Project Analog - August 2008 - (Page 17)

mcP9800/1/2/3 TEmPEraTurE SENSorS shows the simple layout of a highefficiency drive. The variable-frequency drive (VFD) is the simplest and most common three-phase ACIM. Costing just tens of dollars per kilowatt, these controls are being used in applications where a motor drive was not cost-effective even a decade ago. Field-oriented control (FOC) algorithms allow the VFD to precisely control the motor’s stator field such that it always leads the rotor field by 90, providing the optimal magnetic configuration for efficiency. Fluxvector is another name for this algorithm. In pump and ventilation drives up to 50% annual energy saving can be realized by using VSDs with ac induction motors. VSDs also often allow the elimination of mechanical gearboxes, pulleys, belts, and other hardware. BLDC controls are available with both the trapezoidal and newer sinusoidal modulation methods. The need for magnetic Hall sensors to resolve the rotor’s position for electronic commutation has been removed by sensorless algorithms which approximate the rotor’s position by measuring the back-EMF on the unexcited motor windings between conducting phases. The common availability of these drives has lead to decreased brushless motor cost. Switch reluctance motors provide excellent starting torque and high-reliability, and are simpler to construct than even the ACIM. Unfortunately, the widespread lack of understanding of this motor topology has led to it being misapplied and it has had a low adoption rate. Many existing SR systems suffer from excessive torque ripple and are not acceptable for use in residential or industrial applications. Sensorless control techniques and dedicated power modules are now available that will allow these motors to be commutated in a fashion that will allow their cost/performance ratio to be appreciated. Although VSDs can simplify a mechanical system and enhance a The MCP980x digital temperature sensors convert temperatures between -55°C and +125°C to a digital word. They provide an accuracy of ±1°C maximum and feature a user programmable resolution between 9 and 12-bits. These devices also allow the user to configure the power saving Shutdown and One-shot modes, temperature alerts, and hysteresis limits. Click here for more information on the MCP9800/1/2/3 system’s reliability and long-term efficiency, some characteristics of the traditional drives prevented them from being considered as effective solutions in fixed-speed applications in the past. Advanced control algorithms combined with state-of-the-art electronics are now able to overcome most of these concerns. For example, Direct Torque Control algorithms allow an ACIM to perform tasks that were previously in the brush dc motor’s domain due to their improved response to dynamic changes in load and improved lowspeed performance. Recently, the cost of an ACIM and control has begun to approach that of a simple brush dc motor and control. Contents Viewpoint Gate Drive Schemes for Motor Control Applications Considerations When Selecting the Proper MOSFET Driver Power Modules for Variable-Speed Motor Control Analog news Microchip analog page Motor Control Design Center Sample center microchipDIRECT Reference designs/ app notes 17 · PrOjECT ANAlOG · VOluME 2 / NuMbEr 5 Technical training http://www.microchip.com http://www.microchip.com/ParamChartSearch/chart.aspx?branchID=9001&mid=11&lang=en&pageId=79 http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=79&redirects=analog http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=79&redirects=analog http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=2125¶m=en026178 http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=2125¶m=en026178 http://sample.microchip.com/Default.aspx?testCookies=true http://www.microchipdirect.com/catalogselection.aspx?returnURL=default.aspx http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1469&filter1=function&redirects=appnotes http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1469&filter1=function&redirects=appnotes http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1423

Table of Contents Feed for the Digital Edition of Project Analog - August 2008

Project Analog - August 2008 Contents Viewpoint About Project Analog Sponsor Gate Drive Schemes for Motor Control Applications Considerations When Selecting the Proper MOSFET Driver for Your Application Power Modules for Variable-Speed Motor Control Efficient Motor/Controls Save Terrawatt-Hours/Year Analog News Contact Microchip Treelink Microchip Advanced Parts Selector (MAPS)

Project Analog - August 2008

For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.