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Stepping Motor Bridge Drive

IP.com Disclosure Number: IPCOM000075687D
Original Publication Date: 1971-Oct-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Related People

Abraham, DG: AUTHOR [+2]

Abstract

A constant-current source seems to be the ideal driving means for a stepping motor, since more torque is made available than in the voltage drive case. Known drives use large-power supplies with large-series resistors in an attempt to reduce the L/R time constant and approximate a constant-current source. The present arrangement uses current already available to switch the next winding instead of using L/R buildup each time.

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Stepping Motor Bridge Drive

A constant-current source seems to be the ideal driving means for a stepping motor, since more torque is made available than in the voltage drive case. Known drives use large-power supplies with large-series resistors in an attempt to reduce the L/R time constant and approximate a constant-current source. The present arrangement uses current already available to switch the next winding instead of using L/R buildup each time.

Fig. 1 shows the connections required for this improved drive. Two of the windings, either N/S or E/W must have the current sense reversed from their normal orientation, as indicated by the polarity data. The flux vector shown in Fig. 2 is propagated in the following manner:

Initially, switches A and C are closed and B and D are open. This passes current through the N and E windings holding the rotor at NB. Step 1: A opens and B closes. No change in C and D. The current formerly flowing in A now flows in B. This current tends to remain nearly constant, because the same current is still flowing in the E winding. The flux is now at SE and the rotor is repositioned. Step 2: C opens and D closes with no change in A and B. Again, the current toggles to W, as explained above, with flux vector in the SW position. Step 3: B opens and A closes. Current toggles from S to N and the flux switches to NW. Step 4: D opens and C closes. Toggling current yields NE flux vector.

Resistor R is chosen to limit the maximum current. This...