Showing papers on "Variable-frequency drive published in 2005"

Variable speed electric drive options for electric ships

Abstract: Variable speed electric propulsion motors are operated from a variable frequency drive (VFD), which supplies power to motors at a frequency appropriate to the desired speed. These VFD's are normally very heavy and large in size. A variety of designs are commercially available but they have characteristics unsuitable for ship applications. The objective of this study was to evaluate various options for shipboard applications and to recommend designs that meet navy performance, weight and size constraints. It is possible to dramatically reduce the size and weight of the VFD by optimizing the VFD and the motor as a system, utilizing an optimal distribution voltage, eliminating distribution frequency transformers, and utilizing the weight and size reductions available with liquid cooling. Three systems were studied in detail: cycloconverters, series connected low voltage inverters, and multi-level medium voltage inverters using 6 kV class IGBT's or similar switching devices. On the basis of this evaluation, a multi-level diode-clamped pulse width modulated (PWM) drive topology is recommended for navy ships. A three phase distribution voltage of 6 to 9 kV RMS minimizes the number of series semiconductors and control complexities of the drive.

5 MW High Temperature Superconductor Ship Propulsion Motor Design and Test Results

Abstract: American Superconductor has designed, built, tested and delivered to the U.S. Navy's Office of Naval Research (ONR) a 5MW, 230-RPM, 6-pole high temperature superconductor (HTS) ship propulsion motor. The motor uses an air core armature winding and first generation HTS wire (BSCCO-2223) field winding. The goal of the motor development project was to validate the technologies required to design and build larger HTS ship propulsion motors, as well as to develop a motor production process that streamlines development time and minimizes cost. A commercial variable frequency drive is used to power the motor. The HTS field winding is cooled with G-M coolers with gaseous helium as the cooling medium in a closed cycle. The armature is cooled by MideP. The motor was delivered to the U.S. Navy in July 2003 and met or exceeded requirements in operation (up to the facility's testing limit of 2.5MW). The motor demonstrated both full torque and full speed operation in separate tests.

Cancellation of dead time effects for reducing common mode voltages

Abstract: Methods and apparatus for canceling dead time effects in the form of common mode voltages produced by a three-phase power conversion device in a rectifier/inverter variable frequency drive (VFD) system includes limiting the voltage difference between phase voltages at certain switching transition times to an amount δ, that is a function of the dead time that is specified for the switches and delaying gating signals to the switches to remove unexpected pulses produced by common mode voltages.

Engine driven power inverter system with cogeneration

Abstract: A combined heat and AC power generating system is disclosed having black start capability for the full time, simultaneous production of both electricity and heat. Heat generated within the system is captured and used for heating applications such as heating building air and tap water. The power generating system comprises an engine, generator, rectifier, variable frequency drive inverter, and inverter control electronics. The system provides improved efficiency and prolonged engine life by always operating the engine with its throttle fully open to obtain maximum efficiency and the engine is normally operated near its stall point. In this operating state the inverter control electronics adjust the power output from the inverter to control the speed of the engine. This is done by increasing the power output from the inverter when the power drawn by the load decreases. This causes the engine to operate closer to its stall point and it slows down. The power from the inverter is decreased when the power drawn by the load increases. This causes the engine to operate further from its stall point and it speeds up., The slight power changes to facilitate this operation will always be drawn from or distributed to the electric utility grid so there is no wasted power. The inverter control electronics are responsive to signals from loads such as refrigeration loads to cause the frequency of the inverter output to change to permit the refrigeration load to operate more efficiently.

Overvoltage suppression technique for variable frequency drives operating reciprocating loads

Abstract: A motor control for a reciprocating load includes overvoltage suppression. The motor control comprises a variable frequency drive (VFD) operatively connected to a power source for operating a motor to drive the reciprocating load. A sensor determines motor torque. A control unit is connected to the VFD and to the sensor and is adapted to control the VFD in a normal mode to operate the motor at a select reference frequency. The control unit predicts occurrence of a negative motor torque condition based on sensed motor torque and in response to a negative motor torque condition controls the VFD in a negative motor torque mode to operate the motor at a higher frequency than the select reference frequency to prevent the motor from entering a negative slip condition.

Method for mitigating rod float in rod pumped wells

Abstract: Rod Float Mitigation (RFM) methods for rod-pumped oil wells having a variable frequency drive which controls the speed of the motor for the pump. Each method monitors rod loads or a similar condition and takes action only when rod load drops below a predefined minimum load. A first method reduces the speed of the motor to a preset level. A second method fixes the torque level on the pump downstroke by adjusting motor speed based on a calculated gearbox torque compared to a programmed fixed limit. Another method includes a program in the variable frequency drive which includes a preferred RFM Torque Curve for the pump to follow on its downstroke. When rod float occurs, the program monitors gearbox torque and adjusts the speed to follow the predetermined RFM Torque Curve thereby mitigating rod float with minimum decrease in production.

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.

Apparatus and method for controlling compressor motor speed in a hydrogen generator

Abstract: An apparatus for producing hydrogen having compressor motor speed control. The apparatus includes a hydrogen generator for producing a product comprising hydrogen and a compression unit for compressing the product. The hydrogen generator can include a fuel processor having an oxidizer and a reformer. The compression unit has an induction motor and means for regulating the speed of the motor. The means for regulating the speed of the motor can include a variable frequency drive or soft start device having a plurality of switches and an adjustable ramp timer. A downstream unit including one or more of a purification unit, a second compression unit, and a storage unit is disposed downstream of the compression unit. A method for producing hydrogen is provided that includes generating a product comprising hydrogen in a hydrogen generator, compressing the product in a compression unit having an induction motor and regulating the speed of the motor in response to transient operations of the hydrogen generator.

The Analysis and Design of Electric Control System of Fully AC Rewinder

Abstract: The paper describes the rewinder's electric control system with AC in which a converter is used to control AC motor It discards the conventional speed adjustment with variable frequency drive and solves the technology problem of wide range speed adjustment of the discharging roll under consistent tension It achieves a better rate of performance to the cost

Design of Heat Sinking in High Voltage Variable Frequecncy Drive System

Abstract: This paper studies the design of the heat sinking in 6kV/2.5kW variable frequency drive system.Forced air cooling technology is applied in the drive system.Based on the calculation of power losses,the heat sinks are designed ac-cording to the relation between power losses and temperature rise.The scheme of air conduit is presented,which include:front air intake,sealed wind cavity and back air outtake.Each heat sink is joined into the close wind cavity separately.The experiment results show that the heat sinking is satisfied.

Washing machine with variable-frequency drive

Abstract: A conversion driver wash machine. It contains system of wash and desiccation, drive gear applying revolute force to the system of wash and desiccation, induction motor driving the drive structure and its adjustable power. Adjustable power applies power as potential U1 and frequency f1 when the system of wash and desiccation is turned on or speed is increasing. After a certain time, apply U2 and f2(U1/f1)> (U2/f2).

Economic PLC Control in Variable Frequency Drive of Paper Machine

Abstract: This paper introduces an economic and practical control project in variable frequency drive of paper machine.It uses S7-200 PLC as the core and uses the I/O and communication function to achieve the control in variable frequency drive of middle speed or low speed paper machine.This paper mainly introduces the hardware and software's design of this project and the way using S7-200 PLC to achieve speed chain and charge distribution in variable frequency drive of paper machine.

Study of Energy and Demand Savings on a High Efficiency Hydraulic Pump System with Infinite Turn Down Technology (ITDT)

Abstract: Detailed field measurement and verification of electrical energy (kWh ) and demand (kW) savings is conducted on an injection molding machine used in typical plastic manufacturing facility retrofitted with a high efficiency hydraulic pump system. Significant energy usage and demand savings are verified for the retrofitted injection molding machine. The savings are realized by electronically attenuating the torque of a positive displacement pump irrespective of the volumetric flow required by the cycle. With help of a power analyzer, power quality issues are addressed. Some voltage distortion was observed due to the harmonic currents introduced by the control algorithm of the high efficiency hydraulic system. A comparative study of electrical energy and demand savings between an injection molding machine retrofitted with the high efficiency hydraulic pump system or variable frequency drive will also be presented.