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.

VFD Control for Industrial Machines using PLC and LC Filter

Abstract: Variable frequency drive (VFD) and servo drive usage in the industrial application are increased in a large amount. The control of VFD can be done using a programmable logic controller (PLC). The apparatus includes a main controller i.e. VFD and first interface PLC. The motor controller (VFD) is coupled to the PLC and controls the electric motor according to the application. PLC is further coupled to Human Machine Interface (HMI) to show the operation visually. An input to VFD is given from the PLC to run the motor and outputs from the VFD is controlled frequencies, which control the speed and torque of a motor. Harmonics, motor bearing damage, motor noise, electromagnetic interference are observed in the pulse width modulated (PWM) VFD fed induction motor. A sinusoidal LC filter is placed between the VFD and motor to smoothen the pulse width modulated waves into sinusoidal waves, which basically reduces the noise and effectively improve the overall efficiency of VFD.

Repairing and commissioning of an AC motor speed controller for a centrifugal pump

Abstract: A centrifugal pump was installed in 1984 in the Fluid Mechanics Laboratory of Mechanical Engineering Department of Rajshahi University of Engineering & Technology. The motor of the centrifugal pump was dc motor and was not working. It could not be commissioned for a long time because of the damaged speed controller. The main shaft (rotor) was also jammed. In this project work, the dc motor was tried to repair. But it could not be run because the specification of the motor and the operating manual was not available. To complete the project successfully, the dc motor was replaced by an ac induction motor. After replacing the motor, the speed of the new motor was controlled by a variable frequency drive (VFD). Using this device, the speed was controlled from 600 rpm to 3000 rpm smoothly. After the replacement, the testing of the centrifugal pump was successfully performed and the motor was controlled in various speeds. Experiment on the performance test of the centrifugal pump was carried out satisfactorily running the pump in various speeds operated by the VFD.

Control system applied to variable frequency drive type scraper conveyor

Abstract: The utility model relates to a control system applied to a variable frequency drive type scraper conveyor, in particular to a scraper conveyor control system for performing variable frequency control through a position signal of a coal mining machine and a real-time coal transportation volume signal of the scraper conveyor. The control system acquires a running frequency signal of an explosion protection frequency converter by computing with a designed programmed algorithm according to signals provided by weighing sensors, a recognition sensor and a lower computer signal acquisition controller, and a controller of the explosion protection frequency converter controls running of an explosion protection motor according to the signals. The problem that the variable frequency drive type scraper conveyor cannot be adjusted in transport capacity in real time according to load characteristics is solved, the scraper conveyor is allowed to be adjusted in transport capacity according to comprehensive running conditions of working faces, and the variable frequency drive type scraper conveyor is enabled to form a closed-loop variable-frequency speed regulating running system. Automation level of the fully mechanized coal face can be heightened, and electric energy consumed for mining can be saved.

Start control method and device for permanent magnet synchronous motor

Abstract: The invention provides a start control method and device for a permanent magnet synchronous motor, and relates to the technical field of variable frequency drive. According to the method and the device, quadrature axis current remains the same when the quadrature axis current is equal to a preset quadrature axis current set value; the rotation speed of the quadrature axis current remains the samewhen the rotation speed of the quadrature axis current is equal to a preset rotation speed given value; when the time for maintaining the constant state of the quadrature axis current is greater thana preset time, the quadrature axis current of the permanent magnet synchronous motor is given according to a preset second current change slope; and when a torque angle is equal to a preset angle, a closed-loop running state is cut in; the quadrature axis current remains unchanged when the quadrature axis current is equal to the preset quadrature axis current set value, and the quadrature axis current is given again after a certain period of time; sudden changes in the current and the like are avoided; the start process of the permanent magnet synchronous motor is highly reliable, and at the same time the rotation speed is stable; and the operation is stable.

The Electromagnetic Torque Ripple of Three-Phase Induction Electric Machine, Operating as a Part of the Auxiliary Electric Drive Onboard of AC Electric Locomotive - a Factor Contributing to the Failure of Bearings

Abstract: The paper deals with the results of computer simulation of electromagnetic torque of auxiliary induction motors and phase splitters type NVA-55 (4-pole, 55 kW) onboard of AC electric locomotive “Ermak”, which made in Russia. Because of the unbalanced system of electrical voltages (sinusoidal taken as a first approximation), except a constant electromagnetic torque component comprises in all cases the significant harmonic component of 100 Hz frequency, and in cases of squirrel cage broken bars presence - in the time harmonics spectrum frequencies from 10 Hz to 110 Hz. If we take into account non-sinusoidal form of feeding voltages signals then we shall have frequency range from 10 Hz to 700 Hz. As the NVA-55 motor bearing failures are significant, it is assumed that a contributing factor is the cyclic alternating load on the electromagnetic torque ripple causing metal fatigue failure. Proposed to use the AC variable frequency drive based on autonomous voltage inverter with pulse-width modulation control for feeding an auxiliary induction electric machines. This ensures symmetry and three-phase voltage stabilization that provides a constant sign for the electromagnetic torque of the motor with low ripple, shifted to higher frequency range.