The speed at which wind turbines spin can vary depending on the design and size of the turbine, as well as the wind speed conditions. Wind turbines are designed to operate within a specific range of wind speeds for optimal efficiency and safety.
Typically, wind turbines have a cut-in speed, which is the minimum wind speed required for the turbine to start generating power. This cut-in speed is typically around 7 to 10 mph (11 to 16 km/h). At this wind speed, the turbine begins to rotate and generate electricity.
The rotational speed of wind turbine blades usually increases with increasing wind speed up to a certain point. Most modern wind turbines have a rated or optimal wind speed at which they achieve their maximum power output. This rated wind speed is typically around 25 to 35 mph (40 to 56 km/h). At the rated wind speed, the turbine reaches its maximum rotational speed.
It's important to note that wind turbines have mechanisms, such as automatic control systems or aerodynamic braking, to prevent excessive rotation speeds and ensure safe operation during high wind conditions. These mechanisms are designed to protect the turbine from damage and maintain its structural integrity.
So, the specific speed of wind turbine rotation in miles per hour (mph) will depend on the wind speed at a given location and the characteristics of the turbine itself.