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February 26, 2008


In this issue of the Motors Newsletter from Machine Design there are articles on how to parallel LED current drivers and linear dc motors.

The products highlighted are 12-Vcd gearmotors, dc/dc converters, and large capacity ac drives.

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-- Julie Kalista

Articles

How to Parallel LED Current Drivers
As white LEDs become more pervasive, there are ever-more options for driving them. Linear constantcurrent drivers, for instance, offer low EMI, low cost, and use only a few components. Many designers favor them for low-current applications where power loss is a minor concern. If power dissipation is a problem, or if the application needs more current, you can parallel two or more drivers. Two drivers in parallel provide twice as much current and split power loss into two locations, which makes for easier heat dissipation. High-side pass elements are preferred, especially in automotive uses, because they let you connect only a single current-limited wire (chassis return) to the load. To configure parallel drivers with high-side pass elements, however, the current-sense feedback circuitry must also be on the high side, and it must be able to withstand at least the voltage the LED load creates. Thus, linear drivers pose a dilemma if they have either low-side current-sense feedback or a requirement for limited common- mode voltage on the sense inputs.
Full Article

Basics of Design Engineering: Linear DC Motors
Basics of Design Engineering: Linear DC Motors
A linear dc motor, like a rotating dc motor, generates mechanical force by the interaction of current in conductors and magnetic flux provided by permanent rare-earth magnets. It is constructed of a stator assembly and a slider. The stator assembly serves as the body and contains a laminated steel structure with conductors wound in transverse slots. The slider contains one or more sets of magnets, commutation components, a bearing surface, and its body completes the magnetic flux path between the magnets.
Full Article

New Products

12-Vdc Gearmotor
The MMP-TM55 12-Vdc GPk52-046 gearmotor works with any 12-Vdc source and requires only 7.2 A to generate full load torque, thus promoting battery life, quiet operation, and less-expensive drive electronics. The reversible gearmotor's output is 46 lb-in. continuous torque at 100 rpm and 89-lb-in. peak. The unit measures 2.14 7.2 in. and has a keyed output shaft of 12-mm diameter 25-mm long. The gearmotor mounts easily with four face-mount M5 threaded holes, equally spaced on a 40-mm-diameter B.C.
More Information:
Midwest Motion Products


Dc/dc Converter
Targeting railway and other harshduty uses, the RWD 200 dc/dc converter has a built-in redundancy diode for when two modules connect in parallel. The converter is encapsulated in a thermally conductive MIL-spec siliconrubber compound that provides immunity to shock, vibration, humidity, moisture, salt, and airborne contaminants. The unit operates at −40 to 70°C.
More Information:
Absopulse Electronics Ltd.


Large-Capacity Ac Drives
The SJ700 Series ac drives handle 250, 400, and 500-hp ranges. An improved Sensorless Vector control algorithm lets the drives develop 150% starting torque at 0.3 Hz. For verticallift applications, the SJ700's 0 Hz Domain open-loop control mode develops 130% torque at 0 Hz. Additional features include Micro Surge Voltage suppression (protects motor-winding insulation), advance trip-avoidance functions, configurable sink/ source logic on I/O, built-in RS-485 Modbus/RTU communication, and options for other communications networks. The SJ700 can be configured using a front-mounted keypad.
More Information:
Hitachi America Ltd., Industrial Systems Div.


News from MD


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Rev up your interdisciplinary design skills

What happens when a microcontroller turns on a power FET, sending a current pulse to a motor coil that develops a magnetic field which turns the rotor shaft, advancing a timing belt that drives a pair of nip rolls suspended on bearings in a web-processing operation on a form, fill, and seal machine installed on a potato chip line at a Frito Lay plant in central California? And how can you be sure that the encoders, prox sensors, and other feedback devices you plan to use will accurately see and report every relevant motion, machine state, and process condition? And will the signals get through the networks fast enough, without being corrupted, giving the controllers time to execute their algorithms as intended? It's a lot to think about, and it only scratches the surface of what many engineers grapple with today. If you happen to be one of them, then the place for you — where you can find answers and meet others with similar concerns — is www.Mechatronic-Design.com.

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With more than 200 on-demand webcasts, videos, interactive tutorials and demos available for users of any experience level, it is easier than ever to learn about the newest products and features available from National Instruments.
Begin your search here with a collection of webcasts specifically chosen for design and automation engineers.

CAD Library offers advanced CAD Resources
The Machine Design CAD Library, includes millions of configurable 2D and 3D CAD models of components and assemblies downloadable for easy use in new and existing designs. Our models are in native CAD formats. No translation required!

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UPCOMING IN-PERSON EVENTS
Design-2-Part Shows are America's longest running and most trusted events for sourcing custom parts and services. Ten shows covering the country offer OEMs, engineers and purchasing personnel the opportunity to meet job shops and contract manufacturers face-to-face.

Linear Analysis Training Class
February 11-15, 2008
Students will be shown demonstrations of how to set up, analyze, and investigate typical structures. Workshops let students put this new knowledge into practice. The important features of the FEMAP GUI are introduced and, at the same time the essentials of Nastran are explored. Emphasis during the class is on the construction of proper analysis models, and the effective use of the various solution types. Additional troubleshooting techniques are discussed, as well as the various types of common error messages generated by NEiNastran. The objective of this class is to give a solid grounding in FEA basics and good practice to enable the student to carry out real world linear static analysis.

UPCOMING WEBCASTS

Customization for the Competitive Edge
Sponsored by PTC
DATE: March 5th, 2008
TIME: 2:00pm ET

As customers shun the "take it or leave it" mentality of mass production in favor of customized product development, industrial manufacturers respond by offering more and more product options and variants. Launching a product that can be configured to customer needs may add a competitive edge and improve customer satisfaction, but it can also lead to lower profits, increased costs, and strained engineering resources. For many manufacturers, the solution is modular product design. This webinar reviews the benefits of modular design - both for your customer and your internal organization. We also walk the viewer through important organizational challenges of implementing modular product architecture, which should be considered when deciding whether or not it is the solution for you.

Click here to register!



Two-Shot Silicon and Thermoplastic Molding:
The Innovative Cost Saving Solution for Medical OEM's

Sponsored by Saint-Gobain
DATE: April 2nd, 2008
TIME: 2:00pm ET/11am PT

Medical device designers are facing intense pressure to create innovative designs and maintain the highest quality over a product's lifecycle while also being forced to design for lower cost manufacturing. This is a challenge we recognize, but one that can be overcome by leveraging the cost savings and benefits of two-shot molding technology. Saint-Gobain's engineering team will present on two-shot molding, how this process innovation can provide cost savings, increased design freedom, and provide the quality and performance you demand.

Click here to register!



ARCHIVED WEBCASTS AVAILABLE FOR FREE VIEWING


Click Here for a list of archived Machine Design webcasts.

Featured Links

Zero-Max
The new CD couplings feature zero backlash precision and high torsional stiffness required in today's demanding servo motor applications with high reverse loads and positioning requirements. Newly improved CD couplings are designed with new clamp style hubs for increased torque capacity on shafts without using keyways.
Now you can select and configure the exact CD® coupling solution for your coupling application with 3D Partstream, the configurable 3D CAD downloads at www.zero-max.com

LEESON's new SM2 Vector Series inverters deliver up to 200% starting torque and control an Inverter rated motor down to 1Hz at full output torque.
www.leeson.com



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Contact Information
Editorial questions:   Julie Kalista 216-931-9458
Advertising/sponsorship opportunities:   Virginia Goulding 216-931-9893

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