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, generally after shutting down for one shift (8 hours), when starting the motor again, it is necessary to turn the machine.
In a hydrogenerator, there are multiple large shafts connected between the rotor and the runner, so it is necessary to manually rotate the rotor for one revolution, usually through a thrust bearing, in order to determine the unit's The deviation between the actual center and the theoretical center is adjusted based on the measurement data. If the deviation is not adjusted through axis extension, it will be amplified beyond the standard and affect the performance of the unit. It usually takes several turns to try to find the best center alignment.
1. There are two ways of turning: small units use manual turning, and medium-sized and large units use electric turning.
2. 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) .
2) Electric turning device with swing gear (used in domestic units of 50MW, 100MW and 200MW).
3. 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, and a spiral shaft. , turning gear, safety pin, handle, etc. 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.
4. The structure and working principle of the turning device with swing gear
The device mainly consists of gear set, swing shell, crank, connecting rod, handwheel, travel switch, spring, etc. composition. The gear set drives the rotor to rotate after two reductions.
When the turning device is disengaged, the swing shell is lifted by the lever system, and the swing gear is separated from the turning gear; the travel switch is disconnected, the motor does not rotate, and the tightening pin on the first wheel locks the handwheel in Disengaged position; the connecting rod pushes the crank tightly under the action of the compression spring, and the entire device cannot move.
When turning the car, pull out the locking pin, turn the handwheel counterclockwise, and the crank coaxial with the handwheel will rotate accordingly, overcome the thrust of the compression spring, and drive the connecting rod to move downward to the right; the pull rod It descends at the same time, causing the swing shell and the swing wheel to swing downward. When the swing wheel and the turning gear enter the meshing state, the travel switch is closed, the motor power is turned on, and the gear set starts to rotate. Since the rotor is still in a stationary state, the swing gear continues to swing clockwise with the swing shell until it is supported by the push rod. At this time, the swing shell is in the middle position, the swing wheel and the turning gear are fully meshed and begin to transmit torque, causing the rotor to rotate.
The automatic disengagement process of the turning device is as follows: after the rotor is driven, the rotation speed of the turning gear suddenly increases, and the swing gear changes from the driving wheel to the driven wheel, and is quickly pushed to the right with the swing. The shell swings counterclockwise, pushing the pull rod upward. When the upper end point of the tie rod exceeds the equilibrium position, the connecting rod pushes the crank to rotate counterclockwise under the push of the compression spring, pulling up the swing housing until the handwheel rotates through a predetermined angle, and the locking pin automatically falls into the lock hole and locks the handwheel. Locked. At this time, the travel switch operates, cuts off the power supply to the motor, all gears stop rotating, and the turning device returns to the disengaged state before it was put into use. Operating the cranking stop button and cutting off the power supply can also cause the cranking device to stop working.