Omokawa – Francis unit with Electrical Actuators
This article aims at describing the special application of electrical actuators in the Francis turbine for the OMOKAWA Project. OMOKAWA is owned by Yamanashi Prefecture, government on Yashima Denki Co. Ltd. Tokyo, Japan.
The OMOKAWA HPP is equipped with one (1) unit of Francis machine running at synchronous speed of 750 rpm, operating under rated net head of 28.4 m. The unit can generate output of 110 kW. The powerhouse is situated at an elevation of 814.09 m above mean sea level.
Number of units: 01
Type of turbine: Horizontal Francis
Maximum Head: 29.9 m
Rated Head: 28.4 m
Rated turbine output: 110 kW
Synchornous speed: 750 rpm
Runaway speed: 1,280 rpm
Speed rise: 50%
Pressure rise: 23%
Definition of application of Electrical Actuators
Eliminate the use of grease lubrication is a technology adopted for more than thirty years in hydro equipment to maintain water quality. In the Kaplan runners, the concept of oil-free inside the hub is also applied but it is not so common since it demands successful experience from the manufacturer. Those two measures are to avoid direct contact or spill of oil into river water since they are related to components with direct interface oil-water.
Suppress the complete use of oil lubrication in hydro power plant is a trend. Although some components of the turbine that are driven by oil are not in direct contact and therefore there is no risk of direct contamination of the river water, the possible contamination of the areas around the main equipment and spillage of oil reserves constitutes a risk degradation of the environment to be avoided as much as possible. It can be observed more restrictive regulation following this trend in some countries.
In the OMOKAWA project, due to stringent quality standards set by our Japanese Customer based on regulation mandatory in this country, it was not allowed the servomotors for both turbine distributor as well as butterfly valve to be oil actuated. The requirement was the application of electrical actuators.
• Number of wicket gates: 20
• PCD of link bearing on regulating ring: 698 mm
The wicket gate actuator is of double acting type linear electrical actuator with planetary reducer & electrical servomotor. The actuator is mounted on spiral case on downstream side. The actuator rod is directly connected to gate operating ring and control the wicket gate position. The actuator is supplied with linear feedback signal to governor.
Power cylinder specifications (see Fig. 1 left)
• Product/series: Power Cylinder Eco Series servo type
• Allowable thrust: 1,500 N
• Motor mounting method: with precision planetary reducer
• Stroke: 120 mm
• Waterproof IP65
Diameter: 500 mm
PN: 3.5 bar
Motorized electric actuator with gear box drive. The actuator is mounted directly in the valve trunnion.
Motorized actuator specifications (see below)
• Product/series: IQ12 F10 B4
• Min. output torque: 2,350 Nm
• Indicator: limit switch for full open/close
• Gear box model: IW4R F16
• Waterproof IP68
Electric supply: 200 Vac, 3 phase, 50 hz.
Design of electric actuators
Next are show the pictures of actuators installed at site. On the left the distributor actuator direct connected to regulation ring arm and supported in the spiral casing support. On the right the motorized actuator in the butterfly valve directly mounted on the trunnion.
Observation and Conclusions
After the commissioning of machines in the OMOKAWA HPP on May 2017, the design validation was done based on the observation that:
- The selected actuators types are proven to be the proper choice.
- Integration with electronic governor is flawless.
- The environmentally friendly features of actuators applied in this project are helping in its sustainability as expected by Customer.
- This application is part of FLOVEL technology under the environment friendly care concept.
FLOVEL name has been synonymous with the hydro power sector for over four decades. FLOVEL is a full-line supplier of electromechanical equipment and services for small and medium size hydro power plants manufacturer of hydraulic turbines, valves and turnkey supplier of electro mechanical packages for hydro power projects and ranks amongst the leading players globally. FLOVEL manufacturers complete range of Pelton, Francis, Kaplan, Axial Flow turbines and Valves for hydropower projects. The strength of FLOVEL is in its ability to offer all-inclusive solutions (Electro Mechanical-Turnkey Packages).