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The calculator is intended for carrying out laboratory work
for obtaining some of the parameters and graphs of dependence of magnetic permeability of ferromagnetic materials on the magnetic field. Another important parameter calculated in this calculator, — potentially attainable growth rate of the efficiency of the second kind — Kη2
, the theory of which is fully reflected in these studies
. This ratio is calculated for the parametric change of inductance with back EMF in the coil, which can be done on the basis of this laboratory work. Also, you can determine the current settings of the generator, which will output this coil on the working mode to a real device. An example of an actual measured performance of the ferrite ring is here
The scheme of the stand for laboratory work is shown below. Generator of sinusoidal signals G1 through a resistance R1, energizes the toroidal winding L1 of the transformer T1.
The entire transformer contains two coils that are wound on a ferromagnetic core with its different sides. On the second winding (L2) measured voltage U2. Actually, the laboratory work consists in feeding gradually increasing the amplitude of the signal of the generator G1, and record the readings of the voltages U1 and U2 in the table. The program calculator will automatically convert them to values of induction and magnetic field strength, to plot and find the value of Kη2
. The more obtained values (dots), the more accurate will the result. To delete the same row in a table just by clicking on (—).
But the program starts its calculations, you must first enter data on the frequency of the generator G1 and constructive parameters of the transformer core T1. These data are entered once at the beginning and do not change throughout the laboratory work. And, if the frequency of the generator resistance R1 and winding L1 data-L2 all clear, the "Length of the midline core, and cross-sectional Area of the core", there may be questions. Depending on the core construction, these parameters can be calculated in different ways. For example, for a toroidal core mean line length is: lm
= (D + d)*π/2, and the cross-sectional area, as follows: Sc
= (D - d)*h/2 where: D — external diameter of the ring torroid, d — inner diameter, π is the number PI, h is the height of the ring. In more detail, and other structures of the cores, the calculation of these parameters can be found here
What initial settings should I choose?
The oscillator frequency is selected within the range of operating frequencies of the ferromagnetic core. If there are several studies, then first select the lowest frequency, for example 50Hz. The number of turns of the windings L1 and L2, for greater accuracy, you need to do as much as possible, but not less than 50. The resistance R1 should be selected in area 10..30 Ohm.
How to measure?
To measure the voltage U1-U2 can be like two multimeters and a dual beam oscilloscope. The first method is suitable for small frequencies: usually the multimeters is designed for the frequency range 50..1000 Hz. The second method allows you to ascend to a higher frequency. In this case, the oscilloscope, you should select the measurement mode of voltage — RMS. Learn more about the stand and the measurements in this calculator read here
What is output?
As a result of constructing the table, we get a graph of the dependence μ(H) and one M(I), which may be needed for these
calculations and finding the optimal mode current in a real device. Also, displays some key values of magnetic permeability (μ0
is the initial permeability, μmin
is the minimum for the whole chart is the permeability, μmax
— maximum) and coefficient Kη2
The value of this coefficient can be recalculated for a different range of values, it is enough to click on schedule to be recalculated Kη2 in the selected range. The range will be highlighted in green. It may be useful to adjust the work area is current in a real device. We must remember that the range reduces the number of measurement points, and hence the accuracy of the calculation.
Can the calculator calculate only the initial permeability?
Yes. If the core feature is not needed, simply enter the basic data and to bring at least one dimension in the table. It must be carried out at the smallest input voltage, but such that the accuracy of the measurements U1 and U2, were sufficient.
Will be lost if the table data if you close the browser window?
Data is stored in the local storage of the browser and when opening the window, they regenerate.
How much data is stored in the browser?
The data is stored until you open a new project the link. Such a reference can be obtained if you click on the "Share" button. In this case, the data is overwritten with the new project.
You can also click on the button "Clear table" then local memory is cleared along with the table. It may be convenient to start a new laboratory work.
As it is more reliable to store data?
Click on the "Share" button and copy the link to your computer. By the way, this link can be shared with friends and teachers to show their laboratory work (your project).