Jerry Walker - 2020-03-11
In this last video of the series I finally get round to explainng how the self regulation works in a Ferroresonant Transformer.
I thought the output wouldn't be a sine wave due to the core saturation. Since the output is almost a square wave the RMS voltage is almost (in this case) the same as the peak value which is actually an advantage I might think. I guess the ripple will be lower then with a sine wave so can you use a smaller smoothing capacitor? I guess the current going thru the bridge diodes won't be the small spikes like you get with a sine wave. Anyway great video again, very informative and for me the more detail the better.
Good explanation with the nice scope visuals to further clarify what is going on. That is one neat transformer design!
Very nice presentation! 👌
Would be interesting a load test with input power VS output power!
I remember these being used in the mid 1970s in some TV's. We techs were given some explanation as to the operation, but I never quite understood the magnetic flux flow until seeing this series. Thank you!
Thank you much for the great explanation, I learned something new today
Great series. Any idea how to use these technique (easily) to improve the performance when building your own transformer.
Thank you Jerry, that was an excellent series. I thouroughly enjoyed that!
Thanks, I think that many of these older pieces of equipment are interesting.
I partially understood the theory of operation however I thought that when you saturate a core you create DC and turn the coil into a heater why doesn't the secondary overheat or perhaps a better question is where does the excess energy go, does it go "into" the capacitor as reactance?
It works the other way round. In the first video I mentioned that the secondary flux is what controls the primary current which is why a transformer can 'respond' to changes in secondary load. In the FR transformer the primary part of the core does Not go into saturation and so excess energy is not absorbed. When the secondary goes into saturation it limits the energy (current) in the primary. As soon as the secondary part of the core goes into saturation then this is what limits the input current and so no excess energy is drawn and so no overheating occurs. This is why the magnetic shunts are there as it enables the secondary to go into saturation while the primary does not. I hope this helps.
Cheers Jerry, just had to mentally undo years of "learning", got you now...that's an elegant system.
WHAT DOES THE SECONDARY VOLTAGE DO AS THE CAPACITOR GOES BAD OR LOWERS IT'S CAPACITANCE?
So if I completely understand the primary benefit of this particular transformer is its ability not to be affected by voltage spikes and voltage sags. Some of the drawbacks it’s physically noisy so in a quiet environment it may not be suitable. And earlier did I understand that you said it is electrically noisy so the power might be a little bit dirty?, making it not suitable for audio applications. Possibly not suitable for very sensitive electronics?.
They self regulate over a very wide range of voltage and load conditions. They are also very effective at filtering out mains noise but the output is more of a square wave than a sine wave so may require high frequency filtering depending on the application. The equipment they are normally used in has fans etc so the buzz from the transformer is rarely an issue. Their main drawback (apart from cost and complication) is that they are only efficient over a narrow range of power so need to be matched to the application and the application should have a fairly steady power draw.
I would like to try and Rewind the secondary side of a high voltage Transformer out of a microwave oven . This Transformer has those shunts in it. should I remove the shunts if I want to create a standard Transformer putting out approximately 35 volts AC at about 20A? I'm thinking of winding it with 10 gauge wire. Thank you for any advice you could give on this topic.
Without knowing the specification for the transformer I would not like to comment although if what you have is a FR transformer then I would not recommend using it as a 'normal' transformer although as I always say it will not hurt to experiment.
How does a Ferroresonant Transformer differ from a high-voltage transformer in a microwave? Also on your Ferroresonant Transformer what is the voltage of the resonant winding? I'm considering rewinding the secondary side of a high-voltage transformer to create one similar to yours.
They are totally different. Microwaves generally just use step up transformers to generate high voltage. The resonant winding is wound more for its inductance rather than its output voltage as it forms a tuned circuit with the capacitor. It is calculated and wound in the same way that an inductor would be to give a resonant response at 50 (or 60) Hz.
@Jerry Walker That being the case I would still like to try and Rewind the secondary side of this high voltage Transformer. This Transformer has those shunts in it. should I remove the shunts if all I want to do is create a standard Transformer putting out approximately 35 volts AC? thank you for your reply. I hope I'm not being a nuisance.
Awesome thanks.
Please help me for my dialysis machine, its came with 120v60hz input, 24v 15amp output, 30uf capacitor,...... How can i calculated for modify for same input output on 50hz supply....Or haw can i calculat a new transformer for 50hz on same input output...i have knowledge about general transformer winding calculation.. Please help....
what is the green device on the FRT terminals? it was not there in previous episodes
Akhil Chandramohan - 2020-11-27
It is always a great feeling to learn from the subject matter experts!! Simple and effective explanation with live demo. Thank you Jerry for the sessions of FR Transformer. Honestly, I want to go more detail in to the design aspects of it. It would be great if you can share some mathematical modelling of the same :-)