Anna-Kaisa Repo

Small-Signal Modelling of Saturated Induction Machines With Closed or Skewed Rotor Slots

A small-signal model is derived for saturated induction machines. Inductances are allowed to saturate as a function of their own current (or flux), and the mutual saturation effect originating mainly from skewed or closed rotor slots is also included in the model. The model fulfills the reciprocity conditions, and it can be applied to parameter identification and to the analysis and development of flux angle estimation methods. As an example, the model is applied to parameter identification, using the data from time-stepping finite-element analysis.

Inclusion of hysteresis and eddy current losses in dynamic induction machine models

This paper proposes a method for including both hysteresis losses and eddy current losses in the dynamic space vector model of induction machines. The losses caused by the rotation and magnitude changes of the flux vector are taken into account. The model can be applied, for example, to time-domain simulations and real-time applications such as drive control. Finite element analysis, simulations, and laboratory experiments of a 45-kW motor are used for the investigation. It is shown that the model can predict the iron losses in a wide frequency range. The accuracy is significantly improved as compared to earlier models.

Small-Signal Modeling of Mutual Saturation in Induction Machines

A small-signal model is derived for saturated induction machines. Inductances are allowed to saturate as a function of their own current (or flux), and the mutual saturation effect originating mainly from skewed or closed rotor slots is also included in the model. The model fulfills the reciprocity conditions, and it can be applied to parameter identification and to the analysis and development of flux-angle estimation methods. As application examples, the parameters of a 2.2-kW induction machine were identified using the data obtained from time-stepping finite-element analysis and locked-rotor measurements. The proposed model fits well to the data, and the fitted parameters are physically reasonable.

Identification of Electromagnetic Torque Model for Induction Machines With Numerical Magnetic Field Solution

In this paper, the identification of a parametric electromagnetic torque model for induction machines is studied. The data for the identification procedure is provided by the numerical impulse response test performed within a 2-D time-stepping finite-element analysis (FEA). The parametric models are obtained from the theory of electric machines. The parameters are estimated using the data obtained from the numerical field solution. Within the impulse test, an assumption of linear behavior in the neighborhood of an operation point is made. As the real electric machine is a nonlinear, time-variant system, the applicability of the impulse test is studied by several means.

Parameter estimation for induction motors to study the effects of voltage, frequency and slip

Parameter estimation for cage-induction machines is studied by means of 2D finite-element (FE) computations. The estimation methods are based on the time-harmonic and time-stepping FE analyses. The parameters are estimated in a wide operation range. The main purpose of the paper is to study how the steady-state and small-signal parameters vary in the case of a cage-induction machine designed for a frequency converter supply. The estimation is performed at 13 different supply frequencies. At every frequency, several flux levels are studied. Slips that provide the best efficiency are looked for and the parameters are estimated at these points. For comparison, the parameters of a typical grid-supplied cage-induction machine are also estimated at several slips and flux levels.

Parameter estimation for synchronous machines using numerical pulse test within finite element analysis

This study aims to estimate equivalent circuit parameters for a synchronous machine. The need for equivalent circuits rises from practical applications. Accurate models are needed for control design and power system analysis. The research was conducted using the 2D finite element analysis and the differential evolution algorithm. As an input to the synchronous machine, a pulse is used within the FEA at the rated operation point. The pulse was applied to the line-to-line voltage of the stator. Using the pulse input, the harmonic excitation can be avoided. The input in addition to the response provided the numerical data for estimation. On one hand, theoretical equations based on the equivalent circuits can be derived. The theoretical model was fitted in the numerical data using the least-squares cost formulation, and the DE algorithm was used to minimize the cost function. Results for a 6-pole, 12.5 MW synchronous machine are presented.

Small-signal model for saturated deep-bar induction machines

A small-signal model is presented for saturated deep-bar induction machines. Inductances are allowed to saturate as a function of their own current (or flux), and the mutual saturation effect originating mainly from closed or skewed rotor slots is also included in the model. The model fulfills the reciprocity conditions, and it can applied to parameter estimation and to the analysis and development of flux angle estimation methods. The model is applied to estimating the parameters of a 37-kW deep-bar cage-induction machine, using the data from time-stepping finite-element analysis (FEA). The proposed model fits very well to the FEA data in a wide frequency range.

Parameter estimation of induction machines using the numerical impulse method

A new method for estimating the small-signal parameters of induction machines is presented. The data for estimation is produced by two-dimensional time-stepping finite element analysis (FEA). The method is applied to three different types of induction machines: a cage-induction, solid-rotor and slip-ring machine. The steady-state parameters of the induction machines are also estimated. This estimation is based on the time-harmonic FEA. The fitting results are good and the estimated parameters are physically reasonable

Parameter estimation of synchronous machines by using the Differential Evolution algorithm

This paper is aiming at presenting parameter estimation using the Differential Evolution algorithm. Previously, evolution based algorithms has been applied to frequency domain data. Within this study, the Differential Evolution algorithm has been applied to time-domain data. Convergence of this estimation procedure, presented within this paper, is validated by using synthetic data. Results obtained are presented, and especially, the effect of the length of the excitation signal and convergence differencies between distinct runs are compared. Due to the stochastic nature of the DE algorithm, it can not be said exactly how many iteration round are needed. However, based on the results obtained within this study, it can be said that the parameters were found in 300 iterations.

Permanent magnet assisted synchronous reluctance motor in hoist application

A permanent magnet assisted synchronous reluctance (PMASR) motor is designed and tested for a wire rope hoist for which the load and speed requirements vary greatly especially in workshop usage. The new hoisting motor is compared with the state-of-art cage-induction motor. The advantages of PMASR motor in hoist application are a high torque at low speeds, wide speed range, reasonable back EMF, and high torque/current ratio. Different rotor geometries are designed and the performance is analyzed using time-discretized numerical analysis. The main design criterion is minimizing the amount of permanent-magnet material. The experimental results verify that the PMASR motor is suitable for hoisting applications.