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Jimmy Lalani
What are the effects of adding inductance and capacitance as secondary load of transformer? I am using a Ring /Toroid Transformer.
Jimmy Lalani said:I increased the current upto 2A of Inductor.
Hello Hardy Sir,jim hardy said:Well, what is the impedance of a 38 mh inductor at your line frequency?
What current do you expect per Ohm's Law?
Jimmy Lalani said:What can be the reason for this?
Jimmy Lalani said:I used a signal generator and applied 300Hz frequency and amplitude 400mv.
Make both measurements with the same instrument ?Jimmy Lalani said:What can I do about this?
Jimmy Lalani said:However, when I connected the output of signal generator to a small multimeter, without any load, the multimeter showed 330mv instead of 400mv.
Jimmy Lalani said:In the generator the peak to peak voltage was 1.13 and in the oscilloscope it showed 1.24 V.
Well anything is possible.Jimmy Lalani said:If I want to calculate these parameters mathematically, than is it possible?
Do you know how to calculate resistance of a length of wire ?Jimmy Lalani said:R1,R2
Do you know how to estimate leakage reactance?Jimmy Lalani said:X1, X2
Do you know how to calculate inductance of a coil on a core ?Jimmy Lalani said:Rc, Xc
Wire is usually solid.Jimmy Lalani said:For resistance Of a length of a wire R=pL/A. L=(4*pi(OD^2-ID^2))/H; Is this correct?
I think you need to train your search engine and find tutorials appropriate for whatever is your level of familiarity, which i don't know.. Look for tutorials on transformer design. There are plenty in existence and i don't intend to write another.Jimmy Lalani said:I am not ale to calculate the other parameters. If possible can you please explain me with an example?
?Jimmy Lalani said:Can you please look at the parameters and say if they are correct?
That looks okay except for this:Jimmy Lalani said:I have B=1.57T, I have calculated H using H=(NI)/Le
Le is mean magnetic flux length given by
Le= (pi*(Rout+Rin))/2;
Then µ=B/H;
µr=µ/µ0;
Is this correct?
That catalog is for powdered cores intended for high frequency smps application. What kind of transformer do you have ?Jimmy Lalani said:I recently found this formula for leakage inductance.
Jimmy Lalani said:I am trying to find some relation with the values provided by software with actual measurement of the transformer and also by doing calculations mathematically.
He ignored both Rp and Xp in his OC test which is a practical simplification that you can get away with because it doesn't cause much error.When the transformer is operating on no load, the current drawn by the shunt or parallel parameters is very small about 2 to 5 percent of the rated current. Thus, a low current will flow through the circuit during OC test. In order to be readable by the instruments, the measurements of voltage, current and power must be performed in the low voltage side.
And also, low range current coils and low range ammeter must be selected. The power factor of the transformer on no load is too low which is typically below 0.5 . So in order work with this low value, a LPF watt meter is selected. The equivalent circuit obtained by the OC test is shown below.
Sure it's possible if you know the actual turns ratio. The voltage ratio they give you is not the turns ratio it's the voltage you should expect at normal load.Jimmy Lalani said:1) Is it possible to calculate the no load voltage mathematically? According to my observations it is always between 10-20% more than the rated voltage. However I am interested in calculating it mathematically.
Geometrically that looks fine and is probably close enough for experimenting at home..Jimmy Lalani said:2)For core losses I applied the following method:
The length of the medium flux path is: Lav = Pi*(ID+OD)/2 = 0.198 m.
The result of that will be as good as the 1.1 w/kg number. From where did that come ?Jimmy Lalani said:The mass of the core is: M = Lav *(OD-ID)/2 *H* density =
= 19.8 cm * 1.7 cm * 3 cm * 7.55 g/cm3 = 762 g =0.762 kg
So the iron losses are: PFe = 1,1 W/kg * 0.762 kg = 0.84 W
?? i thought you measured no load current as 5 milliamps. See your 'observation ' table.Jimmy Lalani said:3)And no load current= Pfe/230= 3.67mA (without considering the voltage drop across primary impedence)
Is it correct?
That's why you measure open circuit voltage ratio.Jimmy Lalani said:1) I do not know the actual turns ratio.
Why ? You measured it.. Your questions are circular . What information do you have about the transformer that you would use to calculate its open circuit voltage?Jimmy Lalani said:Is it still possible to calculate the No load voltage?
? Open circuit voltage? To what accuracy? For all practical purposes, no the calculation does not differ. Of course core losses and leakage reactance will have more effect at higher frequency.. . but at no load they should still be small.Jimmy Lalani said:Does the calculation differ for a frequency of 400Hz?
Look up Steinmetz formula for iron loss.Jimmy Lalani said:2) W/kg is an assumed value. However, I found that it does not work for all VA rating. I think this W/kg depends on the VA rating and the frequency considered, because when I performed the test for 200VA 50Hz I got core loss of around 2 W and for 600VA, 400Hz it was around 9W.
Take a look at this old old thread. It addresses similar questions.Jimmy Lalani said:So, I searched on internet and I found that either I should find the W/kg for the given rating of transformer or the Core loss density at that frequency and Bm(Maximum Induction). How can I move on from here?