Frequency fluctuation in a transformer secondary

[zoo123]

hello seek your help.
We have wounded a transformer with 230V 50 HZ PRIMARY And 2200 V Secondary and 5milli amperes at Secondary. This transformer is used for ac ioniser application.
The input circuit has a fuse and power LED connected in series and to primary windings.
The earth is connected to transformer core.
The output high voltage 2.2kv and 5ma IS Connected to ioniser bar.thr. a ground .
fOR SOME REASONS, the frequency at the output is fluctuating between 50 hz to 100 hz. transformer mfg. is not accepting it. The wiring is normal. Can some one help what could be the problem leading to this issue of freq. fluctuating. Unable to answer back to our customer not supplier have a clue. pl. hlp. Thanks

 

[waross]

Metering errors.
That's like saying that I am pulling a car on a rigid tow bar.
The tow car is traveling at a steady 50 kph but the towed car is traveling at a speed varying between 50 kph and 100 kph.
There is probably a distorted wave form with harmonics that are fooling the frequency meter.
Check the frequency with the secondary open circuited.
Look at the wave form with a scope.

The output high voltage 2.2kv and 5ma IS Connected to ioniser bar.thr. a ground .

???

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[IRstuff]

Did you measure frequency fluctuations on the input? Because the secondary is low power, it's possible that the your ionizer is distorting the waveform at the transformer. If you can disconnect the ionize from the transformer, you should see only whatever the mains provide.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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[Compositepro]

In an ionizer there will be no current flow until a certain threshold voltage is reached on the secondary sinewave. Then the current will be limited by voltage drop across the high impedance secondary winding of the transformer, and probably by some current limiting resistors in the ionizer bar. Thus the voltage and current waveforms will not be sinusoidal with the ionizer bar attached to the transformer. Very likely, the frequency meter cannot read this waveform correctly. An oscilloscope will clearly show what is happening.

 

[zoo123]

Hello WAROSS, COMPOSITEPRO AND IRStuff your inputs had been valuable to understand what has gone wrong. While had not validated the root cause, it is simple that the we have 12w and 22watt transormer. the 22 watt transformer apologies i did not say about it. is not functioning because , the transformer is not giving the right threshold voltage despite it sparking.
for the 12watts, we have initially potted the transformer. But, the supplier this time, wanted to know if something is visually breaking that was difficult to identify if potted. May be the transformer not potted is causing harmonics and leading to two frequencies. I DID NTO had an iota o thought but for your three posts made me think. i am confident ath is the issue. thanks once again to all of you. i am going to keep this thread open until i validage and share you back the results. Is there any way we can reduce the harmonics efect in the transformer pl.

 

[IRstuff]

Seems like the previous suggestion to use an oscilloscope is particularly germane, since your presumed insulation breakdown would be most appropriate at the maximum voltage difference. That could lead to a intermittent shorting condition that might have the appearance of a higher frequency signal. And if the shorting does not occur at every cycle, any frequency counting over a finite period of time could result in an average frequency from 50 to 100 Hz. That's why an oscilloscope is critical to the troubleshooting, as you potentially will see the intermittent shorts occurring.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529 Entire Forum list

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[waross]

If there is any rectifying action in the secondary, there will be second order harmonics which may fool some frequency meters.
The old iron based frequency meters were pretty immune to harmonics, not so the electronic frequency meters.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[zoo123]

Hello IRSTUFF and Waross my sincere thanks to both of you for the inputs i receive from you. We planned the following interim corrective actions for now temporarily 1. customer not interested to pot but help us out by pouring a wax on the box to avoid jumps and harmonics due to air gap. etc. 2. Also, the excitation voltage is low in transformer that is matching the voltage or ioniser. So, we wish to study on this more and adjust the excitation voltage or the Ioniser bar ( i dont know how it is possible) this is destructive for the bar as well. but no idea how it could be done.
In future, being a smaller level company, we are planning a permanent corrective action firstto give a go no go gage type of gadget for the transformer supplier he is small though to measure the high voltage winding since the props and meters are costlier. experimenting a relay or circuit breaker than a fuse to trip at the reqd. out put voltage to ensure it is not below the required value.
2. potting is the key to avoid harmonics in my opinion since, we did initially but your views helped to understand better. Sincere thanks and kudos friends. correct me if i am wrong in the interim corrective action.

 

[waross]

It may be more appropriate to abandon this project.
The term "air gap" may be misleading. In regards to a magnetic circuit it refers to any non-magnetic interruption of the magnetic circuit or flux path.
In many cases a device utilizing an air gap will have the gap filled with a solid, dimensionally stable material to accurately set and maintain the proper gap.
If you are rectifying the transformer output, a 100 Hz harmonic is normal and expected.
Some frequency meters will detect this harmonic, some will not.
2.2 kV seems a little low for an ionizer but what do I know.
Is the ionizer working or not?
If it's working why are you agonizing over a normal and expected harmonic.
If it is not working your fixation on a harmonic will probably not help solve your problem.


Bill
--------------------
"Why not the best?"
Jimmy Carter