Water pump soft start principle Water pump soft start circuit diagram

Water pump soft start principle

Water pump soft start refers to a soft starter that specifically controls the slowness and speed of the motor.

Water pump soft start means that when starting the water pump, a certain method is used to make the starting current of the water pump motor the same as the rated current to avoid damage to the equipment and the power grid caused by high current starting.

When the pump outlet valve is closed, the pump inlet valve is opened, and the water pump is ensured to be "self-priming" (the liquid level is higher than the pump inlet pipeline condition, the starting procedure of the water pump is: start the motor, and when the motor is operating normally, slowly open the outlet valve to slowly increase the water flow. However, when there is no operation (opening the valve), the pump is automatically started, and the pipe diameter and length are large (the water mass in the pipe will be large). If the motor starts quickly, it will quickly push the large mass of water to accelerate (just like a train needs to accelerate quickly), which will make the motor start current very large, causing the motor to trip and damage the machinery and motor. The above situation can be overcome by using soft start (adding a soft starter to the circuit) - that is, the motor slowly increases the speed.

When starting directly, the current may reach 6-7 times the rated current, which will cause problems for other electrical equipment in the factory. When using soft start, the starting current is about 2-3 times the rated current. For water pumps, there is also soft stop, which allows the water to slowly fall back and eliminate the water hammer effect. Simply put, it starts slowly and stops slowly. This slow time can be adjusted, about 1-60 seconds.

Water pump soft start circuit diagram

The water level automatic control soft start circuit of SHD201 single water supply pump is as follows:

In the figure, the SDJ electrode type sensor adopts the HJ-13 type, the KZH water pump control box adopts the HKD-21B type, the 1MK liquid level module adopts the HKC-1SG type, the 2MK signal module adopts the HXC-1 type, and the sY operation sensor adopts the HYC-1 type.

The following figure shows that one soft starter can start and stop two water pumps in sequence. The main feature of the one-to-two solution is that it saves one soft starter, reduces investment, and fully reflects the economy and practicality of the solution.

(1) Starting process: First, select a motor and gradually increase the output voltage according to the selected starting method under the drag of the soft starter. After reaching the power frequency voltage, the bypass contactor is turned on. Then, the soft starter is removed from the circuit to start the next motor.

(2) Stopping process: First start the soft starter and run it in parallel with the bypass contactor, then cut off the bypass, and finally the soft starter gradually reduces the output voltage according to the selected stopping method until it stops.