Control Engineering Motors, Drives, & Motion Control Newsletter for May 2003



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SERCOS update: 3rd-generation standard coming

Various communication methods compete in the rapidly developing world of motion control. One of them is SERCOS (SErial Realtime COmmunication System), which specifies an all-digital interface for motion controllers, digital drives, and other system components. Based on fiber-optic ring architecture, it now offers message transmission rates up to 16 Mbps. SERCOS has strong supporters as well as detractors.

Recently announced by Interest Group SERCOS interface (IGS), following its annual members' meeting at Hannover Fair 2003, is a new initiative called ''Next Generation SERCOS'' (NGS), which intends to move SERCOS more in the direction of Industrial Ethernet.

SERCOS interface (IEC 61491) claims ''very high performance with guaranteed real-time behavior,'' due to its ''efficient communication protocol,'' combined with the collision-free time division multiplex access (TDMA) procedure. As an example of capabilities, Peter Lutz, managing director of IGS (Stuttgart, Germany), says SERCOS can control and synchronize up to 40 motion axes in hard real-time using a cycle time of 1 ms, while maintaining jitter below 1

According to Lutz, SERCOS' capabilities make it ''the dominant solution'' compared to such drive communication standards as Profibus and CAN. He further compares SERCOS to ''Fast-Ethernet'' based approaches, stating that ''despite a gross transmission rate of 100 Mbps-[they] very often achieve no better performance and furthermore reveal limitations with regard to their real-time behavior.''

IGS announced that the following developments would be started within the Next Generation SERCOS initiative:

  • Improving ease of integration by support of higher protocols from office and fieldbus communication (e.g., TCP/IP, Profibus, and CIP).

  • Improving performance by introducing higher transmission speeds.

  • Improving interoperability of control and drive components by defining ''motion control'' profiles and developing associated test suites to assure conformance.

  • Cost reduction by applying appropriate technology standards.

IGS plans to present Next Generation SERCOS, and start the specification and development work at the SPS/IPC/Drives trade show in Nuremberg in November 2003. Backward compatibility will receive ''careful attention to protect the investments of users and suppliers and to allow an uncomplicated migration to the new technology,'' says IGS.

For more information, visit or

Compact dynamometer serves as teaching tool

Compact dynamometer holds top shaft speed to 4,000 rpm and power output to 200 W (400 W momentary).

Do you need help understanding the dynamics of electric motors under operating conditions? A new compact dynamometer available from Motorsoft Inc. (Lebanon, OH) may be just what you have been seeking.

The dynamometer was originally developed for the University of Minnesota's Electric Drive Laboratory as a teaching tool for user engineers and students to illustrate operating characteristics of various motors with their associated drives.

Weighing just 35 lb, the ''dyno'' is available in kit form to simplify usage. The kit comes with various motors of the same general frame size that mount interchangeably to a calibrated permanent magnet (PM) dc generator, which serves as the system's torque-loading device. Three 80-mm diameter motors-brush dc, 3-phase ac induction, and PM brushless-make up the base kit. Except for the brush dc version, all motors are fitted with 1,000 line optical encoders. Optional 3-phase switched-reluctance and synchronous-reluctance test motors and a torque transducer with digital readout complete the dyno system. For user safety, the motors operate at 42 V dc maximum.

Motorsoft is the sole sales agent for the dynamometer. Base kit pricing is $4,150 (quantity 1-3), with the optional motors available for an extra $925 each. For more information and other prices, visit the Motorsoft web site .

Companies in motion

BEI Technologies, Inc. (Ventura, CA)-an established manufacturer of electronic sensors, motors, actuators and motion control products-and ThinGap Motor Technologies (Ventura, CA), an innovative motor technology company, recently announced a ''strategic supply and distribution agreement.'' The pact intends to develop, produce, and market advanced motor products using ThinGap's patented ''wireless'' and slotless electromotive coil technology that is said to uniquely focus a motor's magnetic forces, allowing for better efficiency and higher power density.

According to the agreement, ThinGap will apply BEI optical encoders and drive electronics for specific motor control and servo (closed-loop) applications. BEI will significantly supplement ThinGap's manufacturing capacity with its high volume, automated motor production.

ThinGap was a recipient of Control Engineering's 2002 Editors' Choice Award for its TG3600 Series slotless, brushless PM motors. To read about that, click here .

A.O. Smith Electrical Products Co. (Tipp City, OH), Siemens Energy & Automation (Alpharetta, GA), and TECO-Westinghouse (Round Rock, TX) recently became the latest sponsoring members of Motor Decisions Matter (MDM)-a national campaign that promotes the crucial aspects of motor management and so-called ''NEMA Premium motors.'' MDM members include motor manufacturers, electric utilities, government agencies, and trade associations.

The campaign focuses on management plans for motors, including what commonly should be decided before motor failure occurs. MDM helps ensure motor availability and lowers downtime and energy costs. Motor Decisions Matter applies life-cycle costing methods to determine whether motors should be repaired or replaced before they fail, and also when to install energy-efficient motors.

The Consortium for Energy Efficiency (CEE, Boston, MA) coordinates the Motor Decisions Matter campaign.

Schneider Toshiba Inverter SAS, the 60%-40% joint venture between Schneider Electric of France and Toshiba Corp. of Japan is bearing fruit. The joint venture was formed around mid-2000 and has the goal to accelerate development and manufacture of ac adjustable-speed drives in the 0.1-630 kW (0.13-840 hp) range.

Now the alliance has opened subsidiaries in Suhzou, China, and in Houston, TX. Schneider Suhzou Drives plans to manufacture and supply certain models of Schneider's Altivar adjustable-speed drives (ASDs) to the local Chinese market. ST Inverter America Inc. in Houston will focus on research and development, as well as the production of new lines of industrial ASDs. Two existing subsidiaries of the alliance with marketing, development, production, and purchasing functions are Toshiba Schneider Inverter in Japan and Schneider Toshiba Inverter Europe in France.


Lin Engineering's Size 11 step motor provides holding torques in the 9.2-16.6 oz-in. range.

Motor ''briefs''

Innovations and enhancements in electric motors continue to reach the market, although some call motors ''commodity'' items. Here's a recent sampling of motors. Visit the manufacturers' Web sites for more information.

Two-phase, NEMA 11 size step motors from Lin Engineering (Santa Clara, CA) give you downright miniature sizes at a 1.062-in. square profile and lengths of 1.24 to 1.99 in. One model in this 1.8

Optional 2,048-line quadrature encoder with 300-kHz frequency response is available with Servo Magnetics' motor. ê

Lo-Cog Series 8000, 9000, and 14000 brush-commutated dc servo motors from Pittman (Harleysville, PA) achieve speeds up to 10,650 rpm and peak torques up to 410 oz-in. These motors feature 7-slot or 11-slot skewed armature designs to minimize magnetic cogging at low speeds. Diamond-turned commutators ensure maximum brush life.

Danaher's T-Series NEMA 23 step motors' square frame optimizes the magnetic circuit for added performance.

Low rotor inertia contributes to high response and high torque/size ratio in Servo Magnetics Inc.'s (Canoga Park, CA) compact brushless dc motor that produces peak torque of 22.4 oz-in. from a 2.33-in. OD x 0.635-in. long unit. Typical current consumption is 200 mA at 10 V and a speed of 4,300 rpm.

Danaher Motion Co./Pacific Scientific (Rockford, IL) introduced T-Series NEMA 23 high torque 1.8ngs.

Wanted: Your input to 2004 Editorial Calendar

Soon, we will meet to formulate Control Engineering's Editorial Calendar for 2004. If you have some thoughts or suggestions on what you would like to see covered in the Motors, Drives & Motion Control sector, please send them along for consideration to

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