SU892373A1 - Device for measuring ac machine magnetic flux vector rotation speed - Google Patents

Description

(B) DEVICE FOR MEASURING ROTATION FREQUENCY

VECTOR MAGNETIC FLOW OF A VARIABLE MACHINE

I

The invention relates to a frequency-controlled electric drive and can be used in frequency-controlled drives to obtain signals proportional to the frequency of rotation. Neither vector of magnetic flux, which can be used in the AC machine control system.

The known device consists of a measuring coil located on the stator, an integrator, a phase detector, a filter, a controlled oscillator. The output of the measuring kagtushki is connected to the input of the integrator, the output of which is connected to one input of the phase detector, to the other input of which a signal is supplied from the controlled oscillator. The output of the phase detector is connected to the input of a filter, the output of which is connected to the input of a controlled oscillator. The signal from the measuring coil is integrated and in the phase detector compares the current

With the signal received from the controlled signal. If the phase of the controlled oscillator does not correspond to the phase of the integrator signal, then a signal proportional to the phase mismatch is fed through the filter to the input of the controlled oscillator and corrects its frequency. The signal at the input of the controlled oscillator can determine the frequency of the signal at the output of this

10 generator, and hence the frequency of the signal at the output of the integrator, i.e. the frequency of the measured magnetic flux Cl 3.

However, this method of measuring the frequency of the magnetic flux relies on a rather complex element base, since the controlled oscillator is a rather complicated device, and the known system is also inertial because it contains a filter. The reorganization of the controlled oscillator from one frequency to another takes place at a finite time interval. With

This range of measured frequencies is determined by the working frequency range of the controlled oscillator, which limits the capabilities of the device.

The purpose of the invention is to increase the speed and expand the range of measured frequencies.

The goal is achieved by the fact that the device for measuring the rotational frequency of the magnetic flux vector of an alternating current machine, containing a measuring coil and an integrator connected in series, is equipped with a second measuring coil and a second integrator, the first and second production units, a division unit, adder, square module calculator, moreover, the outputs of the first and second integrators are connected respectively to the first inputs of the first and second blocks of the product and the inputs you the numerator of the square of the module, the output of which is connected to the first input of the dividing unit, the second input of the last one is connected to the Output of the adder, the first and second inputs of which are connected respectively to the outputs of the first and second production blocks, the second inputs of which are connected respectively to the first and second measuring coils. The drawing shows a block diagram of the device. A device for measuring the frequency of rotation of the magnetic flux vector of an asynchronous machine consists of measuring coils 1 and 2, integrators 3 and i blocks 5 and 6 of the product, adder 7, block 8 dividing units, calculator 9 squared module. The outputs of the measuring coils 1 and 2 are connected to the inputs of the integrators 3 and k, as well as to the inputs of blocks 5 and 6 of the product. The outputs of the integrators 3 and connected to other inputs of blocks 5 and 6 of the product, as well as to the inputs of the transmitter 9 square module. The outputs of blocks 5 and 6 of the product are connected to the inputs of the adder 7. The output of the adder 7 and the output of the calculator 9 of the square module are connected to the inputs of the division unit 8, the output of which produces a signal J proportional to the frequency of rotation of the magnetic flux vector. The device works as follows. In coils 1 and 2, which are located on the stator of the asynchronous machine

relative to each other at an angle of 90 electrical degrees, are induced emf proportional to the derivative of magnetic fluxes along the corresponding axes m.

Thus, the signal received from the measuring coils 1 and 2 is proportional to the product of the amplitude of the magnetic flux, the frequency of rotation of the magnetic flux vector and the law of measurement of this flux over time. Thus, the signal received from the measuring coils 1 and 2 contains information about the frequency of rotation of the magnetic flux vector.

Integrating this signal by integrators 3 and t, we get a signal that determines the law of change of the magnetic flux. Finding the square of the modulus of this signal in the calculator 9 determines the signal proportional only to the square of the amplitude of the magnetic flux. B-adder 7 summarizes the signals proportional to the products of the magnetic flux along one axis, to the derivative of the magnetic flux along the other axis. We receive these signals using blocks 5 and 6 of the product. This makes it possible to obtain at the output of the adder 7 a signal which depends only on the product of the frequency of rotation of the magnetic flux vector and the square of the amplitude of the magnetic flux. The use of (- the signal output by the calculator 9 of the square of the flow module) is obtained at the output of dividing unit 8 a signal proportional to the instantaneous frequency of rotation of the magnetic flux vector. The invention can be used to study the magnetic field of an AC machine, as well as to build a frequency control system The use of the device will improve the speed of the drive and the accuracy of its operation. Accuracy is determined by the accuracy class of the blocks used, and when sse accuracy not worse than 0.2 U, which is quite acceptable for technical measurement. Since the device have filters and delay the result will be dispensed immediately, while the delay is measured in the known device is determined by the time constant of the filter.

Claims (1)

Invention Formula A device for measuring the frequency of rotation of the magnetic flux vector of an alternating current machine, comprising a measuring coil and an integrator connected in series, characterized in that, in order to increase speed and expand the range of measured frequencies, it is equipped with a second measuring coil and a second integrator connected in series, first and the second product block, the division unit, the adder, the unit square calculator, and the outputs of the first and second integrators are connected respectively the first inputs of the first and second blocks of the product and the inputs of the calculator of the squared module, the output of which is connected to the first input of the division unit, the second input of the last is connected to the output of the adder, the first and second inputs of which are connected respectively to the outputs of the first and second blocks of the product, the second inputs of which are connected respectively to the first and second measuring coils. Sources of information taken into account in the examination 1, US Patent Vt, Cl. H 02 R 5LO, 1977.