. It has the core data built in for many cores but in case your core is unknown it has a function for that too.

The calculator

The first step is to download and install the calculator. You can do the math if you like but I will use the calculator.

Since we don't always know the core type I will go thru the steps to determine the core parameter first.
(this requires an inductance meter or test procedure to determine the inductance.) The calculator also ID's cores by color code.

run the calculator and click tools.

Select the first option.
The program ask for turns, inductance and dimensions.
I made 4 turns and measured 17uh. The core is 0.5" so I look at T50 for the dimensions.
I transfer the data and the program gives me the AL and ui values.
The FT50-77 give me a fair match. The program displays 3 decimal places which could imply it is very accurate but a single turn will give a large step in inductance with this core. As you can see when I ask about 4 turns it gives 17.6uh. When I ask for a 17uh coil it answers 4 turns. There has to be some round off in the process. Wire spacing will cause some deviation in our results. Inter-winding capacitance will cause some variation.
Try inserting a frequency and you will get the reactance. In my case the coil has a reactance of 220 Ohms at 2 Mhz. This can come in handy as we look at the transformers.

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