Aurel Campeanu

Aspects regarding optimal design of high power squirrel cage asynchronous motors

The lately important development of some high precision electrical drives with great response speed, as well as the fact that the electrical machines exploitation is closer and closer to limit of stability have led to intense preoccupations, in the whole world and in our country, for the precise determination of the asynchronous motors parameters and the operation characteristics. This paper has got a novelty character, emphasizes the role of the electromagnetic stresses and the constructive dimensions in the total cost optimization for high power asynchronous motors; it is based on the utilization of the modern numerical methods and the afferent software. There have been performed significant simulations, which bring quantitative and qualitative information necessary for finding the final optimum solution, by considering the customers restrictive conditions regarding the machine gauge. The optimization study has been done by the minimum total cost criterion, by considering twelve variables: A - the current sheet; B - the air gap magnetic induction; J1, J2b, J2i - the current densities into the stator winding, rotor winding and the short-circuit ring; Bj1, Bj2 - the magnetic inductions in the stator and rotor yoke; D - the machine diameter; δ - the air gap; βc1, βc2, βi - the form factors for the stator slot, the rotor slot and the short-circuit ring. The optimization advantages are emphasized by the simultaneous presentation of the three variants of motors: Vm - the existing variant of motor; Vo - the optimum variant; Vd - the unfavourable variant (which has the maximum total cost). The total cost of the optimized motor decreased with 12,2% in comparison to the existing motor (designed by using the known method) and with 27,5% in comparison to the unfavourable variant. Since there are many such motors in use it appears that the saving is significant.

Improvement of pre-determination precision of operation characteristics for asynchronous motor by considering magnetic saturation

The decisive elements establishing the technical and economic success of a constructive solution of an asynchronous motor are the answer characteristics in dynamic regime, the energy consumption, the gauge dimensions, the speed range, the answer time, the noise level, and a final aspect, important in equal extent, is the cost price. All these performances can be performed with the help of the electronic computer on the basis of some adequate programs, leading to an economic fabrication and utilization of the driving electrical equipment fitted out with asynchronous motors.

Modeling of saturation in salient pole synchronous machines

The design of high performance motors must take into account not only the steady state but also practically inevitable dynamic state. In such conditions an accurate predetermination of the parameters and constructive solution by modeling and simulation of the dynamic state, becomes a mandatory step. In this aim, in the present paper an enhanced mathematical model of the synchronous machine is briefly presented. We proposed to consider especially the effects of the magnetic saturation, with preservation of the fundamental harmonic of the magnetic field, and saliency. The model assumptions are specified and it is shown that they ensure and improved representation of the main field saturation and saliency. The enhanced model proves to be useful and versatile and is recommended for the analysis of complex dynamical processes when a high accuracy is required. The qualitative and quantitative results show an important number of valuable information in the design stage of the synchronous machine.

Using GUI of Matlab to create a virtual laboratory to study an induction machine

Recently, appeared the powerful data-processing tools, which allows simulating the dynamic systems in a simple way, in graphic environment. The article briefly presents how to use the software of Graphical User Interfaces (GUI) of MATLAB and shows its application to a traditional problem of dynamics of the electric machines: the simulation of the starting of an asynchronous machine. The goal of this paper is to provide electrical engineers and students with an introduction to the GUI. The same approach can be used to solve more difficult problems.

Modeling and Simulation of Magnetic Saturation in Induction Motors

It is proved that for different combinations of currents and flux linkages as state variables, there is a common theoretical support that simplifies the obtaining of the mathematical models of the saturated induction machine. Three models are compared: the exact one that introduce the cross- inductance Ldq , the classic one and simplified one for the simulation of the speed reversal process. For Ldq ne ct. and random, the exact method appears compulsory.

Aspects Regarding Simulation of the Saturated Induction Motors Control by the Voltage Inverter Commanded in Current

In this paper there is analysed the influence of the induction motors parameters on the transient states duration of the converter-motor assembly when controlling by the stator flux with the implementation of a current controlled inverter. The mathematical model of the saturated induction machine when considering the magnetising current and the stator flux as state variables has been used in this purpose. A Matlab program for the simulation of the analyzed system operation has been carried out with its help. Then the simulations have been confirmed experimentally.

Prediction through simulation of the optimal behavior of the induction machine in complex process

In this paper one uses the theory developed by A.Campeanu (1995) to simulate the operation of induction machine in complex dynamic processes. On this basis one can determine in detail the transient behavior of induction machine and some of the factors which condition the operation. The results are useful in the design stage of induction machine which has to operate in prescribed complex dynamic regimes.

Influence of Cross- Saturation for Modeling and Simulation of the Dynamic Processes in the Induction Motor

In this paper there are obtained mathematical models of the saturated induction machines. It is shown that various sets of state variables have a common theoretical background that simplifies the deduction of the saturated models. The possible combinations of the state variables are grouped in two classes for which are established direct calculus algorithms. (1) The winding currents -flux linkages as state variables. (2) The magnetizing current im -currents (flux linkages) of the windings as state variables. Specific computations are performed and there are written the state equations of the electromagnetic processes for several combinations of the state variables. The major aim of the numerical approach is to compare the computational programs. The simulation results points out that in the presence of saturation the simplified models do not reveal in a correct way the complete evolution of the dynamic electromechanical processes. The dynamic variation of the saturation (Ldqne0) essentially justifies the forced electromechanical oscillations.

Method and device of synchronization for determination of squirrel cage asynchronous motors parameters

This paper presents a method for the squirrel cage asynchronous motors parameters determination, which is the object of a invention proposal. The method involves monitoring a direct-on-line starting and processing, by minimizing an objective function, the data recorded during starting. There are also presented the experimental results obtained, with accent on the synchronization device, which is the object of an invention demand, too.

Aspects regarding design of squirrel cage asynchronous motors for mining excavators

This paper aims at emphasizing the importance of the electromagnetic stresses and constructive dimensions in the starting characteristics optimization in case of high power squirrel cage asynchronous motors used for surface mining excavators. Since the motor drives a high capacity excavator, the inertia moment is high and a significant increase of the starting period results. Several significant simulations are presented in this paper; they bring information which is necessary for determining the final optimum constructive solution, where a very low starting current is considered, so that the motor is able to cope with it, during the starting period. The restrictive gauge conditions imposed by the place where the motor is assembled are also considered when the optimum constructive solution is established. The optimization study has been made by the customers criterion - minimum starting current - by using twelve variables: current loading, air-gap magnetic induction, stator and rotor winding current densities, stator and rotor yoke magnetic induction, machine diameter, air-gap, shape factors for the stator and rotor slots, rotor slot isthmus dimensions. The optimized motor has a starting current Ip=2,85*IN (lower by 12,2% in comparison with the limit value imposed by customer) and the total cost (of fabrication and exploitation) is lower by 3,5 % in comparison with the real existing motor of the excavator.