SU1755038A1 - Method for checking fodder crusher motors - Google Patents

Abstract

Usage: in agriculture, in particular to monitor the performance of feed crushers. Summary of the invention: in order to simplify the monitoring process without disconnecting the engine from the working machine, the instantaneous values of phase electromotive forces and their amounts are simultaneously measured, and the unevenness of the air gap is determined by the formula given in the description text.

Description

This invention relates to the field of agriculture, in particular to methods for monitoring the performance of feed crushers.

A known method for controlling the air gap non-uniformity of asynchronous machines, according to which the AC voltage is applied to the terminals of the test machine, continuously increasing it until the machine starts rotating, in order to determine the degree of air gap non-uniformity by the amount of moving voltage. accurate, since the voltage of the moving electric machine depends on the position of the rotor.

A known method of indirect control of the unevenness of the air gap, according to which, by means of an auxiliary engine, synchronously rotates the rotor of the controlled electric machine, a voltage is applied to one of the phases. The voltages induced in the remaining two phases are compared, the voltage is disconnected from the first phase, is fed to the second phase, and

induced in the other two phases of the voltage. The process is repeated for the third phase and by the detected maximum difference between the voltages in the phases, an uneven air gap is judged,

This method of control is not accurate enough due to the effects of voltage fluctuations in the network and the spread of the engine transformation ratio due to the asymmetry of the magnetic field.

In order to measure the degree of unevenness of the air gap of the crusher electric motor in this way, it is necessary to carry out the following operations sequentially: disconnect the engine from the crusher and remove it from the workplace; under the conditions of a specialized workshop, disassemble the engine and measure the air gap unevenness with calibrated probes.

This method requires a lot of labor, the availability of special equipment and highly qualified staff, while having a high degree of error of measurement.

shaA

neither Its use causes prolonged downtime crushers.

The aim of the invention is to simplify the process of monitoring the non-uniformity of the air gap of three-phase asynchronous electric motors of crushers by carrying out all measurements at the time of the motor run, which allows monitoring of the air gap, not disconnecting the controlled electric motor from the crusher

The goal is achieved by the fact that in the method of indirect control of the unevenness of the air gap of three-phase asynchronous electric motors of crushers, which consists in acceleration of the controlled electric motor by switching it on, disconnecting from the network and measuring at the time of the overrun, different EMF EF and total EMF CE induced by the residual magnetic field of the rotir in all three stator windings, the obtained values of HE and Ef are simultaneously inserted into the formula

: Wed

switching off the electric motor from the network and remains on the rotor unchanged for quite a long time (about 6-8 months). The strength of this residual field depends only on the magnetizing component of the current, which in turn depends only on the voltage. Those. for electric motors, the residual magnetic field of the rotor will be the same regardless of the load that they experienced during connection to the network. Immediately after disconnecting the electric motor 1 from the network, a millivoltmeter 3 is connected to the stator windings, as shown in Figures 1 and 2, and a tachometer 2 is turned on, which records the instantaneous value of the total emf (E) induced in the stator windings by the residual rotor magnetic field and rotation frequency rotor of expression

Ef 4.44 KOKU f F, (1)

It follows that, taking into account the eccentricity of the rotor, the phasic emf induced in the stator winding

Ef 4.44 Koiw f Fost, (2)

insofar as

where e is the eccentricity;

ЈE is the measured instantaneous value of the total emf induced in the stator windings by the residual magnetic field of the rotor;

ECP "previously measured

the value of the average EMF induced in the stator windings by the residual magnetic field of the rotor;

Kp is a coefficient taking into account the number of poles of a given electric motor and judging by the value obtained, the air gap is uneven.

FIG. 1 shows a diagram of a method for the spontaneous monitoring of the air gap unevenness for an engine whose windings are connected in a star; figure 2 is a motor whose windings are connected in delta; Fig. 3 is a diagram of the position of an eccentric biased rotor in the stator bore.

The circuits contain a controlled asynchronous engine crusher 1, to which a tachometer 2 and millivoltmeter 3 are connected.

The controlled engine 1 of the crusher is switched on to the network, after which it starts to accelerate to a speed that ensures optimal operation of the working bodies of the drive axles. In a period of time, a constant magnetic field is created on the rotor by the stator windings, which remains after - Howling.

Fost l-ЈCosa

t

Fo

ICT

1 -ecosa

(3)

where fost is the magnetic flux;

Howls - the average value of the induction curve of the floor; r-pole division;

I - active conductor length;}

in - eccentricity.

Follows that

R"

ЕФ Т 7Ь777 Е ° 0 + есо8а), W

 e cos a where Ео - the average value of the phase emf

45

Yeo

 Unit + ev + her

(five)

50

where Ed; Ev; Her - EMF phases A, B, C

The result of the expression 4 eccentricity is:

  Emax Ep

tiQ -.

(6)

where Emax is the maximum value of the EMF of one of the phases induced by the residual magnetic field of the rotor in the stator windings.

Insofar as

Un Em (1 + e) sin ai,

Eu ET (1 - Ј / 2) sin (wt + 120 °), Ec Em (1 - E II) sin (a) t-120 °,

then you can write

Е ЕА + Ев + Ес Ет (1 + Ј) sin (О 1+; + (1-Е / 2)

(slrvft)) + (1.g / 2) x

x (-Sl2nm -C05) Et (1 + Ј) x

 H

x sin + (1 - e / 2) x (sin ft) t) -UETX

xsinft t Ј. „(7)

From the expression 7 it is seen that for two

total engine dependence

The emf from the eccentricity will be as follows:

ЈЕ; - | GET sinu) t Ј -2Yj JS Е,

Esr or

(eight)

where Cros - coefficient taking into account the number of pairs of poles of the engine;

Cr 1.06 for a bipolar motor; ЈE-total emf induced in the stator windings by the residual magnetic field of the rotor;

Э eccentricity;

 -. ЕА + ЕВ + Ес t -

: Wed

measured 35

the value of the average EMF induced in the stator windings by the residual magnetic lift-: rotor .., ..., l,;.

From here Ј Kr

-sr

where Kp - coefficient taking into account the number of pole pairs of the electric motor.

EXAMPLE 1. A controlled asynchronous 4A80A2UZ engine of the crusher is turned on and accelerated. After that, the motor 1 is disconnected from the network and a millivoltmeter 3 is connected to its windings, as shown in Figures 1 and 2. At millivoltmeter 3, an indication appears: E 1.36V. The previously measured value Ef 1.92 V. We substitute these values into the formula

Ј Cr

: Wed

0.94- -If- -0.67.

;

x

tx

(7)

drink

Noah

her:

and

sh

Yu

15

20

8) 25

lay

l; circumference-:., l,;.

thirty

Noe 35

40

lay

nkhlki tolyuk as she ta45

50

55

With this motor, the eccentricity of the rotor is Ј 0.67.-. Thus, the measurement of the air gap non-uniformity value exceeds the normalized value of 0.1 by 6.7 times, which allows determining the malfunction that has occurred.

The use of the proposed method will provide the following advantages for the Sranenito prototype: it is possible to control the non-uniformity of the air gap not disconnecting the controlled motor from the crusher, since all measurements are made at the time of the rotor run-down; the measurement time is reduced, since the measured parameters are recorded at the same time; the number of operations is reduced, since the number of switchings in this method can be reduced to two: turn on the engine in the network; disconnect the motor from the network and connect the millivoltmeter. The value of the total emf induced by the residual magnetic field of the rotor in the stator windings has not been previously used in methods for monitoring the air gap non-uniformity.

Claims (1)

. Invention Formula The method of monitoring the condition of the electric motors of the feed crushers, including the forced rotation of the working bodies and the measurement of the EMF induced by the magnetic flux of the rotor, so that they have been turned off. that, in order to simplify the monitoring process without disconnecting the engine from the working machine, the instantaneous values of the phase emf are simultaneously measured, their sums are calculated, and the air gap irregularity Ј is determined by the formula e MЈEf / Esr),,, -  - the value of the total emf; Кр0- coefficient. taking into account the number of pairs of poles of electric motors; ESR (U + U + U); 3 is the value of the average emf. induced by rotor residual magnetic paddle in the stator windings. 1 2 ShGZ