Coupled Fluid-Thermal Analysis for Induction Motors with Broken Bars Operating under the Rated Load

This article discusses the thermal and mechanical exposure of the starting cage of a double-cage induction motor rotor during start-up. Damage to the starting cage is the most common cause of failure of a double-cage winding during long start-ups. It has been indicated that the end region of the double-cage winding is a key area in the search for a more damage-resistant solution. Among the available studies on improving the mechanical strength of double-cage windings, which typically focuses on improving the cooling system, modifying the shape of the slots, or altering the bar material, a new concept of improving the mechanical strength through the modification of the structure of the end region has appeared. This is achieved by applying sleeves onto the ends of the starting cage bars, which helps to reduce the temperature of the connection between the starting bars and the end rings. A simulation of the temperature field of a double-cage induction motor with this new design is performed and discussed in this paper. It has been confirmed that the new design solution effectively improves the mechanical strength of the starting cage, making it less prone to damage caused by thermal stresses.

Section: Methods Of Analysing the Temperature Field Of A Double-cage Imentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Improvement of the Thermal and Mechanical Strength of the Starting Cage of Double-Cage Induction Motors

Mróz

Poprawski

2019

“…There are many magnetic poles of the Three Gorges hydro-generator, and the rotor magnetic pole structure is relatively complex. Limited by the calculation capacity of the simulation equipment, in order to ensure the accurate calculation of magnetic pole thermal stress, it is necessary to reasonably simplify the rotor solution domain and establish the calculation model of a single magnetic pole, shown in Figure 1, where the assumptions are as follows [18][19][20][21][22]. (1) The calculation model for one magnetic pole of the hydro-generator is established given that all rotor magnetic poles and wind paths of the hydro-generator are symmetrical.…”

Section: Physical Modelmentioning

confidence: 99%

Calculation and Analysis of Rotor Thermal Static Field for Inter-Turn Short Circuit of Large Hydro-Generator Excitation Winding

Wang

2019

Rotor winding inter-turn short circuit a common fault in hydro-generators. This fault would change the temperature, stress, and other thermal fields of a rotor and threaten the safe operation of the generator. In this paper, the Three Gorges hydro-generator is taken as an example. Mathematical models of three-dimensional temperature field and thermal stress field of rotor magnetic poles are established based on heat transfer theory and solved by finite element method. The temperature field, thermal deformation, and thermal stress distribution of magnetic poles in rotor winding inter-turn short circuit are calculated. On the basis of the calculation, the effects of the different turn numbers and positions of short circuit on the temperature, thermal deformation, and thermal stress of rotor magnetic poles are further studied. It is concluded that the thermal stress of the winding adjacent to the shorted turn would decrease, the thermal stress of the winding farther away from the shorted winding would increase, and so on. The results of this paper can provide references for inter-turn short circuit fault diagnosis and lay a foundation for the further studies of related faults.

“…It is vital to accurately judge the generator aging by calculating the temperature distribution under main insulation normal operation and fault operation. In addition, the calculation and analysis of temperature fields are often applied in research fields, such as induction motors and permanent magnet motors [29][30][31][32][33]. Therefore, the change in generator temperature and stress fields after fault are important fault features that are worthy of study.…”

Section: Introductionmentioning

confidence: 99%

Multifield Calculation and Analysis of Excitation Winding Interturn Short Circuit Fault in Turbo-Generator

et al. 2018

Excitation winding interturn short circuit (EWISC) is a common fault in turbo-generators. Once the fault occurs, if not handled in time, it will result in significant security risks to the power system. Using the multifield characteristics of fault generators for a comprehensive diagnosis can make the diagnostic results more accurate and credible. In this paper, taking a TA-1100-78 type, two pole pairs turbo-generator as the research object, the two-dimensional finite element electromagnetic model of stator/rotor and the three-dimensional finite element heat transfer model of rotor were established. The electromagnetic field, temperature field, and stress field of the generator were simulated and analyzed. At the same time, the air gap magnetic field, three-dimensional temperature field, and stress field distribution of the rotor were calculated for EWISC faults in different fault degrees and positions. The results showed that the EWISC fault weakened the air gap magnetic field and caused unbalanced electromagnetic distribution. At the same time, it caused a distortion of the rotor temperature field, resulting in an unbalanced distribution of the temperature field. The stress field was affected by the distortion of temperature field, and the local thermal stress increased but did not exceed the yield limit of the material. Restorable elastic deformation occurred when the rotor was heated, which caused the thermal bending of the rotor. The method adopted in this paper can provide a reference for the calculation of multiphysical field after a generator fault. It is also pointed out that the thermal unbalance influence should not be neglected in the study of generator vibration characteristics.