• Journal of Electrical Engineering and Technology
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• v.4 no.2
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• pp.149-158
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• 2009

It is important to derive reliable parameter values in the measurement-based load model development of electric power systems. However parameter estimation tasks, in practice, often face the parameter identifiability issue; whether or not the model parameters can be estimated with a given input-output data set in reliable manner. This paper introduces concepts and practical definitions of the local identifiability of model parameters. A posteriori local identifiability is defined in the sense of nonlinear least squares. As numerical examples, local identifiability of third-order induction motor (IM) model and a Z-induction motor (Z-IM) model is studied. It is shown that parameter ill-conditioning can significantly affect on reliable parameter estimation task. Numerical studies show that local identifiability can be quite sensitive to input data and a given local solution. Finally, several countermeasures are proposed to overcome ill-conditioning problem in measurement-based load modeling.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.906-908
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• 2000

This paper presents dynamic modeling and simulation of induction motors. Equivalent circuit parameters measured by do test, no-load test and locked-rotor test were used as the input data for computer simulation. Operating characteristics of an induction motor were predicted by Matlab/simulink when changing load torque, opening and reclosing of phase a of the stator and three-phase fault at machine terminals.

• Journal of Advanced Marine Engineering and Technology
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• v.6 no.1
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• pp.25-33
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• 1982

The characteristics of the stator current and torque of a small three- phase squirrel cage induction motor and studied experimentally under the situation of a single-phase operation due to various causes. Through the experiments, the torque-slip and current-slip curve of single-phase circuit as well as three-phase circuit are obtained and the needed constants are determined. The stator current and torque are calculated by the current and torque equations derived by the unbalanced circuit theory. The numerical values obtained from the above methods are compared with the experimental values under the same conditions. The results of the study are summerized as follow; 1) The values computed by the unbalanced circuit theory generally come to approach the values recorded through experiments. 2) Near the rated load, speed drop is less than 1.2 per cent of the speed of three-phase induction motor and torque reduces less than 3 per cent of it of three-phase induction motor when three-phase induction motor is run under a single-phase. On the other hand, the stator current in a single-phase circuit is more than 1.9 times of it in three-phase circuit. 3) The stalling torque in a single-phase circuit is reduced to about 41 per cent of it in three-phase circuit while the corresponding slip is moved toward the synchroneous speed and the corresponding stator current is increased.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.2
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• pp.121-126
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• 2008

This paper analyzes the losses of a Steinmetz connection three-phase induction motor which is supplied by a single-phase source. The T-type equivalent circuit which is taken no-load losses into account is used to determine phase converter capacitive reactances at starting and rated speed by using the condition of the minimum voltage unbalance. The starting and the operating capacitor are replaced at the slip of the same voltage unbalance factor points which are depicted using two capacitive reactances. The operation characteristics are investigated by comparing with those of three-phase balanced operation to find the feasibility of single-phase operation. To analyze the losses of this motor, the output power decrease factor(OPDF), the loss ratio(LR), the no load loss ratio(NLLR), the copper loss ratio(CLR), the stator copper loss ratio(SCLR), and the rotor copper loss ratio(RCLR) are defined and simulated in the whole slip range. The simulated results show that OPDF is maintained almost uniformly, LR is low at low speed and high at high speed, CLR is higher !ban NLLR, but CLR varies concavely and NLLR varies convexly at high speed, SCLR is low at low speed and high at high speed, but SCLR varies convexly at high speed, and RCLR is nearly opposite to SCLR.

• Proceedings of the KIEE Conference
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• 2000.07d
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• pp.2464-2466
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• 2000

When linear PI controller is used in speed control of induction motor, there happen some weaks which is very difficult to find optimal control gain at time of changing speed and load. In this paper, Fuzzy system incorporated with PI controller is proposed in order to that defects. PI gain is calculated by theoretical basis and fuzzy control is translated human expert's knowledge and experiences into rules numerically. Also it modifies and compensates PI gains in realtime. As comparing the motor characteristics of proposed fuzzy-PI speed controller to PI speed controller of a Vector controlled induction motor system in the increasing load torque and speed change during start and stop, The simulation results show robust and good performance.

• Proceedings of the KIEE Conference
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• 1999.07b
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• pp.516-518
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• 1999

This paper presents an feed-forward neural network design instead PI controller for the speed control of an Induction Motor. The design employs the training strategy with Neural Network Controller(NNC) and Neural Network Emulator(NNE). Emulator identifies the motor by simulating the input and output map. In order to update the weights of the Controller. Emulator supplies the error path to the output stage of the controller using backpropagation algorithm. and then Controller produces an adequate output to the system due to neural networks learning capability. Therefore it becomes adjustable to the system with changing characteristics caused by a load. The speed control based on neural networks for induction motor is implemented by a vector controlled induction motor. The simulation results demonstrate that actual motor speed with neural network system well follows the reference speed minimizing the error and is available to implement on the vector control theory.

• Proceedings of the KIEE Conference
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• 2008.10b
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• pp.77-78
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• 2008

This paper presents to control speed of induction motors with uncertainties. We use an adaptive backstepping controller with fuzzy neural networks(FNNs) and model reference adaptive system(MRAS) at Indirect vector control method. The adaptive backstepping controller using FNNs can control speed of induction motors even we have a minimum of information. And this controller can be used to approximate most of uncertainties which are derived from unknown motor parameters, load torque such as disturbances. MRAS estimates to rotor resistance and also can find optimal flux to minimize power losses of Induction motor. Indirect vector PI current controller is used to keep rotor flux constant without measuring or estimating the rotor flux. Simulation and experiment results are verified the effectiveness of this proposed approach.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.05a
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• pp.497-504
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• 2000

This paper presents a method for the equivalent-circuit parameters and torque characteristics calculation of squirrel-cage induction motors. The measurment of motor parameters were calculated by the stator resistance test, the blocked rotor test and no load test through T type equivalent-circuit method. Especially, this paper describes the test results obtained by using hall sensor and strain gage for the current and the torque characteristics of induction motors. 1(HP), three-phase squirrel cage induction motor has been used during the test and the parameters are compared with those obtained by the maker parameters of simulation results and experiment.

• Proceedings of the KIEE Conference
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• 1993.11a
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• pp.66-69
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• 1993

Now a days, the inverter fed induction motors are being widely used. In this case, many harmonic voltages cause a additional effect on the characteristics of induction motor. Several characteristics calculation methods have been introduced. But it needs tedious experiments for designer to apply these methods to induction motor because these methods need measurement and test results. This paper presents characteristics calculation method which don't need measurement and test results. And this paper shows that the simulation results agree well with values obtained by actual load test.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.1111-1113
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• 2000

This paper presents the calculation method for the equivalent-circuit parameters and torque characteristics of squirrel-cage induction motors. The measurement of motor parameters were calculated by the stator resistance test, the blocked rotor test and no load test to T type equivalent-circuit. Especially, this paper describes the test results obtained by using hall sensor and strain gauge for the current and torque characteristics of induction motors. Three-phase squirrel-cage induction motor which has 1[hp] was used to the test and the parameters obtained by the test were compared with the maker parameters.