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Variable-frequency drive

About: Variable-frequency drive is a research topic. Over the lifetime, 837 publications have been published within this topic receiving 5691 citations. The topic is also known as: VFD.


Papers
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01 Jan 1997
TL;DR: In this article, three methods for the detection of rotor damage in an induction motor controlled by a variable frequency drive are described: synchronous sampling of the stator current waveform using phase locked loop circuitry, time-frequency and wavelet analysis, and frequency spectrum analysis of the instantaneous input power of the motor.
Abstract: This paper describes three methods for the detection of rotor damage in an induction motor controlled by a variable frequency drive. They are (i) synchronous sampling of the stator current waveform using phase locked loop circuitry, (ii) time-frequency and wavelet analysis of stator current, and (iii) frequency spectrum analysis of the instantaneous input power of the motor. Experimental results from the three methods are presented. Some conclusions are drawn for the application to condition monitoring.

1 citations

Proceedings ArticleDOI
24 Oct 2011
TL;DR: In this article, the authors mainly focus on speed synchronization and power balance control in multi-motor belt conveyer system when the variable frequency drive of the motors working in the constant voltage and frequency ratio mode.
Abstract: This paper mainly focus on speed synchronization and power balance control in multi-motor belt conveyer system when the variable frequency drive of the motors working in the constant voltage and frequency ratio mode. And the synchronization compensation control proposal based on current feedback is proposed. In order to get the exact result in simulation, the load torque model versus speed is established, the simulation results prove that this proposal is feasible. The experiment system is in master-slave mode, the experiment data and wave forms prove this proposal can be used in industrial application.

1 citations

Proceedings ArticleDOI
Zhijun Fu1, Qian Wang1, Lei Wang1, Jingjing Xu1, Yiwang Qiu1, Chaofeng Li1 
19 Oct 2020
TL;DR: For those low production wells, relatively low and constant-changing pumping speed not only largely decrease producing energy needs, but also reduce rod-on-tubing wear, so the test wells have improved system efficiency and prolonged mean time between failures (MTBF).
Abstract: Improving pumping system efficiency in low production wells has been a big challenge for most of mature fields in China. These wells often cause high energy consumption and additional mechanical wear because of relatively high pumping speed and nonoptimalpower input for motor drive, even though operators respond it by simply turning down the stroke per minute (SPM) or adopting variable intermittent production scheme based on the well conditions. Therefore, for low production wells, it is important to produce more oil with lower energy input or operational cost. In recent years, researchers proposed a few high-efficiency intelligent control strategies used for these wells, but rarely could be effective and widely used in the field due to the lack of behavior improvement and adaptability. Based on the results from previous research, this paper provides a new solution on flexible variable frequency drive to address the aforementioned challenges. To obtain high system efficiency for low production well, firstly new solution, under a preset and fixed SPM, manage to change pumping speed within each cycle. This can be done utilizing the pumping net load data which is calculated by controller algorithm. Then, it will regulate the SPM based on the real time production data (mainly for fluid rate) which is automatically collected by a specialized wellhead flow meter. Since flow rate is the most effective and direct data to demonstrate reservoir capacity, it can guarantee an accurate and reasonable pump SPM. All adjustments above would be done through continuously regulating the motor electrical parameters, such as voltage and current, using converter and control algorithm built in the flexible controller. Real-time matching to the lifting load and well capacity can realize the best motor drive pattern and avoid the waste of energy. Tow set of process control makes up the new control strategy and fulfills a more ideal pumping operation. For different well capacity, new technology allows the pump frequency to be regulated from 0.5 SPM to 12 SPM under a stable running condition. Each stroke has an adjustable rate process to match inconstant net load. For those low production wells, relatively low and constant-changing pumping speed not only largely decrease producing energy needs, but also reduce rod-on-tubing wear. Thus, the test wells have improved system efficiency and prolonged mean time between failures (MTBF). This paper would describe the control principle of flexible variable frequency drive system in detail and demonstrate its application through two well cases.

1 citations

Patent
22 Dec 2015
TL;DR: In this article, a variable frequency drive (VFD) drives the motor and communicates with the control circuitry of the brake controller, and the amount of stored back EMF corresponds to the time to empty a pump.
Abstract: The invention relates to fluid drive systems used in fluid wells and brake systems for permanent magnet wellhead direct drives. The braking controller connects or disconnects a brake resistor from a back EMF. A variable frequency drive (VFD) drives the motor and communicates with the control circuitry of the brake controller. The control circuitry monitors the brake resistor and depending on the rotational speed and direction of the motor and operating state of the VFD, disconnects or connects the brake resistor. If the direction of the motor is in reverse and above a threshold speed, it connects the brake resistor. If the direction of the motor is in reverse and below the threshold speed, the control circuitry dissipates stored back EMF through the brake controller. The amount of stored back EMF corresponds to the time to empty a pump.

1 citations

Proceedings ArticleDOI
01 May 2017
TL;DR: The aim of this study was to define a relation between voltage unbalance and variable frequency drive power and the mathematical models of drives with a cycloconverter and a frequency converter with a DC link were elaborated.
Abstract: Variable frequency drives are widely used in industrial enterprises and are therefore an influential part of electric load. The aim of this study was to define a relation between voltage unbalance and variable frequency drive power. The mathematical models of drives with a cycloconverter and the frequency converter with a DC link (independent current and voltage inverter) were elaborated. Mathematical models enable computations of unbalanced modes of power grid with response to electric load impact. This solution increases computation accuracy.

1 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20239
202220
202143
202084
201956
201887