RU2240564C2 - Method for measuring sliding of asynchronous engines - Google Patents

Abstract

FIELD: measuring equipment engineering.

SUBSTANCE: method includes use of constant voltage signal as information signal, which is scaled, inverted and than added to bearing voltage signal, value of which is determined during synchronous rotation, received total is amplified until it is useable for measurement, than sliding of asynchronous engine is measured on basis of measured value.

EFFECT: higher interference resistance, higher precision, shorter time delay, possible automated process.

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Description

The invention relates to the field of automation and measurement technology. The invention solves the problem of automation of industrial testing of induction motors (AM) and electric drives (EP) based on them, improves the quality of tests.

There is a known method of a direct current ammeter, which assumes the use of a direct current ammeter and a shunt introduced into one of the rotor phases for measuring the rotor current frequency (see Gervais G.K. Industrial tests of electric machines. - 4th ed., Abbr. And rev. - L .: Energoatomizdat. Leningrad branch, 1984), used only for blood pressure with a phase rotor and constantly overlapping brushes. The rotor frequency f _{2 is} calculated as the ratio of the number of total oscillations of the arrow of the device to the period of time during which these oscillations were made:

where N is the number of full oscillations of the arrow;

t is the period of time during which the oscillations were made.

The slip value s is determined by the ratio of the frequencies of the rotor and stator:

where f ₁ is the frequency of the stator current HELL.

The disadvantage is that this method cannot be applied when testing blood pressure with a squirrel-cage rotor, as well as the need to measure the frequency of the power supply of blood pressure with an additional device.

Closest to the proposed essentially and the problem being solved is a method involving the use of a discharge lamp to create a stroboscopic effect (see Gervais G.K. Industrial tests of electric machines. - 4th ed., Abbr. And revised. - L.: Energoatomizdat Leningrad, Department, 1984). The stroboscopic effect is obtained by illuminating a disk with black sectors at the shaft end of the tested machine with a discharge lamp. The number of blackened sectors depends on the pole of the machine. The gas discharge lamp is connected to the power supply of blood pressure. Sliding s is found as the ratio of twice the number of revolutions of the disk when illuminated by a gas discharge lamp to the period of time during which the blackened disk made revolutions.

where N is the number of revolutions of the disk with black sectors;

t is the period of time for which the revolutions were counted.

The disadvantage of this method is that for the measurement to take some time, which can be 10-15 s, during this time the rotor of the tested blood pressure heats up during tests in overload mode, as well as when testing engines with a large amount of slip, which leads to a change slip values during slip measurement, which in turn leads to errors in slip measurement. The disadvantages is that with a large amount of slip there are difficulties in counting the revolutions of the blackened disk, which also affects the accuracy of the result.

The problem solved by the invention is to increase noise immunity, measurement accuracy, reduce the time for measurement and the ability to automate the process of testing blood pressure.

The solution to this problem is achieved by using a constant voltage signal as an information signal, which is scaled, inverted, and then added to the reference voltage signal, the value of which is determined by synchronous rotation, the resulting sum is amplified to a value suitable for measurement, measured and measured value determine the slip of an induction motor.

Compared with the closest analogue, the claimed solution has distinctive features:

- use as a signal - a constant voltage signal;

- use as a reference signal of a constant voltage, determined during synchronous rotation of the shaft of the tested blood pressure;

- the use of a DC voltage converter with the Hall effect;

- application of the operation of analog summation.

When using the proposed method, the noise immunity is increased, which is due to the use of a constant voltage signal as an information signal, the time required to perform a slip measurement is reduced by using an adder of analog signals.

An example of the implementation of the proposed method is a device, a block diagram of which is illustrated in the drawing, which shows a device for measuring slip, containing a speed sensor 1, a DC voltage transducer with Hall effect 2, an inverting amplifier 3, an analog adder 4, an output signal amplifier 5.

The method of measuring the AD slip consists in the following actions: the speed sensor 1 converts the rotational speed of the AD n shaft to the voltage U _TG , the signal U _{TG is} scaled by the DC voltage converter 2. From the output of the converter, the signal U _{DC is} fed to the inverting amplifier 3, then to the first input of the adder 4 The second input of the adder 4 is supplied with a reference voltage U of the _supports , the value of which is determined by synchronous rotation of the HELL shaft so that the output voltage of the adder U ₁ tends to zero on the right. The output voltage of the adder is fed to the input of the output amplifier 5, which is then measured using a DC voltmeter.

The amount of slip is determined by the formula

where k ₂ is the gain of the output amplifier,

U ₂ - voltage measured by a DC voltmeter.

In this case, the value of the reference voltage U of the _{supports is} set at

synchronous rotation of the test machine so that the condition

and when testing the blood pressure is fed to the second input of the adder of analog signals.

The gain of the output amplifier is selected so that the voltage U _{2 is} in the range from 35 to 95% of the scale of the device measuring U ₂ , or from 35 to 95% of the maximum voltage measured by an analog-to-digital converter that performs the functions of a voltmeter.

Noise immunity is achieved by using a constant voltage signal as an information signal. The measurement accuracy is achieved due to the operation on the information signal at the analog level, due to the measurement error U ₂ , the accuracy of the reference voltage U of the _supports and is determined by the formula

Using the proposed method for industrial testing of blood pressure allows you to automate the test process, to increase the noise immunity and accuracy of measurement of the magnitude of the slip.

Claims (1)

A method of measuring the slip of induction motors, characterized in that a DC voltage signal is used as an information signal from a speed sensor that converts the rotational speed of the shaft of an induction motor to a constant voltage, which is scaled by a Hall-effect DC / DC converter, invert by applying a signal to the inverting input an adder, after which the summed signal with a reference voltage U _SUPPORTS, which value is determined at synchronous rotation shaft ispytue th induction motor so that the output voltage of the adder tend to zero on the right, and is supplied to the noninverting input of the adder whose output voltage is fed to the output amplifier input, then measured using a DC voltmeter, and determining the slip by the formula s induction motor s = [U ₂ / (k ₂ · U _SUPPORT )] 100%, where k ₂ is the gain of the output amplifier, U ₂ is the voltage measured by a DC voltmeter.