Valve actuators

Abstract From the Canadian patent

OF DISCLOSURE. " Valve Actuators" A valve actuator comprises a variable speed motor a speed control circuit for controlling the motor speed including speed selector means by means of which the desired motor speed can be set to different values by adjustment means. A torque limit control circuit is arranged to stop said motor when a pre-set torque limit has been exceeded. The torque limit control includes a torque sensor arranged to provide a measure of torque from one or more torque-related electrical paramters of the motor for example a torque related current flowing in the motor, and adjustment means for setting torque limit control circuit to different torque limits.