HVAC Control in the New Millennium.pdf - HVAC.Amickracing

HVAC Control in the New MillenniumFeedback DevicesWhile more sensorless systems may be appearing, many motioncontrol systems will continue to need feedback devices. These aremostly encoders and there will be continuing refinements in these. Incrementalencoders will evolve into networkable smart devices that takeover tasks now done by absolute encoders.Since they will be tied into the network, they will always be powered.If a position is changed when the machine is powered off, they willstill be able to monitor position and the machine control server will beable to maintain an absolute position.The newer encoders can also function in temperatures that traditionallyhave called for resolvers. BEI Motion Systems, for example, hasencoders that operate at 105°C, and Admotec has magnetic encodersthat work from -30 to 90°C.Sometimes a feedback device is not used. Semipower Systems’IndexBlok drive module can position 1 to 20 kW three-phase motorswith up to 16-bit resolution per electrical cycle of the motor with nofeedback device. It gets its information from the motor itself and processesit with special software.Linear encoders continue to improve. Danaher Controls’ DynaparLR/LS inductive linear encoder provides resolutions to 0.25 micronwithout the use of glass scales.Feedback devices will undergo more changes besides the additionof network capability. Conventional encoders will be replaced by lasersensors and fiber-optic sensors in the future.Trends in Motor TechnologyThe move to integration involves building all the electronics intothe motor. Animatics has done this with its SmartMotor line. The integrationof controls into the motor package will be paced by advances inpower control devices. Smaller, more intelligent and more efficient motorcontroller packages will operate both brushless and stepper motors.Motors and the mechanical components associated with them willgain in performance and decrease in price. This will be due partly toimprovements in materials, especially magnetic materials and insulationsystems. Servo technology is becoming more easier to use and tune.Brushless servo motors and amplifiers will show a continuing©2001 by The Fairmont Press, Inc. All rights reserved.