I have a ton of toroidal cores used as chokes in a stage lighting dimmer rack, operated at 60 Hz mains power. The thought crossed my mind that I may be able to repurpose them as the transformers for my 500 VDC to 48 VDC full bridge ZVS converter I'm in the process of fleshing out. The converter has a switching frequency of 50-100 kHz. I understand that inductance changes with frequency. What I'm less clear on is how that affects the converter? What happens when a 60 Hz inductor is used at 100 kHz? I've been reading a lot about the subject, but my understanding of it all is fuzzy.
Understanding Toroidal Transformers at Different Frequencies
- Thread starter Frobone
- Start date
ronsimpson
- Joined Oct 7, 2019
- 3,250
The ac losses are too high, and the transformer overheats.
It all depends on the choice of material for the toroid. Materials used for 60 Hz. applications are unlikely to be suitable at higher frequencies and vice versa. Don't waste your time trying to adapt them for purposes they were not intended to serve. Work with a manufacturer to select suitable materials for your application.
There are at least two things to worry about, the self-resonant frequency of a 60Hz. core being operated at high frequency and high AC losses. Neither one of those things is something you want to investigate at those power levels.
There are at least two things to worry about, the self-resonant frequency of a 60Hz. core being operated at high frequency and high AC losses. Neither one of those things is something you want to investigate at those power levels.
Those Toroidal-Choke-Cores are designed for Low-Frequency operation, ( 50/60-Hertz ).
High-Frequency-Toroidal-Transformers use many different Core-Materials depending upon the application.
Low-Frequency-Chokes usually have a flat strip of thin Iron wound into a doughnut-shape.
High-Frequency-Transformers are usually made-up-of some sort of Powdered-Material like Ferrite,
which is then mixed with an Epoxy-Resin to form the Toroidal-Core.
They have completely different operating-characteristics.
In other words .............
If your project works at all,
it will have very poor performance using the Cores that You have.
Texas-Instruments has online Software specifying all the required part-numbers to
make their SMPS-Chips work with the highest possible efficiency,
this includes the required Toroidal-Transformers or Inductors in most cases.
You could possibly use a recommended part-number, or get the specifications that You need.
Toroidal-Transformers and Inductors are VERY MUSHY COMPONENTS.
The Math-Formulas for predicting their real-World performance
only provide "suggestions" and "estimates" ............... and then there's what actually happens.
In any case, "your Mileage may vary" ...............
Larger, rather than minimalistic, Core-Sizes
almost always provide an increase in performance and efficiency.
Toroid-Cores may be stacked to double the Core-Volume / Weight.
.
.
.
High-Frequency-Toroidal-Transformers use many different Core-Materials depending upon the application.
Low-Frequency-Chokes usually have a flat strip of thin Iron wound into a doughnut-shape.
High-Frequency-Transformers are usually made-up-of some sort of Powdered-Material like Ferrite,
which is then mixed with an Epoxy-Resin to form the Toroidal-Core.
They have completely different operating-characteristics.
In other words .............
If your project works at all,
it will have very poor performance using the Cores that You have.
Texas-Instruments has online Software specifying all the required part-numbers to
make their SMPS-Chips work with the highest possible efficiency,
this includes the required Toroidal-Transformers or Inductors in most cases.
You could possibly use a recommended part-number, or get the specifications that You need.
Toroidal-Transformers and Inductors are VERY MUSHY COMPONENTS.
The Math-Formulas for predicting their real-World performance
only provide "suggestions" and "estimates" ............... and then there's what actually happens.
In any case, "your Mileage may vary" ...............
Larger, rather than minimalistic, Core-Sizes
almost always provide an increase in performance and efficiency.
Toroid-Cores may be stacked to double the Core-Volume / Weight.
.
.
.
The type of wire can also be very important to lower IR losses at high current levels at higher frequencies.
https://eepower.com/technical-articles/when-to-use-litz-wire/#
https://www.newenglandwire.com/why-preformed-litz-wire-is-best-for-high-current-magnetic-devices/
For this system @10kHz, I used regular stranded wire for testing but the production testing model will be using litz wire to reduce losses in the single loop induction circuits.
https://forum.allaboutcircuits.com/threads/what-did-you-repair-today.194969/post-1910496
MisterBill2
- Joined Jan 23, 2018
- 19,578
What might work for your inverter power supply would be ti use the torroids at 400HZ or so. The efficiency would be much better than at 100KHZ. And the 400Hz sounds cool on your signal, if the DC is fairly well filtered.
You can evaluate the effectiveness by winding a simple step-up transformer a d using an audio amplifier to drive it on the input side. With a 1:10 step up you can use an incandescent light bulb as the load and evaluate both the effectiveness, by comparing the voltage ratios versus frequency, and the efficiency, power in versus power out. You will also need an audio oscillator to drive it.
In the past, regular 60Hz transformers have been used in DC high voltage supplies for ham radio use. So they do work to some degree.
You can evaluate the effectiveness by winding a simple step-up transformer a d using an audio amplifier to drive it on the input side. With a 1:10 step up you can use an incandescent light bulb as the load and evaluate both the effectiveness, by comparing the voltage ratios versus frequency, and the efficiency, power in versus power out. You will also need an audio oscillator to drive it.
In the past, regular 60Hz transformers have been used in DC high voltage supplies for ham radio use. So they do work to some degree.
