The main drive system of this series speed hydraulic coupling is driven by the original motive force of the pump wheel rotor. The pump wheel passes the energy to the turbine rotor through the working fluid in the working chamber, and the turbine rotor drives the operation of the working machine. The device is open type, with radial bearing support, an independent working oil system and lubricating oil system. The lubricating oil system uses the gear pump to supply oil. The oil system uses the vane pump (or gear pump) to supply oil. The oil quantity is adjusted by the regulating valve, the discharge flow of the working oil is adjusted through the spoon pipe, and the spoon pipe is passed through the spoon pipe. Adjust the output speed and adjust the range to 20%-100%.