How do designers know about kilowatt power of wind turbine generators like 1.5 MW?
Generators are designed for a specified capacity that includes both a kVA and a kW capacity. Wind turbines are designed for a specified capacity to drive a turbine that would include the torque that can be provided at a given speed over a specified range of wind speeds and rotating speeds. What is known is the power that can be delivered at any wind speed. A generator of a given capacity will not be installed unless there is a reasonable expectation that there is sufficient demand for power to make the installation economically advantageous.