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Two Different Transformers (Step Down and Step Up) in Series!

05/06/2018 5:35 AM

Hi,

If we have 2 transformers T1 & T2 connected in series, T1 is step down from 11000V/400V, connected to T2 is step up from 400v/5000V, they are in series, the out of T1 goes to in of T2, the frequency must be 50 HZ.

Is there any possibilities to have variation in frequency during commissioning? so do we need to do synchronization and phase test before commissioning?

Thanks

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#1

Re: 2 Different Transformers (Step Down and Step Up) in Series!

05/06/2018 8:37 AM

Frequency is fixed by input source, phasing must be checked to ensure that all connections are as specified in commissioning documents.

What are your doubts?

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#2
In reply to #1

Re: 2 Different Transformers (Step Down and Step Up) in Series!

05/06/2018 9:31 AM

The only way frequency can ever change is by a non-linear transfer function. The only way a transformer becomes non-linear involves core saturation, a fault condition to be avoided for most power distribution transformers. A non-linear load on the secondary of a transformer will create non-linear currents that are harmonics of the fundamental frequency. Still these harmonic frequencies are not altered by the transformer.

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#7
In reply to #2

Re: 2 Different Transformers (Step Down and Step Up) in Series!

05/07/2018 9:57 AM

Transformer saturation can NOT possibly change the frequency. It will cause distortion and harmonics, . . . but never change the frequency!

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#12
In reply to #7

Re: 2 Different Transformers (Step Down and Step Up) in Series!

05/07/2018 12:59 PM

Harmonic frequencies are integer multiples of the fundamental frequency and as such they are additional other frequencies. It is true that the fundamental frequency is not altered.

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#16
In reply to #7

Re: 2 Different Transformers (Step Down and Step Up) in Series!

05/09/2018 12:49 AM

exactly. good to remind.

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#3

Re: 2 Different Transformers (Step Down and Step Up) in Series!

05/06/2018 12:41 PM

Frequency can’t change unless you’re using a generator.

As for you’re second question, you don’t mention the vector group(s) of the transformers.

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#4

Re: 2 Different Transformers (Step Down and Step Up) in Series!

05/06/2018 5:02 PM

<...do we need to do synchronization and phase test before commissioning?...>

Two things:

1) The approved-for-use issue of the Commissioning Plan document for this particular installation cannot be seen from here, so

2) The forum cannot know who is going to carry this out.

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#5

Re: 2 Different Transformers (Step Down and Step Up) in Series!

05/06/2018 10:06 PM

The question seems a little strange, can you post a drawing. I assume you mean the output of the step down transformer is fed into the input of the step up transformer, not the input and output windings are wired in series.

I am assuming the step up transformer is being used for something specific, rather than a simple step down from 11kV to 5kV.

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#6
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Re: 2 Different Transformers (Step Down and Step Up) in Series!

05/07/2018 8:17 AM

Yes, that's what I mean, the step up transformer out put (5000v) 2 phase is fed to ozone generator. is this could effect the frequency? which may cause tripping issues?

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#8
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Re: 2 Different Transformers (Step Down and Step Up) in Series!

05/07/2018 10:29 AM

Aha, NOW you introduce the term “tripping”!

What is tripping?

Why are you suspecting it has to do with frequency?

I suggest backing up and starting from the beginning. All-in-all, it is HIGHLY more likely to be something MUCH more simple than trying to figure out bizarre ways to make it complicated: the concept popularly known as “Occam’s Razor”.

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#9
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Re: 2 Different Transformers (Step Down and Step Up) in Series!

05/07/2018 10:38 AM

My guess is that you're trying to blame the ozonator manufacturer so that you can justify why your external circuitry keeps tripping.

There's too much guessing without a schematic and much more detail. Either post the necessary information or contact the manufacturer and get your answers from the best informed source. It would also be appreciated if you would give us feedback on the results of your calls. Engineering via anonymous strangers in a forum is a major fail for your client.

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#10

Re: Two Different Transformers (Step Down and Step Up) in Series!

05/07/2018 11:57 AM

my question is why are you using this configuration? Seems an over use of transformers!

Why did you not use a multi-tap Tx for the step down and select your required output voltage?

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#11

Re: Two Different Transformers (Step Down and Step Up) in Series!

05/07/2018 12:12 PM

What is the rating of your Ozone Generator? Perhaps a few watts? Yes it is possible that there is some current variation in your Ozone Generator load, but that won't affect the primary frequency of your voltage.

This sounds like a large T1 transformer verses a small T2 transformer. I can't imagine a need for a KW rating for an Ozone Generator.

Perhaps you are chasing a coincedence rather than the actual problem. Too many old style DC power supplies can generate a lot of harmonics which increases the likelihood of random circuit breaker trips.

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#13

Re: Two Different Transformers (Step Down and Step Up) in Series!

05/07/2018 4:34 PM

Have you been let loose to play with 11KV transformers - and don't know what your doing - because that is what your questions suggest....!

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#14
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Re: Two Different Transformers (Step Down and Step Up) in Series!

05/07/2018 5:02 PM

So... you've never hooked up a Neon sign? that's probably what we are discussing here for something like an ozone generator. A few watts, but very high voltage.

It would be courteous for the OP to check back in with the rest of the details though.

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#15
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Re: Two Different Transformers (Step Down and Step Up) in Series!

05/08/2018 8:01 AM

From that, are you saying it is perfectly safe to play around with 11kv transformers if you don't know what you are doing.

For my part I have worked on old CRT equipment, not that I was taught or knew much about it - except you could get an almight 'poke' if you touched an anode or got too near when a spark could leapt across the gap - but you could draw an arc with an HT neon tester type screwdriver but feel nothing.

...even so, it is useful to know what you are doing.

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#17

Re: Two Different Transformers (Step Down and Step Up) in Series!

05/09/2018 1:03 AM

there is no change in the frequennyy

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#18

Re: Two Different Transformers (Step Down and Step Up) in Series!

05/13/2018 8:43 AM

Hi All,

I am not the one who made this kind of arrangement any way, so hold no blame! we are just trying to live with and solve the problem.

The ozonator got a PSU - Power supply unit with constant voltage (5500v) and variable frequency (10 - 1000)Hz,

so still the question is there, is it must be in this case before commissioning the line to consider the frequency?

In other hand, if there is a frequency protection relay on the upstream will it trip? Up stream is 11000v/400v transformer with 50/60Hz, so there is a big change in the frequency in the system?

Here is broucher of the ozonator PDA type:

http://www.mequipco.com/documents/PDO_PDA_2010_Lo_Res.pdf?lbisphpreq=1

in page 3 about PSU with variable frequency to control the O3 concentration.

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#19
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Re: Two Different Transformers (Step Down and Step Up) in Series!

05/13/2018 8:57 AM

That's like questioning if the variable power PSU in your microwave oven somehow affects the power level in your toaster!! Call the manufacturer and find a qualified engineer to assist you.

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#20
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Re: Two Different Transformers (Step Down and Step Up) in Series!

05/13/2018 9:45 AM

I think you are misreading the information you have. The ozonator PSU will successfully work with a power source frequency of 10 to 1000 Hertz. The PSU does not alter this frequency it just has a broad acceptable range of power frequencies it will accept. Thus if you reside in a place with 50 Hz electric power, you are fine. If you reside in a place with 60 Hz electric power you are fine. If you must use an uncontrolled frequency generator power like a throttled ship engine where the generator will vary from 40 Hz to 400 Hz, you are fine.

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