Application of Time Servo System in Construction Elevator Project
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The construction elevator of this project is a construction crane with gear rack and pinion. It is mainly used for the transportation of personnel and materials in the construction of high-rise buildings, bridges, chimneys and other high-rise structures. It can also be used as a warehouse dock and other places as a vertical transportation equipment. Use. The model to be retrofitted is SCD200/200, and its main electrical performance parameters are as follows:
The key part of the lift determines the performance of the whole machine. Before the transformation, the control mode of the ordinary elevator is realized by the contactor control: when starting, the motor is started while the brake disc is released; when stopping, the brake is held when the motor is de-energized. The result is a single speed, a large braking shock, serious damage to the structure and mechanism, electrical components are also vulnerable, and the operating speed is relatively low. If the speed is simply increased, the acceleration will be too large, and the impact of the structure and mechanism will be too large to accelerate the wear of the rack and the brake disc, thereby reducing the reliability of the operation. At the same time, due to the synchronous dragging of two motors (as shown in Figure 1), when the speeds of the two motors are inconsistent, damage to the reducer, mechanism, etc. is caused.
(1) gear (2) guide wheel (3) reducer (4) reducer bottom plate (5) cone drum speed limiter (6) speed limiter bottom plate (7) coupling (8) motor
2, the solution
For the application requirements of the construction elevator, redesigned on the basis of the IMS series servo controller, two 7.5kW are installed in one control box, sharing a rectifier bridge instead of the original contactor, through the control panel (see Figure 2) The control servo controller drives two 11kW motors to drive the cage up and down.
The initial scheme was controlled synchronously by two motors. The experimental results showed that the power output of the master controller was small due to the rigid connection of the two motors, and the output of the slave controller was small. Later, two motors were fed back through the encoder to realize separate closed-loop control of speed and current. Under the different loads, the speeds of the two motors were exactly the same. Damage to some mechanisms such as the reducer due to the inconsistent speed of the two motors is avoided. At the same time, the start and stop of the lift adopts acceleration control. When starting, first power on the motor, lock the motor at 0 speed, then release the brake, the motor starts to accelerate to the running speed according to a certain acceleration curve. When stopped, the motor decelerates from high speed to 0 speed, the brake is closed, and the motor is powered off. It avoids the impact on the rack and pinion when starting the brake when the contactor is controlled, and improves the stability and comfort during the operation of the construction elevator.
3. Project implementation effect
The two motors are controlled by closed-loop control. The difference between the two motors is small and there is basically no error. This overcomes the toothing phenomenon caused by the inconsistent speeds of the two motors when the contactor control is used. Compared with the lift before the transformation, it has the following characteristics:
(1) The starting and braking are stable and there is no impact. Compared with the general elevator, it overcomes the uncomfortable feeling when starting and braking.
(2) The lifting speed is easy to adjust, and the running speed can be changed at will.
(3) The starting current is less than the rated current. The starting current of an ordinary construction elevator is about 4-5 times of the rated current, and the requirements for the power supply and the power supply cable are high. The high-speed construction elevator has strong applicability to the power supply.
(4) The mechanical wear is reduced, and since there is no impact at the time of starting, the mechanical wear of the gears, racks, and the like can be greatly reduced, and the wear of the brakes is extremely reduced.
(5) Energy conservation is obvious. Especially compared with hydraulic lifts, the effect is more obvious.