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Extending the Speed Range for a Permanent Magnet Stepper Motor

IP.com Disclosure Number: IPCOM000060493D
Original Publication Date: 1986-Apr-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Nebgen, GB: AUTHOR [+2]

Abstract

An arrangement is described to operate a permanent magnet (PM) stepper motor efficiently over a wide speed range by alternating between unipolar and bipolar drive with only one drive circuit. A properly designed stepper system attains the highest possible energy efficiency by matching the motor inductance to the speed requirement such that no more current than necessary is driven through the motor windings. This usually implies low inductance windings driven at high currents to achieve high speed performance and higher inductance driven at lower currents for low speed. A motor designed for low speed is not usable for high speed because the inductance is too high to allow charging the windings at high speeds. The result is insufficient torque.

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Extending the Speed Range for a Permanent Magnet Stepper Motor

An arrangement is described to operate a permanent magnet (PM) stepper motor efficiently over a wide speed range by alternating between unipolar and bipolar drive with only one drive circuit. A properly designed stepper system attains the highest possible energy efficiency by matching the motor inductance to the speed requirement such that no more current than necessary is driven through the motor windings. This usually implies low inductance windings driven at high currents to achieve high speed performance and higher inductance driven at lower currents for low speed. A motor designed for low speed is not usable for high speed because the inductance is too high to allow charging the windings at high speeds. The result is insufficient torque. On the other hand, if a high speed motor is used at low speeds, it is typically not efficient because more current than necessary is required to achieve the required amp-turns with the low inductance motor. This arrangement addresses this problem to suit applications that require a wide range of speeds. One particular example of this type of application is a carriage drive for a unidirectional printer. Here the print speed is limited by the print technology, but the carrier return is fast, in an attempt to raise throughput to levels near those of bidirectional printers. The typical approach is to design the motor for the high speed and pay the price for power at the print speed. The result is a more costly power supply than required. In order to save power at low speeds (and consequen...