For conventional motor soft starter, the starting torque would be seriously decreased when reduce the starting voltage, so it is limited to light load, However, many overloading start-up is required in practical appli...
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ISBN:
(纸本)9781424435197
For conventional motor soft starter, the starting torque would be seriously decreased when reduce the starting voltage, so it is limited to light load, However, many overloading start-up is required in practical applications. According to the relationship between three-phase asynchronous motor electromagnetic torque and power frequency, when keeping the size of voltage unchanged, the torque can be increased by reducing the power frequency. Keeping the main circuit of original motor soft starting system unchanged, the motor rotation is controlled by changing the thyristor trigger angle, converting the frequency which add up in the stator and utilizing the fundamental components. This paper presents a method of improving starting torque based on discrete variable frequency and the three-phase asynchronous motor soft starter model is established using MATLAB. The simulation results illustrate discrete variable frequency softer starter has many advantages in current, speed and torque compared to full-voltage starter and current limit starter.
This paper analysis the control principle of the asynchronous motor soft-start with discrete variable frequency technology. A simulation model for the asynchronous motor soft-starter using discrete variable frequency ...
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ISBN:
(纸本)9783037855744
This paper analysis the control principle of the asynchronous motor soft-start with discrete variable frequency technology. A simulation model for the asynchronous motor soft-starter using discrete variable frequency technology is built based on MATLAB SEMUUNK/POWER SYSTEM. In start process, positive sequence sub - frequency such as 13, 10, 7, 4 discrete variable frequency is used in the soft-starter to simplified power circuit and its control. While on the power frequency time slice,a single neuron PID algorithm is used to limit the current. The simulation results verify the asynchronous motor soft-starter with discrete variable frequency technology not only reduces the initial firing current but also has bigger start torque, which has a faster start speed compared with the normal soft starter with current limit starting control technology.
The started motors with the discretefrequency converter are characterized by high staring torque and a large number of harmonics when the motors draw heavy-loads. It may pull down the voltage of the power supply netw...
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ISBN:
(纸本)9783037858967
The started motors with the discretefrequency converter are characterized by high staring torque and a large number of harmonics when the motors draw heavy-loads. It may pull down the voltage of the power supply network;it will severely influence the other electrical devices in the same power network. Furthermore, it increases the motor temperature, which may lead to motor damage. Therefore, a novel integrated method of motor discrete variable frequency starting and harmonic filtering is presented in this paper, to achieve quick and smooth motor starting, to produce high staring torque, to keep the harmonics in permitted ranges. The following works have been done in the study: analyze the principle, design the structure of the integrated device, and present the implementation steps. The motor starter developed with this method has been successfully applied to the loads of the drive equipments in the kiln, coal grinding mill or the mine. It can improve the starting performance when the motors draw the heavy-loads, save energy, stabilize the voltage of the power supply network.
To further research the response of the tearing mode（TM） to dynamic resonant magnetic perturbation（DRMP） on the J-TEXT tokamak, a modified series resonant inverter power supply（MSRIPS） with a function of discret...
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To further research the response of the tearing mode（TM） to dynamic resonant magnetic perturbation（DRMP） on the J-TEXT tokamak, a modified series resonant inverter power supply（MSRIPS） with a function of discrete variable frequency is designed for DRMP coils in this study. The MSRIPS is an AC–DC–AC converter, including a phase-controlled rectifier, an LC filter, an insulated gate bipolar transistor（IGBT） full bridge, a matching transformer, three resonant capacitors with different capacitance values, and three corresponding silicon controlled rectifier（SCR） switches. The function of discrete variable frequency is realized by switching over different resonant capacitors with corresponding SCR switches while matching the corresponding driving frequency of the IGBT full bridge. A detailed switching strategy of the SCR switch is put forward to obtain sinusoidal current waveform and realize current waveform smooth transition during frequency conversion. In addition, a resistor and thyristor bleeder is designed to protect the SCR switch from overvoltage. Manufacturing of the MSRIPS is completed, and the MSRIPS equipment can output current with an amplitude of 1.5 kA when its working frequency jumps among different frequencies. Moreover, the current waveform is sinusoidal and can smoothly transition during frequency conversion. Furthermore, the transition time when the current amplitude rises from zero to a steady state is less than 2 ms during frequency conversion. By using the MSRIPS, the expected discrete variable frequency DRMP is generated, and the phenomenon of the TM being locked to the discrete variable frequency DRMP is observed on the J-TEXT tokamak.
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