Abstract: A power-saving optimization operation method and switching point determining method for a water pump unit. In the parallel water pump units, k water pumps converters form a sub-pump unit A. The water output Q1 of a first water pump in the sub-pump unit A, the input power P1 of the frequency converter corresponding to Q1 and the operating frequency f1 of the frequency converter corresponding to Q1 are recorded, where QA=Q1, PA=P1. The QA-PA curve of an operating water pump serves as the working curve w1, where QA=mQ1 and PA=mP1, and k?m?2. The working curve wm of m operating water pumps operating at the same frequency is obtained, where f1=f2= . . . =fm. The intersection point of the working curve wm-1 and the working curve wm is the optimal switching point between m-1 operating water pumps and m operating water pumps under the constant pressure Hs.

Abstract: A power-saving optimization operation method and switching point determining method for a water pump unit. In the parallel water pump units, k water pumps converters form a sub-pump unit A. The water output Q1 of a first water pump in the sub-pump unit A, the input power P1 of the frequency converter corresponding to Q1 and the operating frequency f1 of the frequency converter corresponding to Q1 are recorded, where QA=Q1, PA=P1. The QA?PA curve of an operating water pump serves as the working curve w1, where QA=mQ1 and PA=mP1, and k?m?2. The working curve wm of m operating water pumps operating at the same frequency is obtained, where f1=f2= . . . =fm. The intersection point of the working curve wm?1 and the working curve wm is the optimal switching point between m?1 operating water pumps and m operating water pumps under the constant pressure Hs.

Abstract: A backrest adjustor comprises a shell, a rotary gear located inside the shell, a winding wheel which is driven by the gear and located inside the shell, a knob for driving the gear to rotate, and a button capable of controlling the gear to rotate, moving and being reset by a reset component. A rotating portion of the knob is exposed outside the shell. The backrest adjustor further comprises a ribbon, the middle segment of which is wound on the winding wheel while two ends of which used for connecting a frame of a baby carriage extend from the shell and are then wound around the outer face of the backrest.