Analytical Model of Induction Machines with Multiple Cage Faults Using the Winding Tensor Approach

Abstract

Induction machines (IMs) are one of the main sources of mechanical power in many industrial processes, especially squirrel cage IMs (SCIMs), due to their robustness and reliability. Their sudden stoppage due to undetected faults may cause costly production breakdowns. One of the most frequent types of faults are cage faults (bar and end ring segment breakages), especially in motors that directly drive high-inertia loads (such as fans), in motors with frequent starts and stops, and in case of poorly manufactured cage windings. A continuous monitoring of IMs is needed to reduce this risk, integrated in plant-wide condition based maintenance (CBM) systems. Diverse diagnostic techniques have been proposed in the technical literature, either data-based, detecting fault-characteristic perturbations in the data collected from the IM, and model-based, observing the differences between the data collected from the actual IM and from its digital twin model. In both cases, fast and accurate IM models are needed to develop and optimize the fault diagnosis techniques. On the one hand, the finite elements approach can provide highly accurate models, but its computational cost and processing requirements are very high to be used in on-line fault diagnostic systems. On the other hand, analytical models can be much faster, but they can be very complex in case of highly asymmetrical machines, such as IMs with multiple cage faults. In this work, a new method is proposed for the analytical modelling of IMs with asymmetrical cage windings using a tensor based approach, which greatly reduces this complexity by applying routine tensor algebra to obtain the parameters of the faulty IM model from the healthy one. This winding tensor approach is explained theoretically and validated with the diagnosis of a commercial IM with multiple cage faults.

Low-Computational-Cost Hybrid FEM-Analytical Induction Machine Model for the Diagnosis of Rotor Eccentricity, Based on Sparse Identification Techniques and Trigonometric Interpolation

“…Following the same reasoning this method could be extended to other types of faults or even simultaneous faults, since the algorithm for computing the inductance matrix of the IM will compute the suitable terms to faithfully reproduce each type of fault. In the case of end ring-related faults can be simulated with the proposed model using simple tensor transformations from the starting resistance and inductance matrix, following the procedure proposed in [36].…”

Analytical Model of Eccentric Induction Machines Using the Conformal Winding Tensor Approach

“…It is worth mentioning that the set of loop currents used in Figure 3 is not unique. For example, in [36,38], another set of rotor loops currents has been used, with n b − 1 rotor loops containing a rotor bar and two loops for the currents in the rotor end-rings segments. As [47] states, they are simply different expressions of the current tensor, providing the same values for the actual bar and end-ring segment currents.…”

“…This is a cumbersome procedure [10], and a simplified model has been proposed in [10], replacing the actual bars of the cage rotor by an equivalent three-phase winding. A different proposal is the winding tensor approach (WTA), which replaces the coil by the conductor as the most basic unit and reduces the calculation process to routine tensor operations [36][37][38]. However, even the expression of the partial inductances between single conductors in eccentric IMs is a highly complex one [39].…”

Rotating Electrical Machines: Types, Applications and Recent Advances

“…Electrical Rotating Machines are the driven horses in power plants, construction, transportation, agriculture and automation sectors . REMs are the sources of mechanical power in industries because of their robustness and reliability (Martinez-Roman, et al, 2021). Electrical Machines can be broadly classified into Stationery and Rotational Electric Machines.…”