Japanese Patent JPS6120237

B2

A stepping motor is driven with extended pulses producing an effective excitation intermediate to the single phase and the dual phase operations. The unique drive circuit creates a series of drive pulses for each motor phase so that each pulse slightly overlaps the drive pulse of the next adjacent phase. Thus, since each previous phase is still providing torque while the current in the next phase is being built up, the torque characteristics are improved, and the extended pulses are terminated before the subsequent phase is energized so that excessive power consumption is avoided. In closed loop systems, a fixed duration overlap provides the improved speed-torque characteristic at high speeds where the overlap is a large percentage of the drive pulse, while at lower speeds (such as when the motor is accelerating) where power consumption is greatest, the overlap is a smaller percentage of the drive pulse hence minimizing the increase in power consumption. This type of operation maximizes slew speed while conserving power consumption at low speeds. In open loop systems, using extended drive pulses increases the torque over that provided by single phase excitation, and the duration of the overlap may be adjusted so that large overlaps occur only where the torque needs are greatest (at times of acceleration, for example) while small overlaps occur where torque requirements are low (during constant speed operation, for example), thus minimizing the total overall power consumption.

REOHOORUDO FUON BURAUN

JP5999677A

May 21, 1986

May 25, 1977

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TELETYPE CORP

H02P8/22; H02P8/00; H02P25/08

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