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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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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
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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
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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
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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.
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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.
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UPCOMING IN-PERSON EVENTS
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Click Here for a list of archived Machine Design
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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
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216-931-9893
Machine Design
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