SU563653A1 - Apparatus for measuring ferromagnetic material coercivity force - Google Patents

Description

one

The invention relates to the enrichment of ferrous ores and can be used in the beneficiation plants to control the magnetic characteristics of the ore during its transportation with a conveyor belt or an aqueous medium.

Random devices for measuring the coercive force of materials based on measuring the distortion of the sinusoidal shape of the magnetic flux curve, containing a magnetization unit with a constant magnetic field, a demagnetizing unit with an indispensable magnetic field. Due to the fact that the magnetization reversal curve (hysteresis loop) is not a straight line, distortion of the sinusoidal shape of the demagnetization wave curve of its current occurs. The coercive force is determined by the degree of these distortions and, in particular, by the amplitude of the third harmonic. However, the accuracy of measurements of such devices developed for discrete control of parts and transferred to the conditions of measurement of the properties of the flow of material is insufficient.

Devices for measuring the coercive force of ferromagnetic materials are known, which contain primary and secondary windings wound on a toroidal sample, a ballast resistor connected in series with the primary winding, two pulse shaping circuits that give out pulses at the moment of passing through zero voltage on the secondary winding and voltage on the ballast resistor, a circuit for measuring the pulse retardation of the secondary winding relative to the pulses of the ballast resistor. The coercive force is determined by the runway: the duck time to the meleda by the transitions through the zero value of the electromotive force induced in the secondary winding by the magnetic flux and the voltage on the ballast resistor proportional to the strength of the magnetic field. However, such devices also have insufficient measurement accuracy.

The purpose of the invention is to improve the measurement accuracy.

This is achieved in that a device for measuring the coercive force of ferromagnetic materials, containing a magnetizing winding connected to the input of the phase-shifting unit, a sensitive element, an amplifier and a recording device, additionally introduces two ferrodynamic compensating units, the excitation windings of one of which are connected to the input of the phase-shifting unit and the excitation winding of the second - with its output, the sensing element is made in the form of two windings connected in opposite directions with different degrees of coupling with respect to to the magnetized winding,

connected to the moving coils of the specified compensating units, the output of one of which is directly, and the other through an amplifier connected to the corresponding inputs of the recording device.

On fvg. 1 shows a block diagram of the proposed device; in fig. 2 - a hysteresis loop of a ferromagnetic material in the field of weak fields (in the Relay region), illustrating the interdependence between the coercive force He, and the phase shift of the induction field B relative to the intensity of the field H; in fig. Figure 3 shows a vector diagram of currents, voltages, voltages, and magnetic field induction in the magnetizing winding.

The circuit (Fig. 1) contains the primary magnetizing winding 1, the secondary winding 2, closely connected with the primary, the secondary winding 3, weakly connected with the primary, ferrodynamic compensating blocks 4 and 5, fed by mutually orthogonal voltages, phase shifting circuit 6, the ballast resistor 7, the recording device 8, the amplifier 9.

FIG. 3 The following symbols are accepted: and is the EMF vector of self-induction of the magnetizing winding; r is the current vector of this winding; I am the vector of magnetic intensity

floor;

Phg - total magnetic flux; PV - magnetic flux in the air; E is the vector of EMF induced in the secondary winding 2 by the magnetic flux in the air;

2 - vector of EMF induced in the secondary winding 3 by the total magnetic flux;

Ey is an artificially derived vector, perpendicular to the vector and imitating the emf induced by the magnetic flux Fr;

EX, Ey are the elements of the expansion of the vector p in two orthogonal directions, one of which coincides with the direction of the magnetic field intensity vector.

Winding 2 and 3 are connected in series and counter and connected to the inputs of two compensating units 4 and 5, as shown in FIG. 1. Blocks 4 and 5 are powered by the voltage generated on the ballast resistor 7, the value of which is chosen so as to ensure the operation of blocks 4 and 5. The power supply voltage of block 5 is shifted by 90 ° with phase shifter 6. The outputs of blocks 4 and 5 are connected to registering device 8 (from block 4 - divisible, from block 5 - divider).

The scale of the device 8 is graded in units of coercive force — in Oersteds. Amplifier 9 is used to match devices 4 and 8.

The device works as follows. In the absence of material in the sensor (Fig. 3), the vector Fr is equal to zero, i.e. the vectors Fz and Fv are equal in magnitude and phase, and the voltage difference between the windings 2 and 3 is zero. Arrows

the ferrodynamic compensating units 4 and 5 are set to zero division.

When a material appears in the sensor (Fig. 1), the voltage of the winding 3 increases to a greater extent than the voltage of the winding 2. The vector Fr arises, and the difference in the voltage of the windings 2 and 3 becomes different from zero. The compensating blocks 4 and 5, by giving out the voltage E and Eu (Fig. 3), completely compensate the vector p and simultaneously measure its projections onto the orthogonal axes, one of which (block 4) coincides with the direction of the vector I. The device 8 automatically performs the division of the projections of the vector fp and registers the angle a:

arctg -. Hey

Increasing the sensor supply voltage increases the voltage of the windings 2 and

3, however, the position of the arrows of blocks 4 and 5 does not change, since at the same time the voltage drop on the ballast resistor 7 and, consequently, on the excitation windings of the compensating ferrodynamic blocks 4 and 5, increases.

Claims (1)

Invention Formula Device for measuring coercivity strengths of ferromagnetic materials containing a magnetizing winding connected to the input of a phase-shifting unit, a sensitive element, an amplifier and a recording device, characterized in that In order to increase the measurement accuracy, two ferrodynamic compensating units were additionally introduced in it, the excitation windings of one of which are connected to the input of the phase-shifting unit, and the excitation windings of the second - with its output, the sensitive element is made in the form of two oppositely connected windings with different degrees of coupling in relation to the magnetizing winding, connected to the moving coils of the indicated compensating units, the output of one of which is directly, and the other through the amplifier is connected to the corresponding conductive inputs of recording device. fjomoff o / neoL / a / o rr & AND f /one x jj 5 f & c: r ± n n 0 / - @, l Haf7 /} ff / KeHHOcmt, and