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the bearing wear and heating are reduced, and the Mechanical Service Life of the pump and the motor is prolonged. 3) because the constant pressure automatic control is realized, it does not need the operator to operate frequently, which reduces the Labor intensity of the personnel and saves manpower. 4) the pump motor adopts the soft start mode, accelerates according to the set acceleration time, there is no starting impulse current, which avoids the impact of the current when the motor starts, which causes the fluctuation of the grid voltage, and also avoids the surge of the pump system caused by the sudden acceleration of the motor. 5) it has soft start and soft stop function, which can prevent water hammer. 6) because the variable displacement pump works in the condition of frequency conversion, its speed is decided by the amount of water supplied from outside during its operation, so the system can save considerable electric energy during its operation, and its economic benefit is very obvious. Because of its power-saving, so the system has a quick return on investment, and long-term benefits, its social benefits are also very large.