Hello community, someone has experience in hysteresis or B-H measurements in medium frequency transformers (1kHz to 20kHz), for power electronics converters.
Normally a lot can be done using good current and voltage transducers.
An oscilloscope can be used as a multiplier (still check if the time window is OK)
Chapter "Measurements" in the book "Inductors and transformers for power electronics" check may be also my publications about the subject.
A current probe from 150 Hz to 50MHz bandwidth is possible.It is also possible to do a no-load test using a square wave voltage.
A good material choice for that power and frequency can be an amorphous or a nano-crystalline core. Amorphous has more losses but is cheaper. Nano-crystalline material is obtained from amorphous by annealing. It it is cut (C-core) additional losses occur at that surface by conduction.
Put a small resistor in series with the excitation coil. The voltage drop in it is proportional to H. Integrate the secondary voltage to obtain a voltage proportional to B. Then you can display the overall B-H loop on an oscilloscope. However, at each location in the transformer there exists a different B-H loop. For example, in HIPERSIL the worst direction of flux is 45 degrees to the rolling direction and the B-H curves depend on the direction of the flux. Sixty years ago at Westinghouse we used thousands of search coils and Chattock coils to measure B and H at various locations. In addition we used thousands of thermocouples to get the iron temperature variation to calculate the core loss by load dump. We did this for many different materials and were then able to design various devices and get the desired results rather than use the old design books that would not work on new materials. This was done for almost all devices using a magnetic material in- cluding multimegawatt turbogenerators. We spent hundreds of thousands of dollars testing the largest devices.
Very well, thank you very much for your contributions
Refer my papers to generate inrush current pattern in laboratory.....
Take care with shunt resistors, they might have 10nH inductance if not special designed for. At 10 mohm it is a time constant of 1 µs 20kHz is 50µs, so 2% or a period = 7.2° shift. The way how the wires get to the shunt is also relevant. This changes a lot in the measured power.
Using the secondary winding changes the behaviour when a square wave is applied: A capacitance at the secondary generates a current in the primary that comes after the edge, and is converted hence in an "active power". So, for core loss measurements it can be better to use only a primary and litz wire, The power is then the primary power - R*I^2.
The litz wire results in less eddy current losses, so that the loss model gets simpler.
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