Electricity: motor control systems – Open loop speed control system for dc motor with commutator – Analog armature control
Patent
1992-06-24
1997-05-13
Martin, David S.
Electricity: motor control systems
Open loop speed control system for dc motor with commutator
Analog armature control
318DIG2, 361 26, 361 32, H02P 7288
Patent
active
056300093
ABSTRACT:
A direct current (DC) electric motor is shifted between higher and lower operating speeds in response to motor operating conditions to prevent motor stalling, overheating and burnout. Switches are performed between two or among more than two operating curves defined for the DC motor with switches preferably taking place approximately at points of intersection of the operating curves. The high or higher speed curve typically results from inducing inefficiency into the motor such that continued operation along the high or higher speed curve can lead to motor stalling and even burnout. At or near the intersection points of motor operating curves, operation is switched from the high or higher speed operating curve to a lower speed, higher efficiency operating curve such that motor current is immediately reduced for the same motor speed and torque. If the motor is able to once again operate along the high or higher speed curve, a switch-back is made at or near the point of intersection. If more than two operating curves are provided for a DC motor, switches can be made from one curve to an adjacent curve. For more than two operating curves, switching is from the least efficient, to the next least efficient, etc. until operation of the motor is along the most efficient operating curve for the motor. Switch-backs are also effected as the energy dissipated in the motor is reduced, the load is reduced, etc. Preferably, some level of hysteresis is provided to prevent oscillation or hunting between two operating curves.
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Ford Motor Company
Martin David S.
May Roger L.
Sparschu Mark S.
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