Robust asynchronous three-phase AC Motors are mostly used as the driving force, for some applications also single-phase AC or DC motors are used. These motors are specially adapted for valve automation as they provide higher torques from standstill than comparable conventional motors.
Often a worm gearing is used to reduce the high output speed of the electric motor. This enables a high reduction ratio within the gear stage, leading to a low efficiency which is desired for the actuators.
Valve attachment —
The valve attachment consists of two elements :-
First: The flange used to firmly connect the actuator to the counterpart on the valve side. The higher the torque to be transmitted, the larger the flange required.
Second: The output drive type used to transmit the torque or the thrust from the actuator to the valve shaft. Just like there is a multitude of valves there is also a multitude of valve attachments.
Manual operation —
In their basic version most T - Torque are equipped with a handwheel for operating the actuators during commissioning or power failure. The handwheel does not move during motor operation.
Actuator controls —
Both actuator signals and operation commands of the DCS are processed within the actuator controls. This task can in principle be assumed by external controls, e.g. a PLC. Modern actuators include integral controls which process signals locally without any delay. The controls also include the switchgear required to control the electric motor. This can either be reversing contactors or thyristors which, being an electric component, are not subject to mechanic wear. Controls use the switchgear to switch the electric motor on or off depending on the signals or commands present. Another task of the actuator controls is to provide the DCS with feedback signals, e.g. when reaching a valve end position.
Fieldbus connection —
Fieldbus technology is increasingly used for data transmission in process automation applications. T - Torque can therefore be equipped with all common fieldbus interfaces used in process automation. Special connections are required for the connection of fieldbus data cables.