Appliance Design - October 2007 - (Page 22)

MOTORS DOUBLE DUTY Fig. 1. Air-conditioning design platform. Technology platforms simplify dual motor control. A by aengus murray Aengus Murray is director, iMotion Products, Energy Saving Products Group, International Rectifier Corp., El Segundo, Calif. 22 applianceDESIGN October 2007 dvances in power and digital control silicon technology over the past few decades have enabled a continuous improvement in motor-drive technology. When permanent-magnet, brushless-motor drives were first introduced to the market more than 20 years ago, the control algorithms were implemented using a combination of analog amplifiers and logic components. Today, highly integrated, mixed-signal controllers enable the implementation of complex control algorithms that maximize the efficiency of permanent-magnet AC motors. Japanese air-conditioning manufacturers recently started switching from sensorless control based on back-EMF sensing, to sensor-less, field-oriented control based on current feedback. Field-oriented control (FOC) with current-angle phase-advance maximizes the efficiency of interior permanentmagnet motors, providing an efficiency gain of almost 5 percent. The switch from trapezoidal to sinusoidal control also minimizes torque ripple in order to reduce acoustic noise in the fan motor. A recently introduced mixed-signal control IC can simultaneously run both the compressor and fan motors in an air conditioning system. A combination of highly optimized hardware control blocks and a configurable control sequencer enables rapid execution of complex motor control algorithms. The IC is one element in an appliance design platform that includes all the power and control silicon needed to drive the fan and compressor motor in an air-conditioning system. The same IC can also be applied to the latest energy-efficient laundry systems in Japan that use an energy-saving heat pump in the drying cycle. Air-conditioner platform The circuit schematic in Fig. 1 includes the major components in the outdoor unit controller for an air-conditioning system. The mixed-signal, motor-control IC drives the compressor motor, the fan motor, and the power factor correction circuit. The IC integrates three major functions: the Motion Control Engine (MCE), the Analog Signal Engine and an 8-bit microcontroller. The MCE executes the motor control algorithms, while an independent 8-bit microcontroller core implements the application functions. The sensorless, field-oriented control algorithm derives all the required motor information from the currents flowing in the DC link shunts. This avoids the need for position sensors on the motor shaft and isolated current transducers in the power inverter circuit. www.applianceDESIGN.com http://www.appliancedesign.com

Table of Contents Feed for the Digital Edition of Appliance Design - October 2007

Contents Editorial Shipments/Forecasts News Watch Applying Powder Coatings to Plastic Parts is No Longer a Pipe Dream New Technology Platform Provides the Ability for a single IC to Control Two- Motors in a Single Appliance, Simplifying Motor Control Design Advanced Motor-Control Techniques have Become More Accessible to a Wider Array of Appliances, Helping to Improve Efficiency and Reduce Noise Adding USB Host Capability to Appliances Permits In-Field Programming and Acquisition of Test Data ZigBee Modules Make it Easier to Design Wireless Connectivity into Applications New Concepts such as Rapid Tooling and Rapid Injection Molding Provide Stepping Stones Between Prototyping and Full Scale Production A Number of Factors and New Developments Affect the Decision on Whether to Build Prototypes In-House or Outsource to a Service Bureau DesignMart Advertiser’s Index Association Report: CEA

Appliance Design - October 2007

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