MOTION SYSTEM TRENDS
The new motor breeds: Smart, connected, compact
These Unimotor hd brushless ac servomotors from Control Techniques, a Nidec Motor Corporation business, are low-inertia pulse-duty servomotors that accept 230-V or 460-V input; are capable of 6.3 to 757.6 lb-in. output (to 2,257 lb-in. peak); and come in frame sizes of 55 to 190 mm. These motors have a torque profile matched to Digitax HD servo drives for up to 300% peak overload for peak dynamic performance. The Unimotor hd servomotors excel in dynamic flying shear; pick and place; and cut-tolength applications requiring hard accelerations and decelerations.
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his year’s survey of trends in electric motors for motion control and automation revealed several trends and emerging developments in the use of synchronous ac motors; stepper motors, especially in closed-loop offerings; brushless motors of various types; and a smattering of specialty direct-drive offerings just making inroads. PROLIFERATION OF SYNCHRONOUS AC MOTORS With construction and operation much like those of brushless dc (bldc) motors, synchronous ac motors — sometimes billed brushless ac, permanent-magnet (PM) ac motors, and even PMACs — are now spreading from sophisticated servomotor applications into other industrial-drive applications. More specifically, they’re seeing increased use on printing and packaging equipment; conveyors; vehicle hub drives (which we'll explore in an article on AGVs and robotics in the special motion issue of Design World coming in May); hoists and cranes; and regenerative elevator drives.
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These lightweight low-inertia motors typically deliver 5 to 150 hp at high torque and efficiency. Case in point: Sinochron PMAC motors from ABM Drives maintain efficiencies 10 to 15% better than comparable induction motors. Synchronous ac motors’ variable-speed operation necessitates control via an inverter or VFD specially designed to start and synchronize the rotor-stator interaction. Just as bldc motors, synchronous ac motors use electronics (typically Hall-effect sensors) to dictate the correct amount of current to the windings. Arrays of four or more permanent magnets on the rotor make for synchronous operation. But unlike bldc motors with trapezoidally wound stator coils (and back-EMF output with trapezoidal waveform needing direct current input) synchronous ac motors are wound sinusoidally. That makes for sinusoidal back-EMF output (and the need for sinusoidal current input) as well as an audibly and electrically quieter motor. Visit motioncontroltips.com and search, “difference between motioncontroltips.com | designworldonline.com
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