Discussion at spring convention: Synchronous-motor drive for rubber mills

S. H. Mortensen: Mr. Drake's paper recognizes the importance of the application of dynamic braking to motors driving rubber mills and similar industrial installations where quick stops are necessary for safety reasons. The importance of this was brought to the speaker's attention in 1918, in connection with the design and operation of a 500-h. p., 450-rev. per min., self-starting synchronous motor, geared to a four-roll rubber-mill drive in the plant of the B. F. Goodrich Company in Akron, Ohio. This motor was installed for power-factor improvement and as it replaced a wound-rotor induction motor, it was connected to the mill by means of the magnetic clutch which formed part of the original motor drive, together with a solenoid-operated brake for stopping the mill in case of accident. As this installation was a novelty at that time, extensive tests were made on this motor. These proved not only its suitability for this type of drive but also that it did have ample starting torque to bring the mill up to speed with the clutch energized. Its pull-out was beyond any load that could be put upon it by overloading the mills with the toughest rubber available.