Method for determining an efficiency and/or for calibrating a torque of a drivetrain, in particular of a wind turbine

A method for calibrating a torque measurement of a drivetrain of a wind turbine, on a test rig, wherein the drivetrain has a motor-side end on a main shaft connectable to a motor and a generator-side end, between which ends a generator is arranged, the method comprising:

• performing a first test, wherein in the first test, the motor-side end of the drivetrain is driven and a variable dependent on a main shaft torque is determined at the motor-side end of the drivetrain and an electrical power Pelec is determined at the generator-side end of the drivetrain;
• performing a second test, wherein in the second test, the generator-side end of the drivetrain is driven, and the variable dependent on the main shaft torque is likewise determined at the motor-side end and the electrical power Pelec is determined at the generator-side end;
• and
• determining calibration parameters a and b from the electrical power values Pelec and the variables dependent on the main shaft torque determined in the first test and in the second test, using at least one predetermined assumption, wherein the first and the second test are carried out for at least two torque settings.