Speed controller for mill drives and the like

Speed control apparatus for a drive motor having an armature and a field winding and having a base motor speed when the field winding has full rated current, and having a power supply and a power source to provide current to said field winding and said armature respectively, said apparatus having a first control portion having a first speed of response to control motor speed during normal running and a second control portion having a second faster speed of response to adjust the control of motor speed during abrupt changes of load torque to compensate for the changes, said first control portion comprising

• a sensor for sensing actual motor speed and providing a signal representing actual motor speed,
• a first adder for receiving a speed reference input signal and from said sensor a signal representing actual motor speed and providing a first signal related to the difference,
• circuitry for receiving said first signal and responsive to said field current being below said rated current modifying said first signal by a factor inversely proportional to the flux provided by said field,
• first integrating means for receiving from said circuitry for receiving said first signal a modified first signal, integrating said first modified signal and providing a current reference signal related thereto,
• a second adder for receiving from said integrating means said current reference signal and from said power source a signal representing actual current to said armature and providing a second signal related to the difference,
• control means for said power source for receiving said second signal and responsive thereto for adjusting the current provided by said power source to cause said motor to run at a speed related to said speed reference input signal,
• said second control portion comprising
• non-linear circuit means for receiving a signal representing field current and providing a third signal related thereto and representing flux,
• multiplier means for receiving said current reference signal and said third signal to provide a signal representing a model value of developed torque,
• a third adder for receiving said signal representing said model value of developed torque and a signal representing a model value of load torque and providing a fourth signal related to the difference and representing a model value of a net torque available for acceleration,
• second integrating means for receiving said fourth signal, integrating said fourth signal and providing a signal representing model motor speed,
• a fourth adder for receiving from said second integrating means said signal representing model motor speed and from said sensor a signal representing actual motor speed and providing a fifth signal related to the difference,
• third integrating means for receiving said fifth signal, integrating said fifth signal, and providing said signal representing said model value of load torque,
• differentiating means for receiving said signal representing said model value of load torque, differentiating said signal and providing a sixth signal representing a compensating speed adjustment, and
• means for applying said sixth signal to said first adder to adjust said first signal to compensate more rapidly for changes due to load torque.