• KIEE International Transactions on Power Engineering
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• v.5A no.1
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• pp.22-30
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• 2005

The PWM inverter drive may cause an over voltage at the motor terminal, which imposes severe electric stresses on the inter-turn insulation of motor windings. Unlike low-voltage induction motors, high-voltage induction motors have a stator type of form-wound coil for insulation and are insulated to the slot and the coil. So, this paper presents a PWM 3-level inverter, H-Bridge cascaded 7-level inverter and High-voltage induction motor model. It then analyzes the voltage that generates at the input terminal of the high-voltage induction motor fed by each inverter. Also, in order to examine a factor that influences the switching surge voltage, this paper proposes the system equivalent model and performs the case studies using EMTP.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2005.11a
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• pp.399-403
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• 2005

In this paper, we analyze on the effect of RC filter to mitigate transient overvoltage on the high voltage induction motor fed by H-bridge cascaded 7-level inverter. The switching surge voltage becomes the major cause to occur the insulation failure by serious voltage stress in the stator winding of high voltage induction motor. The effect of switching surge appears more serious in high voltage induction motor than low voltage induction motor. Consequently, we demonstrated that the RC filter connected to the motor terminals greatly reduces the transient voltage stress md ringing. The results of simulation show the suppression of transient overvoltage at the motor end of a long cable. using EMTP

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.10
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• pp.82-93
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• 2006

In this paper, filters are designed to reduce transients overvoltage in inverter fed high-voltage large-capacity induction motor drive system. Design issues for a LCR filter at the inverter output terminals to reduce the dv/dt of the inverter output pulse and a RC filter at the induction motor input terminals to match the characteristic impedance between cable and induction motor are examined in detail. These filters are modeled to be suitable to high-voltage large-capacity induction motor. The performance of the filter is evaluated through simulation using EMTP(ElectroMagnetic Transients Program). We presented filters that used high voltage large-capacity induction Motor on the basis of this. Effect of the filter is analyzed for variation of the cable length. Characteristics of filters are analyzed to reduce harmonic in voltage waveform of induction motor input terminal. The switching surge voltage became the major cause to occur the insulation failure by serious voltage stress in the stator winding of induction motor. Filter for to mitigate transients overvoltage presents a required component in drive system of high-voltage large-capacity induction motor. Also, proposed filters are proved through simulation using EMTP.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.296-298
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• 1995

This paper proposes a new filter topology that suppresses the high voltage gradient(dv/dt) in ac motor terminals. The high voltage gradient(dv/dt) causes over voltages on the motor windings, the degradation or motor insulation, and the bearing failure. Moreover surge voltage with high voltage gradient(dv/dt) in the PWM inverter red drive system where long line cables are required causes more serious problem to the motor. Thus, the most advisable method is attaching output filter to the inverter output terminals. The conventional output filters have several problems such as bulky size, difficulty or parameter tuning. The proposed filter can be relatively smaller than the conventional filters. By the proposed filter, the shaping or PWM waveform can considerably suppress high dv/dt in motor feeding cable from the inverter. The effectiveness or the proposed filter is compared with that or the conventional one and is verified by the computer simulation.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2005.05a
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• pp.47-50
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• 2005

In this paper, we investigate a filtering technique to reduce the adverse effect of long motor leads on H-bridge cascaded 7-level inverter fed ac motor drive. The switching surge voltage becomes the major cause to occur the insulation failure by serious voltage stress in the stator winding of high voltage induction motor. However, the effect of switching surge appears un seriousin high voltage induction motor than low voltage induction motor. Consequently, we demonstrated that the filter connected to the motor terminals greatly reduces the transient voltage stress and ringing, moreover we show lowers the dv/dt of the inverter switching pulse. The results of simulation show the suppression of dv/dt and the reduced peak voltage at the motor end of a long cable.

• Proceedings of the KIPE Conference
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• 2019.11a
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• pp.96-97
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• 2019

Pulse Width Modulation (PWM) is a widely adopted technique to drive the motor using the voltage source inverters. Since they generate high frequency Common Mode (CM) Voltage, a high shaft voltage in induction motor is induced which leads to parasitic capacitive currents causing adverse effects such as premature deterioration of ball bearings and high levels of electromagnetic emissions. This paper presents an Active Cancellation Circuit (ACC) which can significantly reduce the CM voltage hence the common mode current in the three phase induction motor drives. In the proposed method the CM voltage is detected by the capacitors and applied to the frame of the motor to cancel the CM voltage hence the CM current. Unlike the conventional methods the proposed method does not insert the transformer in between the inverter and motor, a high power rating three phase transformer is not required and no losses associated with it. In addition the proposed method is applicable to any kind of PWM motor drives regardless of their PWM methods. The effectiveness of the proposed method is proved by the experiments with a three phase induction motor (1.1kW 415V/60Hz) combined with a three phase voltage source inverter modulated by the Space Vector Modulation (SVM).

• Proceedings of the KIEE Conference
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• 2004.11b
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• pp.63-65
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• 2004

The recent advancement in the power electronic technique has increased the use of induction motor fed by inverter using high-frequency switching devices. Also the tendency is toward larger size and higher voltage. Therefore, The IGBT (Insulated-Gate Bipolar Transistor) that is high switching frequency element has been using increase. But, The switching surge voltage was occurred by high switching frequency of inverter has appeared a voltage doubling in the motor input terminal due to mismatching of cable characteristic impedance and motor characteristic impedance. Actually, The Switching surge voltage became the major cause to occur the insulation failure by serious voltage stress in the stator winding of induction motor. The short during rise time of switching surge and cable length is increased, the maximum transient voltage seen at the motor terminals increases. In this paper, Analyzed switching surge transient voltage of power cable pulling is used EMTP(Electromagnetic Transient Program) at the induction motor terminal and in cable.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.9
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• pp.1589-1593
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• 2008

The condition of a high voltage motor was monitored with the motor performance monitor (MPM) at the motor control center. The MPM detected defects in the rotor bar and end ring and input power according to motor and load conditions. The assessment of the condition of a coal pulverizer motor indicated it was clearly in good condition in terms of the rotor bars, over voltage, and motor performance. However, the side bands at frequency, 56.48 Hz indicated existence of rotor end-ring fault. The large torque ripple indicated abnormal operating conditions. After visual inspection, it has been observed that an impeller blade of the circulating water pump was broken off causing the irregular torque pattern.

• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.2107-2109
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• 1999

The insulation diagnostic tests was performed at local thermal power plants high voltage motor. The insulation diagnostic tests include measurements of insulation resistance, polarization index, AC current, $tan{\delta}$, partial discharges. This paper describes Insulation characteristics for high voltage motor which located by inside and outside.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.2B no.3
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• pp.81-89
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• 2002

The sensorless AC motor drive is a popular topic of study due to the cost and reliability of speed and position sensors. Most sensorless algorithms are based on the mathematical modeling of motors including electrical variables such as phase current and voltage. Therefore, the accuracy of such variables largely affects the performance of the sensorless AC motor drive. However, the output voltage of the SVPWM-VSI, which is widely used in sensorless AC motor drives, has considerable errors. In particular, the SVPWM-VSI is error-prone in the low speed range because the constant DC link voltage causes poor resolution in a low output voltage command and the output voltage is distorted due to dead time and voltage drop. This paper investigates a novel high-performance strategy for overcoming these problems in a sensorless ac motor drive. In this paper, a variation of the DC link voltage and a direct compensation for dead time and voltage drop are proposed. The variable DC link voltage leads to an improved resolution of the inverter output voltage, especially in the motor's low speed range. The direct compensation for dead time and voltage drop directly calculates the duration of the switching voltage vector without the modification of the reference voltage and needs no additional circuits. In addition, the proposed strategy reduces a current ripple, which deteriorates the accuracy of a monitored current and causes torque ripple and additional loss. Simulation and experimentation have been performed to verify the proposed strategy.