Over Voltage Analysis of Rotor in 100 MW Generator
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The over voltage of rotor happened in a 100MW water-cooled generator.And it is different obviously with another same type generator.In this paper,the trend of over voltage is analyzed and the hidden trouble is found.The temperature trend of cooling water in different generator is different.Finally,the treat method is put forward.Keywords:
Electric generator
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This study analyses the voltage dip behaviour of the doubly‐fed induction generator (DFIG) connected to a common dc link on both the stator and rotor sides, via a diode bridge and a voltage source inverter (VSI), respectively. After a voltage dip in the dc grid, the rotor VSI can transiently lose control so that rotor currents circulate through the VSI free‐wheeling diodes. However, during the uncontrolled period, both stator and rotor voltages are clamped to the same dc‐link voltage and no rotor overvoltage occurs. In order to analyse the behaviour of the system during the first periods of the uncontrolled current transients, this study presents a simplified average model which is validated through simulations. Voltage dips are classified into three types depending on their severity. A simple analytical expression is derived for the maximum amplitude of the current during the voltage dip, and an overcurrent chart in the plane ‘rotor speed – dip amplitude’ is deduced. These results provide deep insight into the DFIG‐DC system behaviour and are useful for design purpose.
Overcurrent
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This paper present an investigation on over voltage occurring at motor terminals when motor is supplied with a PWM converter. When motor is operated on sinusoidal supply, then, during switching period voltage across motor phase becomes equal to supply line voltage and the maximum voltage across any of the coil obtained is 30% more than the rated value; however this is not producing large over voltages or high rate of rise of voltage. Voltage rise time when motor is supplied with PWM converter is very small and is of the order of micro second. In some cases the peak voltage at motor terminals reaches to a value which more than twice the value of dc link voltage and rated line to line voltage of the motor. The distribution of voltage during switching condition is not equal among the coils of a winding and hence turns. The voltage drop in coils near terminal is more than that of in other coils. The measured voltage drop across first coil from terminal of winding of four coils in series is varying 30 to 56% of the phase voltage against 25% of the phase voltage. During the transition period voltage across first coil may be 70% of the total voltage. This paper highlights the factors which affects the magnitude of over voltage and its propagation in motor winding.
Universal motor
Voltage drop
Disturbance voltage
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A of circuit and characteristic in high voltage power are discussed,and their merit and disadvantage are analyzed,and complex instance and reason in the work are put forward.
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Preliminary studies of voltage vs. speed relationships, stability of generated voltage, and voltage compensation of the self-excited induction generator are presented. In order to improve the voltage regulation, the long-shunt connection of the capacitors to the generator is used. The magnetizing inductance of the machine is used as a saturable reactor. The values of the capacitors for series and parallel connections are obtained from the saturation characteristics of the machine. Experimental results are reported. The maximum voltage drop is about 4%. >
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This paper describes an experimental setup of a voltage sag generator (VSG) based on impedance switching. Bidirectional switches with IGBTs, snubber and clamping circuits are adopted to obtain fast turn on, turn-off while avoiding undesirable voltages and currents stresses. In addition, with the proposed VSG it is possible to adjust the depth and duration of balanced and unbalanced voltage dips making it possible to observe the behavior of wind turbines (WT) under, for instance, voltage dips indicated in the IEC 61400-21.
Snubber
Voltage Sag
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본 논문에서는 변압기 기반 전압변동 발생기의 직렬변압기에 의한 전압강하 특성을 분석하였다. 전압변동 발생기의 회로구성 방식에는 여러 가지가 있으나 본 논문에서는 비교적 비용이 저렴하고 신뢰도가 높은 직렬변압기를 사용한 방식에 대해 다루고자 한다. 직렬변압기에 의한 전압강하는 변압기의 %Z와 부하용량 및 부하역률에 의해 결정된다. 직렬변압기의 설계가 잘못되면 전압강하가 심각하게 발생하여 제대로 된 성능을 확보할 수 없다. 본 논문에서는 10kVA급 전압변동 발생기에 대해 %Z가 4%인 직렬변압기를 사용한 경우 부하역률에 따른 전압강하를 분석하였으며 지상 부하일수록 전압강하가 증가하고 역률이 0.85 지상인 경우 전압강하가 4% 발생함을 시뮬레이션 및 실험을 통하여 확인하였다. A voltage drop characteristics of a transformer-based voltage disturbance generator with series transformers is analysed. It is well known that a voltage disturbance generator with series transformer is cost-effective and reliable compared with other types. The voltage drop depends on the %Z of the transformer, power rating, and output power factor. A wrong design of the transformer results in a severe voltage drop, which can not guarantee the proper performance of the generator. The voltage drop is analysed under the condition of 10kVA output power rating and 4% of %Z with the variation of power factor. It is found through simulations and experiments that the drop increases as the power factor decreases in lagging mode, and the drop is 4% of the rated voltage in case of 0.85 lagging power factor.
Voltage drop
Lagging
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Based on a simplified generator model,the eigenvalue analysis is performed on a single machine-constant power load system to study effects of the high voltage side voltage control(HSVC) on system voltage stabilities.It is shown that the HSVC can improve power system voltage stabilities.Theoretical analysis and time-domain simulation proves the results.
Mesh analysis
High Voltage
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Voltage sags are typically caused by fault conditions. The voltage sag condition lasts until the fault is cleared by a protective device. This paper describes the causes of voltage sags on the generators. It is observed that the armature current, voltage, torque, rotor angle, excitation current of the synchronous generator are also considerably affected by voltage sags. It is shown that shunt capacitors have an effect on the generator terminal voltage and the torque. It can be shown for a simple system that shunt capacitors affect the voltage sag and behavior of the synchronous generator. It is also observed that the electromagnetic torque of the generator is considerably affected by the voltage sag. The existence of shunt capacitors reduce the effect of voltage sag on both the terminal voltage and the torque of the machine.
Voltage Sag
Overvoltage
Shunt generator
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This paper expounds the malfunction seeking and analysis of inter-turn short-circuit of rotor windings in generator No.2 in A plant,points out that the inter-turn short-circuit can be diagnosed by measuring AC impedance power loss,AC voltage distribution of the rotor windings and generator shout-circuit curve,and its harm is emphasized.
Short circuit ratio
Turn (biochemistry)
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Motor over voltage failure of 2250 hot strip mill production line in a company is analyzed.When PWM converter is connected to a motor with long cable,over voltage will be produced on motor side,because of distributing capacitance and inductance.Over voltage mechanism of voltage source PWM converter was studied,and relation between voltage pulse rising time and cable length was analyzed.Reactor was adopted to suppress over voltage,and parameter selection and design method were proposed.It has been applied to production line,and good effect was obtained.
Line (geometry)
Production line
High Voltage
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