Krzysztof Makowski and Aleksander Leicht
The purpose of this paper is to present analysis of short-circuit transients in a single-phase self-excited induction generator (SP-SEIG) for different capacitor topologies.
Abstract
Purpose
The purpose of this paper is to present analysis of short-circuit transients in a single-phase self-excited induction generator (SP-SEIG) for different capacitor topologies.
Design/methodology/approach
The paper presents field analysis of the short-circuit problem in the SP-SEIG on the base of two-dimensional field-circuit model of the generator.
Findings
The carried-out field computations of the tested SP-SEIG show that the self-excited induction generator is intrinsically protected from the results of sudden short-circuit, as output voltage and current drop rapidly to zero. Short-circuit is a problem when a series capacitor is used to improve output voltage regulation. Experimental results show that re-excitation of the generator is possible after the short-circuit is removed.
Originality/value
The originality of the paper is the presented analysis of short-circuit transients at terminals of SP-SEIG. A finite elements method-based field circuit model was used. The simulation results were validated by the measurements conducted on a laboratory test setup.
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Aleksander Leicht and Krzysztof Makowski
The purpose of the paper is to present an analysis of an influence of shape and material of rotor bars on the process of self-excitation and performance characteristics of…
Abstract
Purpose
The purpose of the paper is to present an analysis of an influence of shape and material of rotor bars on the process of self-excitation and performance characteristics of single-phase, self-excited induction generator (SP-SEIG).
Design/methodology/approach
The presented analysis is based on the results of transient simulations of SP-SEIG performed with the use of field-circuit model of the machine. Four various shapes of the rotor bars and two different conductor materials were investigated. The results for the base model with rounded trapezoidal rotor slots were validated by measurements.
Findings
An improvement of the performance characteristics – the extension of the stable operating range of the generator – was obtained for rectangular copper rotor bars. The improvement is the result of strong skin effect in the squirrel rotor cage. Application of round rotor slots results in shorter time of voltage build-up during the self-excitation of the generator caused by less apparent deep bar effect in round bars.
Originality/value
The originality of the paper is the application of the copper rotor cage in the single-phase, self-excited induction generator. Its use is beneficial, as it allows for extension of the range of stable operating range. The results may be used for designing new constructions of the single-phase, self-excited induction generators, as well as the constructions based on general purpose single-phase induction motors.
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Krzysztof Makowski and Marcin J. Wilk
The purpose of this paper is to present optimization of a single-phase capacitor induction motor with respect to efficiency and starting torque by using surrogate field-circuit…
Abstract
Purpose
The purpose of this paper is to present optimization of a single-phase capacitor induction motor with respect to efficiency and starting torque by using surrogate field-circuit model for steady-state. As variables, dimensions of the rotor slots and capacitor capacitance were assumed, whereas outputs were the motor performance characteristics. Searching for a motor design of maximum starting torque or maximum efficiency were objectives of the optimization. To verify design solutions, rated load and locked rotor tests of the optimized motors were performed by computer simulation which confirmed better performance parameters of the optimized motors.
Design/methodology/approach
The paper presents optimization procedure of a single-phase capacitor induction motor by applying response surface methodology for surrogate 2D field-circuit model of the motor. For solving the problem a single-objective and bi-objective approach were applied.
Findings
The carried out calculations showed that obtained new structures of the capacitor induction motor have better starting properties – the higher ratio of starting to rated torque. It was also obtained the motor construction with higher efficiency and lower stator current at the same time.
Originality/value
The main advantage of the formulated optimization procedure was application of the SSO (sequential surrogate optimization) algorithm which exploits a polynomial surrogate model and genetic algorithm to find minimum of the objective functions and also to speed up computations.
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Krzysztof Makowski and Aleksander Leicht
The purpose of this paper is to present analysis of an influence of rotor slots opening on self-excitation process, terminal voltage and performance characteristics of the…
Abstract
Purpose
The purpose of this paper is to present analysis of an influence of rotor slots opening on self-excitation process, terminal voltage and performance characteristics of the single-phase self-excited induction generator (SPSEIG).
Design/methodology/approach
The paper presents field analysis of the self-excitation problem in the SPSEIG and performance characteristics on the base of two-dimensional field-circuit model of the generator.
Findings
The carried out field computations of the tested SPSEIG with closed rotor slots showed that only an initial voltage across the excitation capacitor of about nominal value (230 V) causes successful self-excitation of the generator. It was also proved that the suitable opening of the rotor slots, beside remnant flux density in the rotor core, facilitates self-excitation in the generator. Since in working applications initially charging of the capacitor to almost nominal voltage may cause a problem, therefore employment of semi-closed rotor slots in the SPSEIG would be proper solution.
Originality/value
The conducted simulations, validated by laboratory tests showed that not only suitable excitation capacitor capacitance and rotor speed are needed to obtain desired terminal voltage of the generator, but also suitable initial voltage across the capacitor in auxiliary stator winding is very important and necessary for reliable self-excitation of the single-phase induction generator with closed rotor slots. The employment of semi-closed rotor slots in the SPSEIG makes the self-excitation more effective.