Study of Eccentricity in a Machine Three-Phase Induction Squirrel-Cage Rotor

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As you can see in Figure 1, the field lines feature a regular layout, i.e. not present discontinuities nor is there a great density in terms of field as shown. Once a there is no discontinuity points, it can be concluded that the finite element mesh set fits problem. Another aspect is the fact that the field lines don't go out of bounds are representative of the machine, which shows that the boundaries are well defined (Dirichelet).

[pic 3]

Figure 1-centered Rotor; FEMM model

- Choice of material

The windings estatóricos material is Winding Stator windings surround material estatóricos and rotóricas bars of M-15 steel material. Rotóricas bars material is Alumium and the spindle of the machine and the air gap is Air table 2 [6].

B- Sizing of conductors

Sizing of conductors estatóricos windings. In the scaling of these drivers is important to know some aspects, such as: total area of cava, cava's useful floor area, number of turns for cava, among others. Knowing that each cava possessed a total area of 5.74609 x 10-5 m2, it is possible to know which area of the same. To determine this aspect, it is considered that the area is about 75% of the total area. With this, an area of about 4 x 10-5 m2. Each dig a total of 44 turns and knowing the value of the area, a section of approximately 0.979 mm2/espira. Using a table of a manufacturer of enamelled copper conductors, it was found that the effective current permissible by the driver is 1.89, corresponding to a conductor AWG 17. Once the FEMM only works with maximum currents, the current used in the simulation was of (√ 2 × 1.89) = 2.67A.

17 AWG copper conductor based on the manufacturer's catalogue and the calculations performed [4].

III. Simulation process

After the completion of the modelling machine for eccentricity regimes, we opted for the implementation of programming in form. "Lua" in the whole process to make, in order to achieve greater convenience in obtaining results, so you can proceed to the simulation of a simpler way. Thus, FEMM application in the process of obtaining the results (in programming. "Lua") [7].

For a better observation of the results of the simulations to perform opted for creating a file "results.txt" which will contain the values of slipping and electric torque corresponding the tables presented. Later, making the treatment of them can get the curves T = f (s) of accompanying figures [6].

A simulation where the goal was to remove the torque produced by the machine fig. 4, being centered rotor was necessary to alter conductivity (G = 34.5 MS/m) of aluminium rotor bars in order to simulate the current rotóricas GS = G ' in table 2 and being stator constant current and so determine for each slip (s) the torque (T) appropriate and was not used by frequency because it would be another study where frotor = festator x s With this was obtained the results of Table 2.

IV. Results and analysis

In this chapter will be presented the results obtained through the various simulations performed. The following results were obtained for the position of static, dynamic and mixed regime that you can see in the attached tables and figures:[pic 4]

- Figure 2- (a) static Regime, (b) dynamic Regime, (c) mixed Regime

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- A- Analysis of eccentricity for different topologies fig. 3.

Static position for the analysis of table 2 and graph-centered rotor fig. 4.

Table 2-results obtained for the simulations conducted for the rotor machine centered

s

G'=G x s

T

0

0

0,046122

0,1

3,45

0,034209

0,2

6,9

0,046056

0,3

10,35

0,022536

0,4

13,8

0,01455

0,5

17,25

0,010624

0,6

20,7

0,006655

0,7

24,15

0,005525

0,8

27,6

0,004682

0,9

31,05

0,004682

1

34,5

0,00403

[pic 5]

Figure 4 -graphical representation of the results obtained for the simulations conducted for the rotor machine centered You = f (ω (%)).

- Static regime.

Rotor centered on analysis that will serve as compared to several studies of eccentricity at offset axis xx in that it displaces 25% and 75% in .50% air gap (air gap) fig. 3 and the verification of the binary in table 3 and the air gap value is 0.375 mm:

- Rotor centered – figure 2-(a);

- The 25% off center rotor air gap;

- The 50% off center rotor air gap;

- Rotor off center to 75% air gap;

[pic 6]

Figure 3-static regime with offset axis rotor xx

Table