In fact, the level gauge is not much different from the traditional float control. The level gauge is equivalent to several integrated floats. Familiar with float control, level control is naturally not difficult to master, so the following introduces the start and stop of the float control sewage pump. The sewage pump is generally driven by a three-phase AC motor, and its working requirements are:
1. When the water level of accumulated water and waste liquid on site reaches a high level, the drainage pump will automatically run to discharge the waste water;
2. When the water level drops to a low level, the drainage pump should be stopped in time to prevent the motor from being damaged by idling for a long time.
Based on the above working requirements, the start and stop of the motor must be completed automatically. The timing of its start and stop is controlled by the water level. A float switch can be used to achieve this function. A normally open contact is encapsulated in the float switch. When it floats, the normally open point is closed, otherwise it is open.
Since the motor is required to start when the liquid level is high and stop when the liquid level is low, a float is required to calibrate two liquid levels, high and low. The usual practice is to use two floats, one float is installed at a low liquid level, and the other is installed at a high liquid level.
The process is as follows:
1. When the water level is below the low level, the float switches -S01 and -S02 are in the off state, and the motor stops;
2. When the water level rises to between the low and high levels, -S01 is closed, -S02 is disconnected, and the motor still does not start;
3. When the water level rises to the high level, -S01 closes, -S02 closes, the contactor-K01 coil is energized and the motor starts to work; at the same time the normally open contacts (13,14) of the contactor-K01 are closed, Form self-locking;
4. When the water level drops again between the low level and the high level, -S01 is closed and -S02 is disconnected, but due to the existence of self-locking, the motor still keeps working;
5. After the water level drops below the low level, -S01 is disconnected, -S02 is disconnected, the contactor-K01 coil is de-energized and released, and the motor stops working;
6. The status of the indicator light is similar to manual start and stop, so I won't repeat it.
The control points of the sewage pump from start and stop:
A reasonable height difference between the high and low liquid levels should be maintained. If it is too large, it may cause poor drainage; if the drop is too small, the motor will frequently start and stop, which will affect the life of the motor.