• The Journal of Korean Institute of Communications and Information Sciences
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• v.15 no.5
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• pp.384-398
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• 1990

This paper compares and shows the characteristics of various PWM strategies used to generate pulse signals of voltage source inverter. We designed the inverter using PTR and constituted the variable speed drive (VSD) system. For each PWM strategy, acoustic noise level, line-to-line voltage and current waveform, and current harmonic spectrum are measured with respect to the VSD of induction motor. The Suboptimal PWM strategy showed the similar harmonic effects to those of the Optimal PWM strategy. In addition, the microprocessor application was available to the former. The TP PWM strategy was excellent in that it could reduce the CPU load and increase the output voltage since the strategy could control only two phase of the three.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.12 no.4
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• pp.386-398
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• 1987

This paper is proposed the Suboptimal PAWM(Pulse Amplitude Width Modulation) for minimize harmonic effects generated by switching operation of PWM Inverter. This strategy determine one switching pattern at a fixed point(fundamental) voltage u1=1.2) which THD(Total Harmonic Distortion) are minimized in the suboptimal PWM strategy, and controls only frequency in the inverter while voltage control is carried out by DC Chopper in the DC Link. This strategy is applied at VSD(Variable Speed Drive) of Three phase induction moter, and acoustic noise of motor, line to line voltage and current of inverter, current harmonic spectrum was estimated and also compared with other switching strategy. From the results, the validity of this strategy can be verified.

• Journal of Power Electronics
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• v.17 no.5
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• pp.1244-1255
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• 2017

The space vector pulse width modulation (SVPWM) technique is a popular PWM method for medium voltage drive applications. Conventional SVPWM (CSVPWM) and bus clamped SVPWM (BCSVPWM) are the most common SVPWM techniques. This paper evaluates the performance of various advanced BCSVPWM strategies in terms of their harmonic distortion and switching loss based on a uniform frame work. A uniform frame work, pulse number captures the performance parameter variations of different SVPWM strategies for various number of samples with heterogeneous pulse numbers. This work compares different advanced BCSVPWM techniques based on the modulation index and location of the clamping position (zero vector changing angle ) of a phase in a line cycle. The frame work provides a fixed fundamental frequency of 50Hz. The different BCSVPWM switching strategies are implemented and compared experimentally on a 415V, 2.2kW, 50Hz, 3-phase induction motor drive which is fed from an IGBT based 2 KVA voltage source inverter (VSI) with a DC bus voltage of 400 V. A low cost PIC microcontroller (PIC18F452) is used as the controller platform.

• Journal of KSNVE
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• v.13 no.2
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• pp.109-118
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• 2003

With the rising utilisation of electrical machines to increase the output-Power of the device several problems occur. Next to probable additional losses and other parasitic effects, aspects concerning the audible noise radiated by the device are of particular interest. This contribution is intended to give an overview to the problematic of the analysis of vibrations and audible noise radiated by electrical machines. It is not the intention of the authors to set off a scientific firework with various complicated equations in this contribution. The paper should rather give an insight in a complicated technical matter and should help to understand the mechanism of vibration and parasitic noise generation in electrical machines. Rotating machines, such as the induction motor as well as non-rotating electrical machines, such as inductors or transformers are studied. The origin of vibrations leading to noise radiations is studied and discussed to illustrate the way in which the analysis of the governing effects can be performed. Magnetically generated radial pullout force waves in rotating electrical machines are the main cause of the excited audible noise, whereas magnetostriction plays an important role in transformers.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.1 s.106
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• pp.27-33
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• 2006

Fault diagnosis and condition monitoring for rotating machines are important for efficiency and accident prevention. The process of fault diagnosis is to extract the feature of signals and to classify each state. Conventionally, fault diagnosis has been developed by combining signal processing techniques for spectral analysis and pattern recognition, however these methods are not able to diagnose correctly for certain rotating machines and some faulty phenomena. In this paper, we add a minimum detection error algorithm to the previous method to reduce detection error rate. Vibration signals of the induction motor are measured and divided into subband signals. Each subband signal is processed to obtain the RMS, standard deviation and the statistic data for constructing the feature extraction vectors. We make a study of the fault diagnosis system that the feature extraction vectors are applied to K-means clustering algorithm and minimum detection error algorithm.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.14 no.5
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• pp.66-73
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• 2000

A new modified command voltage of the third harmonics injected PWM inverter is proposed to control the inverter in overmodulation mode. The third harmonics injected PWM has a extended linear region compared with the sine PWM. But it still has a maximum voltage about 90% compared with the six step inverter. By analyzing the relationship between the modulation index and the peak of the fundamental component of the modified reference voltage, we can settle the problem in over modulation mode without iteration. Then we can increase the maximum fundamental component of the third harmonics injected PWM inverter comparative to six-step inverter continuously in over modulation mode. The simulation results of the inverter-induction motor system shows the validity of this method.

• Journal of Korea Foundry Society
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• v.26 no.1
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• pp.40-45
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• 2006

Most of the work reported concerned the semi-solid processing of low melting point alloys, and in particular light alloys of aluminum and magnesium. The purpose of this paper is to develop a semi-solid microstructure of Cu alloys using electromagnetic stirring applicable for squirrel cage rotor of induction motor. The size of primary solid particle and the degree of sphericity as a function of the variation in cooling rate, stirring speed, and holding time were observed. By applying electromagnetic stirring, primary solid particles became finer and rounder relative to as-cast sample. As the input frequency increased from 30 to 40 Hz, particle size decreased. The size of primary solid particle was found to be decreased with increasing cooling rate. Also, it decreased with stirring up to 3 minutes but increased above that point. The degree of sphericity became closer to be 1 with hold time. Semi-solid microstructure of Cu alloys, one of the high melting point alloys, could be controlled by electromagnetic stirring.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.285-287
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• 2001

To obtain a high performance in a vector controlled induction machine, it is essential to know the instantaneous position of the rotor flux which depends on the rotor time constant. But the rotor time constant mainly varies due to the temperature rise in the motor winding, so real time compensating algorithm is necessary. This paper proposes that it uses short duration pulses added to the constant flux command current and then resultant torque command current produced by speed controller is utilized for the rotor resistance estimation. This method has advantages with a low computational requirement and does not require voltage sensors. The proposed method is proved by simulations.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.803-804
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• 2006

우리는 이전 논문을 통해 Air blower용 모터에서 널리 사용되고 있는 단상 유도기를 기존의 분포 권선 방식에서 벗어나 집중 권선 방식을 사용하여 설계한 결과 생산 공정의 단계를 줄이고 많은 생산 비용을 줄일 수 있었다. 또한 집중 권선형에서 발생할 수 있는 고조파 문제를 로터의 skew와 overlap 권선 방식을 이용하여 해결 할 수 있음을 증명하였다. 그러나 이러한 이점에도 불구하고 시제품의 특성을 측정한 결과 집중 권선형 모터의 자계 불균형 때문에 기존 분포권 모터에 비해 소음과 진동 특성이 좋지 않은 결과를 보였다. 이에 본 논문에서는 소음과 진동 특성을 고려하여 기존의 기동 및 정격 토크 특성을 유지하면서 토크 리플을 저감할 수 있는 방법을 로터의 Skew 각도 영향, 권선 사양 및 스테이터 및 로터 형상 등을 고려하여 새롭게 설계하였고 그 결과를 제시하였다.

• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.147-149
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• 1994

In designing high efficiency electrical machines, calculation of iron loss is very important. And it is reported that in the induction motor and in the T-joint of 3 phase transformer, there occurred rotational magnetic field and much iron loss is generated owing to this field. In this paper, rotational power loss in the electrical machine under rotational magnetic field is discussed. Until now, loss analysis is based on the magnetic properties under alternating field. And with this one dimensional magnetic propertis, it is difficult to express iron loss under rotational field. In this paper, we used two dimensional magnetic property data for the numerical calculation of rotational power loss. We used finite element method for calculation and the analysis model is two dimensional magnetic property measurement system. We used permeability tensor instead of scalar permeability to present two dimensional magnetic properties. And in this case, we cannot uniquely define energy functional because of the asymmetry of the permeability tensor, so Galerkin method is used for finite element analysis.