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.

Energy Saving Mechanism Using Variable Frequency Drives

Abstract: Many industrial applications require variable flow control of fluid (air, chemical gases, water and liquid chemicals). The traditional method of such flow control is to use an induction motor at constant speed with 50-Hz power supply and then control the flow by means of a throttle. Many fixed-speed motor load applications that are supplied direct from AC line power can save energy when they are operated at variable-speed, by means of VFD. Such energy cost savings are especially used in variable-torque centrifugal fan and pump applications, where the load's torque and power vary with the square and cube, respectively of the speed. This change gives a large power reduction compared to fixed-speed operation for a relatively small reduction in speed. Also by Using a variable frequency drive to control the fluid flow with a fully open throttle saves a considerable amount of power. As most of the drives operate at part load most of the time, the accumulated energy saving or the corresponding financial benefit, may be substantial over a prolonged period of time. Because this type of fluid flow control is common in industry, widespread application of variable-frequency drives with power electronics area can help in large energy conservation. The main aim of this paper is to reduce the energy consumption by the implementation of VFD and hence the proper control of fluid flows.

Variable frequency drive for a motor-generator/alternator set

Abstract: A variable frequency drive for a motor-generator/alternator set which is used to supply electrical power to computer or data processing equipment. Power failures in commercially supplied power results in aberrations and erroneous computations in computers and data processing equipment. An induction motor is used to drive a generator/alternator. The induction motor is driven below the synchronous speed of the generator/alternator and a variable speed drive increases the velocity supplied to the generator/alternator, preferably to a point above its synchronous speed. Therefore, when there is a commercial power failure, the generator/alternator remains within a desired frequency range for a longer period of time than a comparable generator/alternator driven at synchronous speed.

AC motor bypass with fault annunciation, serial communication and fault tolerant coil control

Abstract: A motor bypass is controlled by a digital signal processor (DSP) with embedded control software that allows fault detection and annunciation, serial communications between both a variable frequency drive (VFD) and a bypass controller and the bypass controller and a host computer. The use of the DSP and embedded control software further allows for contactor coil control to provide fault tolerant operation as well as fault condition detection and annunciation to the user.

Dual-frequency braking in AC drives

Abstract: Many variable frequency drive (VFD) applications require infrequent or partial braking. The use of a regenerative circuit, or of a dynamic braking resistor, adds significant cost to the VFD. This paper presents a method to obtain braking torque in nonregenerative AC drives without the need for additional power circuits. With this method, braking energy is absorbed from the rotating inertia at the applied frequency and is dissipated in the motor at a second loss-inducing frequency. Theoretical results that illustrate the usefulness and limitations of the proposed approach are given. Test results with low-voltage and medium-voltage drives are included in this paper. As compared to DC injection braking, the proposed method allows continuous estimation of motor speed and gives much higher braking torque per ampere.

Intelligent control of the regenerative braking in an induction motor drive

Abstract: This work deal with the problem related to the energy recovered in an induction motor drive. During deceleration, a regenerative braking control strategy allows the recovery of the mechanical energy stored in an inertial mass. This process involves the conversion of the kinetic energy into electric energy. The parts that compose the system are a squirrel cage induction motor variable frequency drive and controller and the mechanical system (flywheel) representing the inertia of the automobile. In order to test the performance of the intelligent control, it is compared with a conventional control scheme. The conventional control scheme is used to generate the samples of the input and output signals, which allows the identification of the dynamics of the system (plant). Also, it is used as a reference for the performance of the intelligent control.