M.E.A. Incorporated manufactures an Electric Rotary Actuator designed to rotate the steam admission valve cam shaft on large driven turbines.The actuator rotation can be as much as 300 degrees and full rotation can be achieved in as little as two seconds. The output torque is 6000 lbs. per inch at full speed. The actuator positions the output shaft proportionally to a 4-20 mA input control signal. The positioning accuracy is better than 1%. The Actuator operates from a 3 phase AC (Alternating Current) line. The actuator can be provided with a back-up manual driven by either a DC (Direct Current) motor or a pneumatic motor.
- A high performance servo motor is used to drive the actuator. Maximum servo motor speed is 4000 RPM (revolutions per minute).
- This servo motor is coupled to the input of a 160/1 harmonic drive speed reducer. The speed reducer output shaft can rotate at 25 RPM or 0.417 RPS (revolutions per second). The motor torque is increased 160 times.
- The harmonic drive speed reducer is a single reduction device. It operates at 90% efficiency and is virtually backlash free. Any inertia of the load (cam shaft) is reduced by 15,600 allowing exceptional response to input changes. The output shaft drives a precision rotary position transducer. This transducer provides the position feedback signal.
- The rotary shaft also carries to actuate end of travel limit switches. If an emergency drive (DC motor or pneumatic motor) is provided, it is coupled to the servo drive by a timing belt. The timing belt drives a clutch added to the main drive shaft between the speed reducer and the servo motor.