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.

Control system and method for an overhead bridge crane

Abstract: Included herein is a system and method for controlling a velocity vector of an overhead crane. A motor is attached to the crane and is positioned to move the overhead crane and has an output vector including a rotational direction and a rotational speed. A variable frequency drive is positioned to transfer voltage and current at a frequency to the motor. A processing unit converts the output vector to an amount of voltage and current at a given frequency and can instruct the variable frequency drive to send a frequency to the motor at a frequency substantially equal to the frequency at which the motor is presently rotating. This creates a speed match for the motor reducing spikes during operation of the motor and substantially eliminates open circuit decay. A hydraulic brake operates in connection with the processing unit and the variable frequency drive to slow the crane without driving the motor into the brake.

Variable frequency drive device

Abstract: The utility model provides a variable frequency drive device used for a first motor, a second motor and a third motor The variable frequency drive device comprises a first frequency converter, a second frequency converter, a circuit breaker and a plurality of disconnecting links, wherein the first frequency converter is electrically connected with the first motor through a first disconnecting link, the second frequency converter is electrically connected with the second motor through a second disconnecting link, the circuit breaker is electrically connected with the third motor, and the plurality of disconnecting links are respectively connected between the first frequency converter and the third motor, the second frequency converter and the third motor, the circuit breaker and the third motor, the circuit breaker and the second motor as well as the circuit breaker and the first motor The variable frequency drive device can meet the requirements of regular alternation of the three motors, working frequency standby and equilibrium running, thereby the using flexibility and utilization ratio of the motors being increased

Impacts of Barrier Shape on Torque Ripple and Saliency in Synchronous Reluctance Motor for Solar Water Pumping

Abstract: The rotor structure in synchronous reluctance motor (SyRM) doesn’t have any cage, magnets and windings resulting in a rugged, reliable and lower cost of manufacturing. The rotor construction in SyRM comprises of only barriers, which play prominent role in torque shaping, torque ripple content and power factor. The impact of the air barrier shapes on the performance of the motor is studied. The main aim of the research is to analyze the effect of flux barriers shapes on average torque, torque ripple, saturation, cross saturation and saliency ratio of the machine. In solar water pumping, the torque ripple is a serious concern, especially in submersible pumps. Moreover, the power factor is a prime aspect in deciding the rating of variable frequency drive for Maximum power point tracking (MPPT). A 4pole, 100Hz synchronous reluctance motor with 24 stator slots is chosen for study and analysis is done using finite element analysis (FEA).

Cost-Effective Control Scheme for Reduction of Torsional Torque Oscillations in Starting Large Induction Motors

Abstract: This article presents a cost-effective variable frequency drive for starting and operating large three-phase squirrel cage induction motors. The proposed drive employs the constant V/F control scheme, which regulates the rotor frequency such that it is always kept below a predetermined value. This has the effect of drastically reducing the motor shaft torque oscillations and significantly limiting the maximum value of the motor line current. In addition to its simplicity and hence cost-effectiveness, the proposed scheme is shown to be capable of (i) reducing the shaft torque oscillations to approximately 22% of that of the direct on-line start of the large motor, and (ii) limiting the motor line current to approximately 36% of that of the direct on-line start value.

System for operating a three-phase variable frequency drive from an unbalanced three-phase or single-phase ac source

Abstract: A variable frequency motor drive comprises a converter including a rectifier having an input for connection to an AC power source and converting the AC power to DC power. A DC bus is connected to the rectifier circuit. At least one bus capacitor is across the DC bus. An inverter receives DC power from the DC bus and converts the DC power to AC power to drive a motor. A controller is operatively connected to the converter. The controller comprises a speed control controlling the inverter responsive to a speed command to maintain a desired motor speed. A speed foldback control measures DC bus ripple voltage and regulates the speed command responsive to the measured DC bus ripple voltage.