Control Engineering Motors, Drives, & Motion Control Newsletter for February 2001

By Frank Bartos June 4, 2002

In this issue:

  • A ‘magnetic’ alternative to variable-speed control
  • Transmit torque through barrier
  • Free linear motor design software
  • Medium-voltage ac drives update
  • Direct machining initiative incorporates soft motion
  • Motor briefs
  • Companies in motion
  • Control Engineering in February
  • Wanted: Users’ input on energy efficient motors
  • Take a survey on support and service

A ‘magnetic’ alternative to variable-speed control

Are you looking for an alternative to variable-frequency drives for speed control of ac motors up to 600 hp in your pump, fan, or blower applications? If so, MagnaDrive Corp. (Seattle, Wa.) has another choice based on a magnetic coupling principle. No, it’s not a version of eddy-current control.

Named MagnaDrive Coupling, the device is placed between the motor and its driven load. The ‘coupling’ has two main non-contacting members-a copper conductor assembly connected directly to the motor (input) shaft and a precision rotor assembly, containing rare-earth neodymium-iron-boron (N-Fe-B) magnets, connected to the load (output) shaft. Relative motion between the high-energy N-Fe-B magnets and copper conductors develops a magnetic field that transmits torque through the air gap between the independent members. A linear actuator responding to 4-20 mA process signals adjusts the torque magnitude by varying the air gap width. This changes the coupling force, although the motor and load are not connected mechanically.

MagnaDrive Coupling offers benefits beyond energy savings typical to all variable-speed controls. It eliminates harmonics, coupling-induced vibration, and the need for drive cabinet space; is insensitive to power quality; and provides ‘soft’ start and stop control. Reduced equipment and maintenance costs are the results, says the company. The device works with low-voltage (460 V) as well as medium-voltage (4,300 V) motors. Contact MagnaDrive for more information at Tel: 206/336-5710 or

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Transmit torque through barrier

In a loosely related item, Rimtec Corp. (Addison, Ill.) offers new magnetic synchronous torque-limiting clutches that transmit torque through a housing, cabinet, or other sealed application. Two disks (or cylinders), lined with permanent magnets, face each other across the barrier and an air gap. The manufacturer claims ‘servo-quality’ torque is produced, as one disk or cylinder rotates relative to the other. Disk-type MDC clutches produce 17-256 lb-in. torque, with 0.125-1.14 in. OD shafts. Cylinder-type MSV clutches (where the smaller cylindrical element rotates inside the larger one without touching) offer 440-8,850 lb-in. torque, with 0.75-2.5 in. shafts. Nominal air gap is 0.25 in. for the above ratings.

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Free linear motor design software

Linear motors can add more options to your toolbox of solutions. Free software is available to help select linear motors and servo controllers made by LinMot , a division of NTI Inc. of Switzerland. (The company’s U.S. office is located in Rogers, Minn.) ‘LinDesign’ simulates the action of LinMot linear motors under static and dynamic loading. The software lets users design the overall system, without time-consuming calculations of motor details. Ability to quickly validate design alternatives is a further benefit. To obtain LinDesign, call 877/546-3270.

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Medium-voltage ac drives update

New developments in large medium-voltage (MV) ac drives continue to bring their more efficient operation at higher voltages and other ‘economies of scale’ to wider applications. Here are a few examples.

Advanced Cell Bypass (ACB) technology from Robicon Inc. (New Kensington, Pa.) now makes its 3rdgeneration Perfect Harmony MV drives more reliable. In case of a power module failure, ACB technology bypasses the disabled cell to minimize the drop in drive voltage or speed. For a nine-module (three-phase) drive with one failed module, Robicon cites 83% voltage capability and 93% speed remaining when using ACB. The same drive without ACB would produce only 67% voltage and 85% speed. A patented ‘Neutral-Shift’ method within Advanced Cell Bypass technology is said to also prevent unbalanced voltages between the drive’s phases, which limited earlier cell bypass designs.

Alstom Power Conversion (Pittsburgh, Pa.) added an air-cooled version to its Symphony family of MV drives. Developed by Alstom in Germany for use in the Americas and manufactured in the U.S., these units have a power range of 500-3,000 hp. Symphony drive’s multi-level control topology uses a lower number of medium-voltage IGBT (insulated-gate bipolar transistor) power-switching devices. Typical overall drive efficiency (including input transformer) is reported to be over 96.5%. Expected availability of the drive is April 2001.

Since its introduction in late 1999, Allen-Bradley PowerFlex 7000 MV drive from Rockwell Automation Canada Inc. (Cambridge, Ont., Canada) has experienced twice the number of sales anticipated, according to Ralph Paling, manager of marketing communications. Orders have come from 12 countries worldwide. One reason for customers’ positive acceptance has been the shorter than expected commissioning time for these drives, explains Mr. Paling. PowerFlex 7000 air-cooled MV drives are available in standard supply voltages from 2,400 to 6,600 V to control induction and synchronous motors ranging from 500 to 4,000 hp.

Long-term availability tests are ongoing on the submersible version of ACS 1000 MV drive, developed by ABB Industrie AG (Turgi, Switzerland) and ABB Industri AS (Oslo, Norway). ACS1000 for the Subsea Electrical Power Distribution Systems (SEPDIS) project will be installed on the seabed more than a mile deep to directly power motor-driven pumps and compressors for more efficient offshore oil and gas production. Commercial availability is expected in a year. For more detail on this submersible medium-voltage drive and the SEPDIS project, see CE , Nov. 2000, pp 8, 10 .

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Direct machining initiative incorporates soft motion

DMAC (Direct Machining And Control) research group, part of the Department of Mechanical Engineering at Brigham Young University (Provo, Ut.), has launched an advanced machining initiative to simplify manufacturing processes. DMAC methods promise to drive production machines and robots directly from CAD models and their associated feature attributes. Direct machining integrates the part description software and machine controller on the same PC, eliminating numerous intermediate post-processing and control steps, according to the research group. In particular, proprietary servo cards, conventional controllers, and APT, CL and M&G code programming will be eliminated. Motion objects and soft motion techniques are incorporated in DMAC.

A consortium of companies to support DMAC is forming. The consortium seeks membership of major companies with expertise in CAD/CAM, machinery building, digital drives, robotics, and tooling, as well as national or governmental organizations and end-users. Two initial developments involve five-axis machining systems-a friction stir welding (FSW) machine for joining large surfaces, and a parametric and curvature matched machining application integrated into the machine tool controller.

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Motor briefs

Rockwell Automation (Mequon, Wis.) just announced its Allen-Bradley MP-Series brushless servo motors with high efficiency, torque, and package density features. Initial range of torque ratings is 1.6-10.2 Nm (14.2-90.3 lb-in.). Several feedback options are offered, such as absolute positioning and high-resolution encoders (coming in mid-2001).

Also new from Industrial Devices Corp. (Petaluma, Calif.) are BN Series brushless servo motors in NEMA 23 and 34 frame sizes. These smaller motors supply 4.38-35 lb-in. peak torque. Top speed is 6,000 rpm.

Thomson Airpax Mechatronics (Chesire, Conn.) has introduced a thin-profile permanent magnet stepper motor series, measuring 44-mm diameter by 12-mm long (1.7 in. x 0.48 in.). Bipolar Series 44M100D produces 100 steps per revolution (3.6° step angle) and handles 2 W input power per winding. Pricing is under $10 each in lots of 500.

Need something smaller in motors? A line of 12-mm (less than 0.5 in.) diameter motors that supplies up to 1.3 W power is available from MicroMo Electronics Inc. (Clearwater, Fla.). Series 1224 dc coreless motors come in 6, 12, or 15 V dc versions and produce stall torques up to 0.52 oz-in. Spur and planetary gear heads raise maximum output torque to 63.7 oz-in. The magnetic encoder series integrates two-channel TTL level output into the same 12-mm OD body, to provide either 10 or 12 counts per revolution.

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Companies in motion

Manufacturing Data Systems Inc. (MDSI, Ann Arbor, Mich.) moves into the general motion control market with the introduction of WinMotion software, built on the same core technology as its basic OpenCNC software CNC product. WinMotion is designed to provide soft motion control, a soft PLC (IEC 61131-3), and a data server in one software application. There is no need for any motion control card or proprietary hardware. MDSI will demonstrate the new software at National Manufacturing Week (NMW) in Chicago, during March 5-8, in booth 5537.

In a related item, MDSI and AutomationSolutions (ASI, Petaluma, Calif.)-an automation solutions provider with a nationwide sales and support organization-have signed a strategic partnership agreement for marketing and integrating MDSI’s WinMotion software general motion control products within the U.S.

Danaher Corp. (Washington, D.C.) announced February 20 the formation of ‘Danaher Motion’ group, combining several motion control companies it has acquired over the past two years. Danaher Motion consists of API Motion, Inmotion Technologies (formerly known as Atlas Copco Controls), Kollmorgen, Superior Electric, Warner Motion, and Pacific Scientific. The new entity, organized into four business groups, will make its debut at National Manufacturing Week in Chicago. See more in Feb. 20, 2001 Daily News .

On January 29, Yaskawa Electric America Inc. (YEA, Waukegan, Ill.) acquired MagneTek Inc.’s (New Berlin, Wis.) drive products business. This business unit sells, modifies, and services general-purpose and high-performance ac drives, and was a part of MagneTek Drives & Systems group.

Nanomotion Inc. (Santa Clara, Calif.), a specialist in miniature Piezo Ceramic Motors, has signed an agreement with Botec Corp. (Smithtown, N.Y.) for business development collaboration in the photonics, semiconductor, and general automation markets. Botec will promote Nanomotion products throughout the eastern U.S. It offers a full range of services, ranging from design review and quotation to prototype design and after-sales support for Nanomotion’s equipment. Seminars and demonstrations are also conducted at qualified customer sites. For Botec, contact .

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Control Engineering in February

More detail on Yaskawa’s purchase of MagneTek’s business unit appears in the Up Front department.

Coverage of the Electric Automation show, SPS/IPC/Drives 2000 in Nurnberg, Germany (Nov 28-30, 2000) follows in the news section. It includes developments and items of interest to motors, drives, and motion control practitioners. A longer version can be found in January 29, 2001 Daily News .

In our preview article of NMW and National Industrial Automation Show (Chicago, March 5-8), Baldor Electric’s (Fort Smith, Ark.) wide line of motors and controls, and Danaher Control’s (Gurnee, Ill.) incremental encoders are among products to be exhibited. A more prominent Motion Hall is promised by the organizers for this year’s NMW show.

The products section features Accelerator architecture chip sets from International Rectifier Corp. (El Segundo, Calif.) that improve the design of motor controls through a ‘power management’ approach. Lynn Electronics Corp.’s (Charlotte, N.C.) innovative optical encoder testing/monitoring tool (p. 114) will appear in total in the March issue. In the meantime you can see an expanded online version in Jan. 19, 2001 Daily News .

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Wanted: Users’ input on energy efficient motors

In the May issue of Control Engineering, I will be doing an article on ‘Energy Efficient Motors’ and their related issues. Users’ experiences with energy efficient and ‘premium efficiency’ ac induction motors are needed. No motor suppliers please. Send me your views in brief form. E-mail:

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Take a support/service survey

What are your experiences with post-sale support and service in your product or regional area? Please invest a few minutes of your time to give us feedback by taking a survey on control and automation service support. Participants will be entered in a drawing to win one of five $200 e-gift certificates. Results will be reported in the June 2001 issue.

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