SU119249A1 - Method for determining magnetic properties of ferromagnetic cores - Google Patents

Description

The commonly used methods for determining the magnetic properties of ferromagnetic cores with the aid of three windings — magnetizing, demagnetizing and measuring, superimposed on the tested core, are based on magnetizing by direct current followed by pulsing periodic demagnetizing pulses on it and measuring amplitudes of pulses. measuring winding.

According to the invention, the magnetizing and demagnetizing windings are supplied synchronously, but with a shift in time, rectangular electric pulses. Keeping the amplitude and duration of magnetizing pulses unchanged, change the amplitude and duration of demagnetizing pulses and the duration of pulses taken from the measuring winding loaded with resistance with unipolar conductivity, plot the characteristics of the core magnetization reversal. The described method improves measurement accuracy.

FIG. 1 shows a core hysteresis loop; Fig. 2 shows the voltage pulse shape on the measuring winding; in fig. 3 is a block diagram of a measurement setup for implementing the described method.

The essence of the described method is that the result of the impact on the core of a rectangular current pulse / 1 of a predetermined duration and known amplitude is monitored (Fig. 1). The process of magnetic reversal of the core under the action of a pulse occurs as follows. The current il acts in a positive x direction (along the axis of the amp revolutions), and the current iz - in a negative one. Current 12 is itself

No; 119249

standard periodic rectangular-shaped emulsions of constant amplitude / 2 and duration T2 (not shown). Current d) also consists of a series of square-wave pulses synchronous with impulses / 2 (pulses ti and 12 do not overlap in time).

The amplitude / i and the duration TI (not shown in the drawing) of the current pulses can vary. If / 1 0, then under the action of the pulses 4 the core is re-magnetized along the path (-F2) L. The change in flow in the core LF (/ 2) DF1 (DF in the drawing is not shown). If / i and tj are sufficient for a complete reversal of the core, then under the action of each impulse / core it goes into a state characterized by a point + Ф2. In this case, under the action of current i2, the core is reversibly reversible along the path (+ F2) L and the change in flux DF (/) DFyo. A further increase in / g or TI no longer affects the DF value (/ 2). On the contrary, a decrease in / 1 or TI will lead to the fact that under the action of the pulse / i the core does not completely re-magnetize and its state will be characterized by the point F x. In this case, the change in flow under the action of pulses 4 will be: DF (/ 2) DFdg SDF |, o. We can assume that the pulse / i completely remagnetizes the core, if DFD. DFA ADP1, oh where. For example, you can choose a 0.9.

If we measure DFyo and determine, for different values of TI, those amplitudes / 1, which correspond to DF (/ 2) DFO, 9, we obtain the dependence of the magnetization reversal time T Т TI on the magnetization reversal / Thus, the problem reduces to creating the corresponding generator and measuring DFO, 9; TI; / (TI and / j. Are measured by conventional methods using any synchroscope). ,

ImPulse area of voltage 1 on the winding

 proportional to the change in the flow of DF (Fig. 3). You can “convert the impulse area to impulse duration. For this, it is necessary to shunt W with resistance with unipolar conductivity, the value of which with forward current is much less than the equivalent resistance of core losses. The resistance in countercurrent must be many times greater than the loss resistance in order not to delay the process of magnetization reversal under the action of current 1. These two requirements, with an appropriate choice of the number of turns W, are satisfied by point germanium diodes.

Under this condition, the voltage pulse on Ws has an approximately rectangular shape (Fig. 2). Its amplitude at / h const does not depend on, DF. Therefore, the area of the pulse, and hence the change in flux, is proportional to the duration of the pulse:

D F 1,0, 0; D Fo, e To, d

. The characteristic of the core is removed according to the scheme shown in FIG. 3. It uses two pulse generators: 2 - currents i2 and 5 - currents 1, interconnected by a chroniser 4. On the windings you test. The core cores Wi and W feed pulses from the generators 2 and 3, the voltage from the third winding W, shunted by resistance with unipolar conductivity 5, is fed to the synchroscope 6.

Maximum I are set on measurement generator 3, and Tb is measured with a synchroscope 6. The / i gradually decreases. If the maximum value of / i was chosen not too small, then first the decrease of / i does not affect T i, o. With a further decrease in / 1, the voltage pulse duration t / z decreases. After it decreases to the value of Go, 9 0.9 Ti, o, the amplitude / s is measured. In this way, the first point of the characteristic is obtained. A new (smaller) ti is set. On the synchroscope, t / s- is observed. Then (i) smoothly increases until the voltage pulse duration becomes equal to Go. E, after which / is measured. The measurements are repeated at other pulse durations t. From the points found, the curve / (/ i) is plotted, where G „T1 is an invention

The method for determining the magnetic properties of ferromagnetic cores using three bobbins — magnetizing, demagnetizing and measuring — imposed on the test core, characterized in that, in order to improve the measurement accuracy, magnetizing and demagnetizing windings are supplied synchronously, but with a shift in time Coal electric pulses of direct current, the magnetizing pulses being kept constant in amplitude and duration, and changing the amplitude and duration of the demagnetizing pulse and, measuring the duration of the pulses removed from the measuring winding loaded with resistance with unipolar conductivity, plot the curve of the characteristic reversal of the core.

No. 119249

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