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Connection Smoothes Mid-Speed Steppers

Connection Smoothes Mid-Speed Steppers


Connection to A T: With an architecture between series and parallel connectorion, the T-Connection serves mid-speed stepper motor applications and minimizes noise and vibration. Smoothness comes from tailoring flux generation between and within coils.

This patented stepper motor connection architecture looks to smooth operation of these motors for mid-range speed applications of approximately 5 to 10 rps. Sales director and engineer Ryan Lin notes that motors wired with stator coils in series provide higher inductance and work best for uses at low speeds. A motor wired with the coils in parallel reduces reluctance, which facilitates high-speed running. The T-Connection has twice the reluctance of parallel coil connections and half that of series connections, and thus performs in the speed range where neither the parallel nor series can run efficiently, notes Lin.

"A customer came to us and was insistent on wanting smooth, efficient operation at these speeds," Lin mentions. Company engineers had to think of something not thought of before, he says. With the T-Connection, the inductance is optimized in the mid-range. Here the coils are connected in series between phases (see diagram), which tailors the electromagnetic flux generation and path of dynamic torque within and between coils to damp out system resonances. The result: smoother, quieter operation at the speeds needed.

Lin also notes that a stepper motor drive first energizes one phase and then two phases. This sequence sometimes results in jerkiness. "But with the T-connection there are always two phase positions energized, whether with one or two coils, which gives smoothness." With higher resistance of two coils in series but low inductance, Lin adds, "The T-Connection has a low L/R time constant, good for a voltage drive, which requires a certain resistance to control the current, and it is also good for applications that require low current input."

T-Connection steppers have been used in applications such as printing large banners where uniform dot-to-dot separation is needed for reproducing high-resolution images cleanly. They have also served to position Earth satellite antennas and for controlling medical sampling carousels.

Lin Engineering www.linengineering.com Enter 585

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