Rotary limit switches are used in wind turbines for managing and controlling the position of the nacelle (yaw control) and in some cases for pitch angle of the blades (pitch control).
Whenever the direction of the wind changes, the wind turbine nacelle will adjust accordingly to face perpendicular to the wind. Therefore, if the wind turbine nacelle rotates in the same direction for an extended period, the cables inside that carry the power from the generator down to the tower will become dangerously twisted. This is where the rotary limit switch comes in, in simple terms it acts as a ‘detangler’ to ensure the cables don’t become twisted as the direction of the nacelle changes.
Rotary limit switches may be the good old conventional geared limit switches with rotary encoders referred to as yaw switches, or sometimes simply called “yellow boxes.”
Alternatively, now available are modern electronic versions where the mechanical limit switches are replaced with programmable “softcams.” These newer versions are 100% maintenance free and offer more flexibility and a significantly longer lifetime. With the softcams (relays) the hysteresis becomes near to 0, because there are no mechanical movements in the microswitches.
Whatever the preferred technology for the specific wind turbine, the rotary limit switches shall offer the capability to monitor the position of the nacelle and precisely manage the yaw drive to stop the rotary motion of wind turbine safely, for anti-twist protection of the power cable.
Wind turbines operate in difficult thermal conditions with great thermal shifts between night and day, and they are subject to a variety of weather conditions such as water, dust, UV rays and brine. Therefore, for the rotary limit switches to have long electrical durability, accuracy of control and maintain resistance to extreme temperatures, it is essential that they have a high degree of protection against all possibly external interference.
TER has acquired decades of experience in designing and manufacturing rotary limit switches, providing a complete range from the conventional geared limit switched to the high fashion types offering the flexibility of programming, long lifetime and maintenance free operation. Wind Cluster offers the complete range of products from TER.
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