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| Figure 1 - Distortion of magnetic field power lines at (AGN): |
Figure 2 - Spatial coordinates of air- gap non-uniformity of the IM |
| (the given animations are disigned for 10 times recurrence) |
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Introduction
Most important problems of electric power industry are connected with reduction of energy losses and increase reliability of equipment operation. Both problems are manifests at occurrence of air-gap non-uniformity (AGN), arising in induction motors (IM). The specified phenomenon is caused abrasive deterioration of bearings, deformation of face boards of the machine, displacement of remote bearings, etc. As air-gap in the IM is rather small, the specified reasons cause rotor eccentricity and lead to vibration and accelerates deterioration of bearings.
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| Figure 1 - Distortion of magnetic field power lines at (AGN): |
Figure 2 - Spatial coordinates of air- gap non-uniformity of the IM |
| (the given animations are disigned for 10 times recurrence) |
|
Eccentricity is defined as a measure of infringement of air-gap symmetry by result of its direct measurings in face parts stator chisele under known formula
where 
- accordingly average and maximum sizes of an air-gap.
Because of relative small value of air-gap length this parameter is rather sensitive to deformation bearing boards and defects in bearings of the machine while in expluatation.
It is known, that as a result of occurrence significant eccentricity
the efficiency the IM decreases on 2,8 %, maximum and starting torque decrease within the limits of 20 % and 8 % accordingly, slip
increases for 10 %. In the heaviest cases is possible contact of a rotor with
internal stator surface. Damages arising at this demand
long regenerative repair of the IM. Expenses in this
case are comparable with cost of the new machine.
Absence effective ways of the indirect control of air-gap non-uniformity of asynchronous machines can be carried to
one of unresolved industrial problems. Perspective
direction in solving of the this problem is determination and use for
technical diagnostics criterial estimations of parametrical effect -
the phenomenon connected with dependence of air-gap non-uniformity from change of
inductive resistance of the machine.
Purposes and research problems
Purpose of work is research of the physical phenomena, reflecting effect of change of lekage fluxes outside of the case of the machine and influence of air-gap non-uniformity .
Primary goals of researches:
Scientific novelty
Existing techniques of estimation AGN are difficult, and demand measurment of phase currents and voltage of machines. The technique planned to development in work is based on registration AGN outside machine body during short-term switching-off from the power supply.
Existing techniques of the control of non-uniformity of an air-gap
It is necessary to note that direct measurment of AGN is difficult. In
practice should deal with non-uniformity in order of the tenth shares
millimeter, that means application ultraprecise measuring
devices. Thus AGN is defined by an electric axis of the machine (in practice
never in accuracy coincides with a geometrical axis of a rotor), that makes
practically impossible measurement of non-uniformity by measuring
devices.
To number of the most known methods of indirect AGN control are
measurment of synchronous inductive resistance value, and also measurment
value of inductive resistance of short circuit and zero sequence,
investigated at our university. To lacks of the specified methods follows
to carry:
Practical importance
Methods specified above have not found wide aplication in the industry. Thus, a problem of creation of more effective method control of AGN is actual.
Use of normal transient of short-term switching-off the IM as test influence can have essential advantage before known methods. Estimation of the efficiency investigated express -method requires determination of the machine's diagnostic parameter, choice of a probable diagnostic signal and estimation of its sensitivity to infringement of air-gap uniformity .
Purpose of the present work is development of diagnostic method, excluding the resulted lacks. This method will give theoretical conditions for development of the device for AGN control of all kinds of industrial machines. The given device will allow for several minutes of measurements and data processing to estimate AGN and take measures to elimination of non-uniformity. As already was marked above elimination AGN favorably affects to improvement of the general quantitieses of the electric machines.
Results of researches
At present work is not completed, yet. It is developed physical model of diagnosing AGN that requires experemental confirmation.
By present time the program of tests is made and experiment on the the equipment basis of DSTU "Common electrical machines" chair is lead. For measurements precision measuring analog digital device REKON - 08МС 
was used. Experience has been lead on the asynchronous machine of common application with rated voltage 380 V and power of 1,5 kW with purpose:
In experience during switching-off of the machine from a network, were recived dependences of a voltage in stator lekage fluxes of the machine 
.
Carrying out experements on the machine with opportunity changing ofAGN is planned on the end of may 2007.
Conclusion
At writing the given abstract master's work is not completed yet. The full text of work and all materials on a theme can be received from author or his head after end of researches in IV quarter 2007.
