Magnetek, Inc.

Bryan Radke

John Backman

Marcus Adams

John A Backman

A system and method for detecting a brake dragging during normal operation of a motor monitors torque at zero speed and at constant speed. For an inertial system acted upon by gravity, a value of torque required to maintain zero speed is approximately the same as a value of torque required to maintain operation at a constant speed. In an exemplary, elevator system, a motor drive determines the torque required to maintain zero speed operation of an elevator cab after a holding brake opens and before it begins controlling the motor to rotate. The motor drive again determines the torque required to maintain a constant speed and compares this value to the value of torque required to maintain zero speed. If the difference between the two values of torque is greater than a predefined threshold, then the motor drive determines that the brake is dragging and sets an error message.

System and method of detecting a dragging brake in an elevator application

A motor drive receives a position feedback signal from an encoder operatively connected to a motor. The motor drive executes multiple position determination modules to determine multiple approximate motor shaft positions. On each iteration of a position determination module, the motor drive samples the feedback signal, increments a pulse counter when a new encoder pulse is received, adds the pulse counter to a high-resolution pulse counter register, and calculates an approximate motor position as a function of the value of the high-resolution pulse count register. The motor drive averages the multiple approximate positions, and the result is used by a speed regulator module executed on the same motor drive to achieve the desired operation of the motor. The speed regulator iterates at a slower rate than any of the multiple position determination modules.

System and method of increasing resolution of position feedback for motor control

A motor drive receives a position feedback signal from an encoder operatively connected to the motor. The motor drive executes a speed regulator module on a first periodic interval to achieve desired operation of the motor, and the motor drive executes an additional module at a second periodic interval, occurring more frequently than the first periodic interval, to increase the resolution of the position feedback. The position feedback signal is provided as or converted to counts. The motor drive maintains a first counter with a running total of each count received as well as a second counter which generates a higher resolution value than the first counter. During each second periodic interval the motor drive increments the high-resolution counter by the number of actual counts detected within the corresponding first periodic interval. This high-resolution counter is used by the speed regulator to obtain desired operation of the motor.

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West Allis, WI, United States of America

Bryan Radke