Kovalenko M.A., Ph.D. in Technical Sciences., assistant; Pelypenko K.O., student.

National Technical University of Ukraine «Kyiv Polytechnic Institute»

The development of three-dimensional math model of inductive diagnosis system for induction motors with centrifugal production method

Introduction. Nowadays Electrical Repair services are applying «visual» diagnosis of rotor damages in the process of the Induction Motor (IM) repairing. Usually this process contains rotor overview and without visible damages being identified one continues to use the rotor as a component of renovated IM. However, such practice does not meet the modern requirements for providing reliable work of repaired electrical equipment because of the frequent cases of motor breakdown after short-term use; it can be related with the damaged stator winding, caused by work with faulty squirrel cage (or short-circuited rotor winding).

With the centrifugal method of rotor production, rod resistance has anisotropic properties and during inductive diagnosis, rotor inaccuracies may be encountered.

Aim of work. The purpose is the development of math model of system, which is called «The IM rotor as an inductive device», and the research of diagnostic features with the use of centrifugal and static methods of a squirrel cage production.

Materials and research results. In this work a three-dimensional math model of inductive devise has been developed, as it is shown on the figure 1 (a): 1 – rotor under investigation, 2 – magnetic core of inductor, 3 – measurement winding (MW), 4 – excitation winding (EW). The model is numerically implemented in COMSOL Multiphysics 4.4 pack.

The damage of squirrel cage rods is represented with conductivity decrease in rod material, in extreme case it`s conductivity is equal to zero during the collapse of rod.

The EMF of measurement winding is calculated by the value, attached to a resulting magnetic flux of MW:

(1)

_{Where Bn – normal component of magnetic induction at MW surface area, WMW – number of turns on MW, SMW – surface area with MW placed in;}

_{In the case of spinning anisotropic properties of rods material in the investigated rotor are simulated as follows:}

(2)

_{where – aluminium electrical conductivity; x, y – Cartesian coordinates.}

_{Inner cracks in the rod of squirrel-cage rotor and inner cavernes were analysed.}

_{Figure 1 (b) shows the distribution of conductivity throughout the height of slot with the use of spinning in the motor 4A112M4Y3.}

_{a) b)}

_{Fig. 1 – calculated system area}

_{Figure 2 is the dependency graphs of crack hights 2 (a) and cavern areas 2 (b) and their dependence on multiple Ke for both static and centrifugal methods.}

_{a) b)}

_{Fig. 2}

_{Conclusion: designed math model should be used for methodological support for fault detection systems. They may find defects of squirrel cage rotors in IM with different methods of priming.}

_References

_{1. Vaskovski U. M. Field analysis of electric machines: Teaching Manual – K.: NTUU «KPI», 2007 – 192 c.}

_{2. Taran V. P. Diagnostical electric equipment – K.: Machinery, 1983. – 200 c.}