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Hi Ole, the transformer is designed for primary 230v according to the nameplate. With what voltage should I then measure the current? The transformers are also different in the saturation, although the transformers are identical, I think I have a video of it. Greetings Sven
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Von: "[email protected] [EVGRAY]" <[email protected]>
Datum:26.01.2018 10:29 (GMT+01:00)
An: [email protected]
Betreff: Re: AW: Re: AW: Re: AW: Re: AW: Re: Aw: Re: AW: [EVGRAY] Re: Kone & Hector, you guys finally did it!
Hi Sven,
That current is too much. There should be almost no current flowing. This is the full magnetizing current at no load condition. This drives the transformer close to saturation. To make the transformer cheaper the no load magnetization is put closer to saturation to squeeze higher power density through the transformer. Perhaps the transformer is for 220 or 230V?!
Try the measurement at some less current to avoid saturation of the core. At 0.5A there will be 0.5V per Ohm of non-inductive voltage. This also influences the calculation. If using the winding as a choke it mustn't go into saturation as this prevents it from working as a choke. I.e. the inductance almost disappears when saturated and thus prevents the choke from storing any more energy.
Regards
Ole
---In [email protected], <s.friedrich@...> wrote :
Hello Ole, you have quite right volts divided by electricity. that's how I calculate it. The ohmic share I leave except because it is identical transformers unfortunately they do not behave the same. I have set several test voltages and can not get a common linearity. I can apply additional windings to the transformers but there are only partial successes. I have now tuned both transformers at 240 volts. It will flow at both transformers then 579- 582 mA. If I increase the voltage by 1 volt, the current increases massively, but just different for each transformer. I do not know how Hector wants to tune the coils because they always behave differently at different voltages. This 0.003 deviation I can only measure the current. An LCR meter that is so accurate I can probably not afford. Greetings Sven
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Datum:26.01.2018 01:33 (GMT+01:00)
An: [email protected]
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Hi Sven,
I'm not sure I understand. The impedance is the voltage divided by the current. The inductive reactance is the imaginary part of the impedance where the current lags 90 degrees behind the voltage. If the current doesn't lag 90 degrees behind the voltage then there's also resistance in series with the coil.
If the series resistance is small compared to the inductive reactance the reactance can be calculated as the voltage divided by the current because the reactance becomes equal to the impedance when the resistance is decreased to zero. The phase angle Φ between the voltage and current will then increase to 90 degrees.
The figure is taken from here: https://www.electronics-tutorials.ws/accircuits/ac-inductance.html
As the inductive reactance is
Where f is the frequency and L the inductance the inductance then becomes:
Assuming low resistance compared to the reactance XL this latter almost becomes equal to the impedance Z. At high current the core of an inductor can saturate which decreases the inductance. Thus make the measurements at low current to avoid saturating the core. Perhaps this is what you're expiring. The phase angle between the voltage and current can be checked with a scope to be sure it is 90 degrees. Else this simple calculation doesn't apply and the resistance or the phase angle has to be known too for the correct calculation of the inductance.
Regards
Ole
---In [email protected], <s.friedrich@...> wrote :
Hello Ole, it is not accurate at 50Hz to measure the reactive current and to calculate the inductance over xl because these devices work anyway with 50 Hz and I work with this frequency in my experiments. The differences are extremely measured from 250 mH inductance to 1.12 H calculated inductance over xl. Greetings Sven
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Datum:25.01.2018 13:09 (GMT+01:00)
An: [email protected]
Betreff: Re: AW: Re: AW: Re: Aw: Re: AW: [EVGRAY] Re: Kone & Hector, you guys finally did it!
Hi Sven,
"My LCR meter shows completely different values as the calculation over XL"
The calculation also has to take into account the resistance and capacitance. Some LCR meters can measure the device under test at different frequencies to change the influence of the parasitic parts of the device. E.g. like watching the influence of the capacitance and resistance of an inductor.
The parasitic parts of a coil can be found with a sine generator and an oscilloscope and some calculations. The inductance can be found as well.
Inductor model:
The image is taken from here: http://www.techlib.com/area_50/Readers/Craig/switching.htm
For explanation go the bottom chapter "Real World Inductors" on that page.
Regards
Ole
---In [email protected], <s.friedrich@...> wrote :
Hi Ole, Warren, I can not build the capacitors myself. Tuning the inductors is a challenge. I can still calculate the reactance when I put the transformer to 50 Hz 230v and measure the mA. Then Xl = U x I. If I bring both transformers to the same XL value I have the same inductance. My LCR meter shows completely different values as the calculation over XL. Greetings Sven
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Von: "Warren Keillor schoonersolsticemoon@... [EVGRAY]"
Datum:25.01.2018 01:29 (GMT+01:00)
An: [email protected]
Betreff: Re: AW: Re: Aw: Re: AW: [EVGRAY] Re: Kone & Hector, you guys finally did it!
Sven
You change the uf value by simply taking scissors and trimming down the aluminium foil that is inside the plastic sheet. You can get very high tollerances as you discover this sloppy primitive method of making capacitors.
Other than being larger than commercial capacitors, they are very good at keeping the correct values through a very large voltage range.
Hot glue is good to stick the rolls tight against moisture. I use 3M clear tape for holding the roll rolled up tight, and temporarly placing parts. Super glue the electrodes in place.
Cheers
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