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Controls/MCUs??

Manage design resources for industrial apps

Posted: 16 Nov 2007 ?? ?Print Version ?Bookmark and Share

Keywords:design resources for industrial applications? chip-level architecture? platform approach for industrial control?

In today's fluid and interconnected geopolitical environment, every micro- or macroeconomic event can lead to significant increases in energy costs. As costs continue to creep upward, energy efficiency in applications previously taken for granted is becoming critically important to the conservation of limited resources. Many of these applications such as white goods are ubiquitous that we rarely notice themexcept when they malfunction and need to be replaced or repaired.

At the lower end of the spectrum, it may be more cost-effective to replace than to repair. However, this usually entails replacement with more traditionally designed equipment that may not be energy-efficient. To meet some of the emerging regulatory requirements for energy efficiency, OEMs must be able to produce higher-end (and more costly) models that incorporate more energy-efficient design methodologies at cost points only slightly above the traditionally designed low-end and midrange products. Also the issue of international regulatory variations among countries that mandate specific or unique models for different geographic locales must be addressed.

Platform approach
To better manage scarce design resources and attain economies of scale, OEMs need solutions that enable customization of a small number of platforms with common building blocks, so that the regulatory and geographically unique models may require only minor variations in components and/or firmware. This platform and modular approach requires a different engineering skill set from those used to build older-generation appliances.

Previous generations of products usually incorporated a simple user interface, such as an on/off switch (pool pumps), a rotary dial (ovens, refrigerators, freezers and A/C units) or a mechanical timer (washers). All of these units could essentially be manufactured with off-the-shelf components.

Today's leading-edge designs incorporate LCDs, MCUs and, in some cases, Internet connectivity, to enable remote diagnostics or "early warning" preventive maintenance. The primary movers (motors for compressors, pumps or rotation) are becoming more complex, with electronically commutated (EC) motors replacing capacitive-start or split-phase AC motors.

Besides the energy-efficiency gains possible by transitioning to EC motors, secondary benefits can be achieved, such as lower operating noise, reduced vibrations and increased reliability. To achieve them, OEMs must become more adept at modeling the application requirements and quickly implementing the results.

Programmable, modular platforms may enable OEMs to provide target units for different segments with minimal effort and cost, with some of the key differentiation residing strictly in the MCU firmware.

IMS Research predicts that the percentage of major home appliances using an inverter-based approach to motor control would increase from 10 percent in 2005 to 20 percent by 2011. The shift is expected to be most pronounced in washing machines and room air conditioners.

By taking advantage of the integration provided with today's MCUs, expanding the engineering team's skill sets to include software/firmware development and migrating to more energy-efficient modular platforms, OEMs can meet the industry's changing regulatory requirements while reducing time-to-market, increasing product differentiation, lowering manufacturing costs and providing the end consumer with more reliable and cost-effective solutions.

Energy savings
Other industrial segments affected by the need for energy efficiency include industrial-automation motor applications and commercial heating, ventilation and air conditioning (HVAC) apps. With industry migrating to EC motors, further energy savings are possible with improvements to application quality and reductions in usage costs. Manufacturing operations are prime candidates for energy-efficiency improvements, and can benefit from the longer life as well as preventative and preemptive maintenance made possible with the newer generations of integrated motor controllers.

The automotive and pharmaceutical industries may have downtime costs totaling hundreds of thousands of dollars per hour. The sustained energy savings as well as operational savings can quickly pay for the installation of more advanced motors and controllers.

More than 60 percent of energy usage in manufacturing applications is attributed to the motor and is dissipated as heat, vibration, noise and the actual work performed by the motor. Since motors are most efficient when fully loaded, appropriate sizing of the motor to the application is critical for optimum energy consumption and up-front cost reduction. But older motors tend to be oversized for the application, so that both the up-front and sustained operational costs are less than optimal.

IMS Research predicts that the percentage of major home appliances using an inverter-based approach to motor control would increase from 10 percent in 2005 to 20 percent by 2011.

For most motors (whether AC induction or permanent magnet), motor efficiency is seriously reduced at operational loads less than 40 percent of full load (FL). Since almost 44 percent of all motors used in manufacturing applications operate below 40 percent of FL, significant energy and up-front cost savings are possible by transitioning to the newer generation of motors and controllers.

Variable-speed capability can reduce noise in HVAC and other apps by reducing speed to match the load requirements. If the load was reduced in older HVAC condenser apps, the system would deactivate one or more fans to minimize noise. Significantly higher noise reductions are possible if all the fans are kept running but the speed is decreased to match the load requirements.

Another aspect of motor applications that is transitioning to an integrated SoC approach is overload protection, which was previously performed with bimetallic circuit breakers. The device must follow specific thermal profiles and specific trip curves in addition to allowing a certain amount of end-user customization.

Teridian Semiconductor has developed a single-converter technology suited for the high-accuracy current measurements required in such applications. One such device is the 71M6403 electronic trip unit for circuit-breaker and protection relays. It incorporates a 22bit delta sigma ADC, six primary current sensor inputs and one secondary input, digital temperature compensation, a precision voltage reference, a 32bit programmable computation engine, timers, a real-time clock, two UARTs and a single-cycle execution 8bit MCU.

Programmable solution
With a built-in digital di/dt integrator, the programmable device supports either current-transformer or Rogowski coils for any or all input channels, and provides instantaneous or delayed overcurrent protection and other protection functions. The device may be configured to support conventional or custom protection algorithms that fit specific load configurations in the field.

The programmable 32bit compute engine receives and processes all sensor data from the 22bit ADC while running independently of the 8bit MCU, which handles higher system-level management and communications. This separation of the mixed-signal metrology subsystem and management subsystem eliminates external interruptions and unnecessary processing overhead.

Another Teridian offering, the 71M-8100 measurement controller, has three inputs to sense and control secondary parameters such as temperature, vibration, flow, pressure and humidity.

Further innovative opportunities for enhanced industrial automation, protection and control can be addressed with the same fundamental chip-level architectures.

- Tom Kapucija
Marketing Director
Teridian Semiconductor Corp.




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