Showing papers on "Variable-frequency drive published in 2002"

Speed control for a pumping system

Abstract: A wastewater pumping system includes a centrifugal pump operatively connected to an electric motor via a coupling. The speed of the electric motor is automatically varied responsive to the head or load realized by the pump of the system as it varies with the composition of the slurry mixture. A variable frequency drive is operatively connected to the motor and the electrical power supply that affects a shift or change in electrical frequency delivered to the electrical motor so that the speed of the motor and consequently the pump is varied. This allows the electrical power deliver to the system to remain substantially unchanged for varying loads realized by the pump.

Electronic expansion valve control for a refrigerant cooled variable frequency drive (VFD)

Abstract: A control system for a refrigerant cooled variable frequency drive (VFD) for a chiller includes a controller which controls an electronic expansion valve to attempt to maintain a heat sink for the variable frequency drive within its design operating range. When the controller is unable to maintain the heat sink within its design operating range, a load on the chiller is reduced, either by reducing the frequency of the variable frequency drive, or if the chiller includes a compressor with internal guide vanes, by partially closing the guide vanes. The power rating of the VFD can thus be optimized based on its heat generating components operating at a controlled condition, unlike an air-cooled device which is dependent on the ambient environment.

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.

Clean power common buss variable frequency drive system

Abstract: A N pulse variable frequency drive for driving two or more motors that is the combination of two or more variable frequency drives with each drive driving an associated one of the two or motors One application is a decanter centrifuge which has a main motor to drive the bowl and a back motor to drive the conveyor One of the two variable frequency drives drives the main motor and the other drive drives the back motor The variable frequency drives are connected to a common buss and to a N pulse phase shifting transformer

Universal escalator control system

Abstract: The present invention provides a control system designed for use in either new or existing escalators or moving walkways. The control system is comprised of a main controller and a variable frequency drive. The main controller is attached to the variable frequency drive which controls the speed of the motor based upon various environmental changes, such as passenger load and safety conditions. The control system of the present invention utilizes motions sensors, time relay switches, proximity switches and other electromechanical detectors as intelligence to detect faults and to control and vary the speed of the motor through the variable frequency drive.

Chilling system and method

Abstract: A chiller system comprises a chiller, a burner, a first variable frequency driver and pump, a second frequency drive and pump, and a feedback system. The chiller has a chilled water input and a cooling water input and the burner is coupled to the chiller. The first variable frequency drive and pump is coupled to the chilled water input. The second variable frequency drive and pump is coupled to the cooling water input. The feedback system is coupled to the burner, the first variable frequency drive, and the second variable frequency drive. The feedback system capable of measuring a characteristic of the burner that is proportional to the cooling load of the chiller system and transmitting a signal corresponding determined characteristic to the first and second variable frequency drives.

Energy economizer with accumulator for variable frequency drive hydraulic elevator

Abstract: The utility model discloses an energy saver of a frequency conversion drive hydraulic elevator adopting an energy storage unit An energy storage unit loop and an energy storage unit oil refilling loop are arranged in a main loop and a load loop in the normal frequency conversion hydraulic elevator A main loop motor, a big pump/motor and a small pump/motor of the energy saver unit and the energy saver form a pressure-energy converter When the elevator moves upwards, pressure stored in the energy saver is converted into the mechanical energy which acts on a motor shaft of the main loop, to provide an addition torque; when the elevator moves downwards, potential energy and kinetic energy of the elevator are converted into mechanical energy and pressure to stored in the energy saver to realize conversion and storage of the energy , and the output torque of the motor is reduced

Magnetically Coupled Adjustable Speed Drive Systems

Abstract: Adjustable speed drive (ASD) technologies have the ability to precisely control motor system output and produce a number of benefits including energy and demand savings. This article examines the performance and cost effectiveness of a specific class of ASDs called magnetically coupled adjustable speed drives (MC-ASD), which use the strength of a magnetic field to control the amount of torque transferred between motor and drive shaft. The MagnaDrive™ Adjustable Speed Coupling System (referred to hereafter as the MagnaDrive Coupling) uses fixed rare-earth magnets and varies the distance between rotating plates in the assembly. The PAYBACK® Variable Speed Drive (referred to hereafter as the PAYBACK Drive) from Coyote Electronics uses an electromagnet to control the speed of the drive. Laboratory testing was conducted at the Motor Systems Resource Facility at Oregon State University to evaluate performance for the MagnaDrive, PAYBACK, and a common variable frequency drive (VFD) when connected to a 5...

Well pump motor driver control apparatus and method

Abstract: The present invention relates to a circuit for providing conditioned alternating current to a motor for running a well pump reciprocating motor which experiences uneven torque. A system is provided for conditioning the primary electrical supply 310, bussing the conditioned primary service 318 to a variable frequency drive apparatus VFD 336 which alters the line frequency of the alternating current to a controlled frequency to change the speed of the motor in response to a signal received from a well controller 330, and, if the system begins to inductively regenerate current when the speed of the rotor exceeds the line frequency from the drive, to condition and shunt the excess direct current R to the primary supply side 318 of the variable frequency driver where it may be reused.

Fan and pump systems: markets and programs

Abstract: Since fan and pump systems provide large opportunities for energy savings and account for about 40% of motor systems energy use (see Figure 1), they are a prime target for energy efficiency efforts. However, most of the available savings from fan and pumps systems require an understanding of the marketplace and good application-specific engineering, and cannot be obtained in a “cookie cutter” fashion. Because fan and pump energy use varies as approximately the cube of motor speed while flow varies directly, small changes in motor speed can have large impacts on energy use. Motor speed can be changed by varying the drivetrain (e.g., different belts and pulleys), through staging multiple fans or pumps, or through the use of an adjustable speed drive (ASD), also know as a variable frequency drive (VFD). Most end-users (and even many of the consulting engineers they hire) often lack practical knowledge regarding how best to optimize systems. Furthermore, optimization can be a time-consuming process, and time is something most customers are short of.

Machine tool with servo drive system

Abstract: In a multi-spindle lathe for machining bar stock the spindles are driven by a variable frequency drive motor. A first multi-cam shaft is arranged parallel to the spindle axes to drive first machining tools, such cam shaft also driving a mechanism to index the spindles through a plurality of work stations. A second multi-cam shaft is arranged perpendicular to the spindle axes to drive second machining tools. The first and second cam shafts are driven via gearing from a servo motor. The variable frequency motor and the servo motor are controlled by a programable logic controller.

Designing filter for harmonic suppression for industrial plant as per IEEE-519 standard

Abstract: This paper discusses the application of revised IEEE 519 standard to the tool manufacturing industry where the combination of variable frequency drive (VFD) and induction furnace loads are used To control the harmonic current injected into the power system, conditions are developed as a function of VFD and induction furnace characteristic, overall plant loading level, power system characteristics and power factor correction requirements Based on these parameters, filter design procedures are presented for controlling the harmonic currents