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.

Partial resonant AC link converter: A highly reliable variable frequency drive

Abstract: In this paper a soft switched ac link ac-ac converter is employed as a variable frequency drive (VFD). The proposed configuration is a reliable, efficient, and compact converter with unity power factor at the input side. It is, in fact, a partial resonant converter i.e. only a small time interval is allocated to resonance in each cycle. Hence, while the resonance facilitates zero voltage turn on of the switches and soft turn-off, the LC link has low reactive ratings and low power dissipation. Due to the soft switching of the switches, the switching frequency can be increased and the high frequency of the link minimizes the size of the passive components. Both buck and boost operations in forward and reverse directions are feasible through this converter. Moreover, this converter is capable of increasing and decreasing the frequency over a wide range. Other than regulating the output current pulses to control the speed of motor the control algorithm also controls the input power factor and therefore no external power factor correction circuitry is required. In this paper field-oriented control scheme is applied to the proposed VFD for controlling the speed of the motor. Both simulation and experimental results are included in this paper to verify the performance of the proposed VFD

Smart Induction Motor Variable Frequency Drives for Primary Frequency Regulation

Abstract: This article proposes an induction motor variable frequency drive to investigate its potential in handling smart grid's frequency. This can thus mitigate the grid reliance on expensive power plants. To this end, a primary frequency controller is presented enabling the drive to reduce its power in proportion to grid frequency drop. The dynamic limitation of the drive due to load's inertia is considered through a motor's speed rate limiter. Moreover, an appropriate inertia emulator is proposed for the smart drive by inspiring the inertial response of a direct-on-line motor. The impacts of speed rate, maximum reserve power and motor driven load's inertia on dynamic behavior of the smart motor load during the frequency support are addressed. Besides, the effectiveness of the smart drive's contribution in primary frequency regulation of the IEEE 39-bus test system is explored. In this regard, a critical droop coefficient that guarantees the maximum reserve power delivery for the smart drives is analytically derived. Finally, the proposed approach is extended to include the critical droop derivation for a set of smart drives with different sizes and priorities to rank their participation in primary frequency regulation process.

Variable frequency drive for AC synchronous motors with application to pumps

Abstract: Two apparatuses are disclosed for controlling the speed of an AC synchronous motor-pump utilizing a series of stepped voltage pulses at the driving frequency. The first apparatus is an isolated variable frequency drive comprising step-down transformer 100 , full wave rectifier and filter 101 , micro-controller 108 , driving-voltage array generator 102 , gate driver 107 , inverter bridge 103 and step-up transformer 104 . The second apparatus is a non-isolated high voltage variable frequency drive comprising full wave rectifier and filter 201 , low voltage, dual output power supply 205 , micro-controller 208 , driving-voltage array generator 202 , gate driver 207 and inverter bridge 203 . Methods are given to determine voltage array values and pulse times to generate a stepped voltage approximation of a sine wave driving waveform.

Power supply system and method with remote variable frequency drive (VFD)

Abstract: In at least some embodiments, a system includes a first remote tool. The system also includes a variable frequency drive (VFD) coupled to the first remote tool, wherein the output of the VFD powers the first tool and wherein at least part of the VFD is in situ with the first remote tool.

Investigation of Energy Savings on Industrial Motor Drives Using Bidirectional Converters

Abstract: Motor drives is a widely used technology, offering many advantages, such as exceptional speed control and flexibility. Improvement of reliability and efficiency has become a great research interest. Toward this direction and considering the major recent developments in supercapacitor technology, the use of bidirectional energy recovery converters has been introduced in various industrial applications. In this paper, the regenerative braking of a three-phase induction motor controlled by a variable frequency drive will be analyzed and the portion of kinetic energy that can be recovered will be calculated. The main contribution of this paper is a methodology for the estimation of the energy savings that can be achieved from the use of such an energy recovery feature. In addition, the optimum braking duration that maximizes the recovered energy will be investigated. The analysis presented in this paper has been validated experimentally and the results are discussed.