There is no direct mechanical connection in the coupler, and the power is transmitted entirely by the kinetic energy of liquid. If there is no liquid filling, there is no connection between the pump wheel and the turbine port in the coupling. When the pump rotates and the turbine does not turn, the input and output terminals cannot be coupled to connect, and the torque and power can not be transferred, so the coupler must properly fill the liquid according to the regulations.
Why is the power of a coupler transmitting power generally proportional to the filling rate? Because hydraulic couplings depend on the kinetic energy of liquid to transmit power, so in the prescribed range of liquid filling, the more fluid is filled, the greater the transmission power. The less liquid charge, the smaller the transmission power. The power transmission capacity of a hydraulic coupling is generally proportional to its filling rate.
Before starting, the auxiliary cavity below is filled with working fluid, which lowers the oil filling rate of the working chamber, reduces the starting torque and makes the start-up smooth and soft. Conversely, if the auxiliary cavity is located above, when the hydraulic coupling starts, the 100% oil in the working chamber makes the starting torque and starting impact increase, which is not conducive to the smooth start of the machine.
It has a no-load starting motor, stable stepless speed etc., for power plant feedwater pump speed regulation, can simplify the boiler feedwater control system, reduce the number of high pressure valve, because through the speed change water and pressure to meet the unit start stop and load change, good regulation characteristics, the valve pressure drop is small, line loss that is not easy to damage, so that the water supply system to reduce the fault, when the water pump jam and seizure occurs, the pump and motor can play a protective role. Therefore, in the modern power station, the water supply pump of the unit boiler is generally adopted by the speed regulating feed water pump with the hydraulic coupling.
