The so-called "turning" refers to turning the motor several times manually before starting the motor to determine whether the load driven by the motor (ie, the mechanical or transmission part) is stuck and the resistance increases. situation, so that the starting load of the motor will not increase and the motor will be damaged (that is, burned out).
Therefore, it is generally necessary to crank the motor when starting the motor again after shutting down for one shift (8 hours).
There are two main forms of electric turning devices:
1) Electric turning devices with screw shafts (used by most domestic small and medium-sized steam turbines and 125 and 300MW units)
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2) Electric turning device with swing gear (used in domestic units of 50MW, 100MW and 200MW)
4. It has a spiral shaft electric turning device and working principle
The spiral shaft electric turning device consists of a motor, a coupling, a small gear, a large gear, a meshing gear, a spiral shaft, a turning gear, a safety pin, and a handle. etc. composition. The inner surface of the meshing gear is milled with helical teeth that mesh with the helical axis. The meshing gear can slide left and right along the helical axis.
When it is necessary to put the cranking into operation, first pull out the safety pin, push the handle, and turn the motor coupling until the meshing gear and the cranking gear are fully meshed. When the handle is pushed to the working position, the contact of the travel switch is closed and the cranking power is turned on. After the motor starts to full speed, it drives the turbine rotor to rotate for cranking.
When the steam turbine starts to rotate and the rotor speed is higher than the turning speed, the meshing gear changes from the original driving wheel to the passive wheel, that is, the turning gear drives the meshing gear to rotate, and the axis of the spiral shaft When the direction of the force is changed, the meshing gear and the screw shaft rotate relative to each other, and move along the screw shaft to exit the meshing position. The handle then rotates in the opposite direction to the deactivated position, disconnects the travel switch, and the motor stops rotating and basically stops working.
If you need to stop cranking manually, you can press the cranking motor stop button, the motor will stop, the meshing gear will exit, and the cranking will stop.