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Step Motor Drive Circuit

IP.com Disclosure Number: IPCOM000085639D
Original Publication Date: 1976-May-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Pawletko, JP: AUTHOR

Abstract

The use of cross-coupling capacitors 1 for a three-phase variable reluctance motor with bifilar windings A-F, such as that shown schematically in the figure, results in several benefits:. a) Capacitors 1 provide for the intermediate store of inductive energy, resulting in a higher winding current than that of the supply current. b) No zener or clamping networks are required because of the cross coupling in a network, i.e., when winding A is turned off, and winging C is turned on, a clamp to ground is provided so that the peak collector voltage can then be determined by the L/C ratio, thus controlling the inductive spike. c) Because the harmonic content of the current waveform has been reduced, lower eddy-current losses and magnetorestriction noise are achieved.

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Step Motor Drive Circuit

The use of cross-coupling capacitors 1 for a three-phase variable reluctance motor with bifilar windings A-F, such as that shown schematically in the figure, results in several benefits:.
a) Capacitors 1 provide for the intermediate store of inductive

energy,

resulting in a higher winding current than that of the supply

current.
b) No zener or clamping networks are required because of the

cross

coupling in a network, i.e., when winding A is turned off, and

winging C is turned on, a clamp to ground is provided so that

the peak

collector voltage can then be determined by the L/C ratio, thus

controlling the inductive spike.
c) Because the harmonic content of the current waveform has been

reduced,

lower eddy-current losses and magnetorestriction noise are achieved.
d) By placing diodes 2A-2F across respective switches 3A-3F, which may

be transistors, better damping and current rise times can be

achieved

while protecting the transistors from reverse bias.

The insertion of two blocking diodes 4 in series with the common supply circuits for the windings ACE and BDF also adds the following benefits:
a) The winding nodes are fully isolated thereby reducing phase

interaction.
b) The diodes allow the inductive and back EMF voltages to reach

full values without dissipation in the series resistors 5,

thus developing higher decelerating phase currents.
c) Power supply current is reduced by using the stored energy in

the coil inductance.

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