High performance electromechanical steam turbine actuator

Steam turbine electromechanical actuators deliver increased performance, safety and stability compared to traditional solutions and the Diakont technology also provides dual redundancy and failsafe features.

These EMAs are based on precision machined roller screws which are integrated with high-performance permanent magnet synchronous motors (PMSM) and electromagnetic clutches to form a single compact unit. Mechanical failsafe is provided by powerful closure springs and redundancy is created by dual parallel control channels.

The roller is positionable to within 0.01mm or 0.0004”, which means steam pressure can be precisely maintained, thus improving the turbine’s power performance compared to hydraulic and pneumatic actuation systems. The thread geometry ensures a large contact area compared to ballscrew actuators, ensuring a long and reliable working life (100,000hrs MTBF), and higher load force capacity.

INMOCO’s Gerard Bush noted that roller actuators have reduced maintenance and repair requirements compared to hydraulic units: “All the critical mechanisms of the Diakont actuators are environmentally sealed, so protected from abrasive particles and corrosive contaminants.

“Diakont EMAs are already popular overseas and have been proven to reduce the steady state tracking error of steam generator pressure from roughly 8.7psi to 1.5psi, allowing electrical power output to be increased by around 0.2%, a substantial performance gain over the life to the unit. Further, they can complete a full linear stroke in less than 50ms which increases turbine safety and overspeed protection.”