your square at 10khz is so pretty, don´t think more, 0.2db of deviation is not deviation.
see by yourself
SAC Thailand
see by yourself
SAC Thailand
Le Thein Thanh,
1. For an output transformer that has a proper resistive load on the secondary . . .
The primary impedance is affected by at least the following factors, & perhaps more factors too:
The primary to secondary turns ratio.
The primary DCR.
The secondary DCR.
The primary inductance (and the resultant inductive reactance verus frequency).
The leakage reactance, coupling between the primary and secondary (the resultant inductive reactance versus frequency).
The distributed capacitance of the primary (and the resultant parallel resonance of the primary inductance and primary distributed capacitance).
The loss versus frequency of the laminations.
All the above factors may cause you to get results that you did not expect; if you do not account for all of them.
2. I have done many measurements of output transformers, and interstage transformers.
I used a $50,000 Vector Network Analyzer, but do not have access to that test equipment now.
Since that time, I do all those measurements manually.
Because of my experience with those measurements, and many different transformers,
I am not surprised at the differences of primary impedance you are seeing at 50 - 100 Hz, versus at 1kHz.
That frequency ratio is 20:1 or 10:1.
All the frequency dependent factors have some effect, versus the primary impedance verus frequency.
3. Just for fun, drive the primary with a signal generator and series resistor that is at least 10 times the primary impedance.
For your case, use at least 50k Ohms (and turn the generator to it maximum output, to be able to easily see the attenuated voltage that results across the primary).
Do not put a load on the secondary.
Now measure the voltage across the primary with a 10 Meg scope probe; tune the generator to find the maximum voltage across the primary. That frequency is the parallel resonance of the primary distributed capacitance and primary inductance.
You have already measured the primary inductance, so now you can calculate the primary distributed capacitance.
Primary resonance, f = 1/2 x pi x (Root (L x C))
You measured f, you know primary inductance L, now calculate C (the primary distributed capacitance).
I will make a guess that with your secondary Unloaded, the primary resonance is somewhere between 500Hz and 2500Hz.
Please let us know your resultant resonant frequency.
1. For an output transformer that has a proper resistive load on the secondary . . .
The primary impedance is affected by at least the following factors, & perhaps more factors too:
The primary to secondary turns ratio.
The primary DCR.
The secondary DCR.
The primary inductance (and the resultant inductive reactance verus frequency).
The leakage reactance, coupling between the primary and secondary (the resultant inductive reactance versus frequency).
The distributed capacitance of the primary (and the resultant parallel resonance of the primary inductance and primary distributed capacitance).
The loss versus frequency of the laminations.
All the above factors may cause you to get results that you did not expect; if you do not account for all of them.
2. I have done many measurements of output transformers, and interstage transformers.
I used a $50,000 Vector Network Analyzer, but do not have access to that test equipment now.
Since that time, I do all those measurements manually.
Because of my experience with those measurements, and many different transformers,
I am not surprised at the differences of primary impedance you are seeing at 50 - 100 Hz, versus at 1kHz.
That frequency ratio is 20:1 or 10:1.
All the frequency dependent factors have some effect, versus the primary impedance verus frequency.
3. Just for fun, drive the primary with a signal generator and series resistor that is at least 10 times the primary impedance.
For your case, use at least 50k Ohms (and turn the generator to it maximum output, to be able to easily see the attenuated voltage that results across the primary).
Do not put a load on the secondary.
Now measure the voltage across the primary with a 10 Meg scope probe; tune the generator to find the maximum voltage across the primary. That frequency is the parallel resonance of the primary distributed capacitance and primary inductance.
You have already measured the primary inductance, so now you can calculate the primary distributed capacitance.
Primary resonance, f = 1/2 x pi x (Root (L x C))
You measured f, you know primary inductance L, now calculate C (the primary distributed capacitance).
I will make a guess that with your secondary Unloaded, the primary resonance is somewhere between 500Hz and 2500Hz.
Please let us know your resultant resonant frequency.
Last edited:
Thank you very much. I found the cause. OPT has no error, circuit also has no error. The error was caused by my wrong measuring device setup. And here is the result that I have reset. Measurements at 1W. with 300B.
An externally hosted image should be here but it was not working when we last tested it.
