Abstract : The application of variable frequency speed control technology has become a new direction in the development of water flow standard test devices in recent years. Through the analysis of the operating efficiency of centrifugal water pumps and the energy-saving effects of different flow regulation methods, a multi-frequency converter speed control system with significant energy-saving effects is proposed for water flow standard test devices using multiple centrifugal water pumps as power sources. Keywords : Water flow standard test device; frequency converter; energy saving; Centrifugal water pumps are used as testing and verification devices for liquid flow meters. Water flow standard test devices require a very stable flow source that is continuously adjustable over a wide range. Although traditional water tower pressure stabilization methods can meet these requirements well, the following reasons make the replacement of elevated water towers with variable frequency speed control systems an inevitable trend: ① High cost of building water towers; ② Water tower overflow causes serious energy waste; ③ Continuous improvement and price reduction of frequency converter technology. Researching a variable frequency speed control system that can meet the requirements of flow testing and verification while also achieving ideal energy-saving effects is an urgent need for the development of water flow standard test devices. The variable frequency speed control system of a water flow standard test device is not suitable for the constant pressure water supply mode widely used in ordinary water supply systems. Because: In constant pressure water supply systems, multiple pumps are typically controlled by a single frequency converter in a cyclic manner. This operating method makes it difficult to ensure that the flow rate remains stable and adjustable throughout the entire range. Furthermore, the network characteristics and flow variation patterns of the water flow standard test device are fundamentally different from those of ordinary water supply systems, and the constant pressure throttling regulation method cannot fully utilize its energy-saving potential. The following analysis of the operating efficiency of centrifugal pumps and the energy-saving effects of different flow regulation methods proposes a multi-frequency converter speed control system with significant energy-saving effects. 1. High-Efficiency Operating Range of Centrifugal Pumps The actual operating efficiency of a centrifugal pump should not be lower than 90% of its maximum efficiency. Based on this, points A and B can be determined on the characteristic curve of the centrifugal pump (curve 1 in Figure 1). Then, according to the similarity theorem, equivalent lines 2 and 3 passing through points A and B are drawn. The area between curves 1, 2, and 3 is the high-efficiency range of the centrifugal pump. Considering that the efficiency of the motor and frequency converter will decrease significantly when the speed is below 50% of the rated speed, the meaningful high-efficiency range is the area enclosed by curves 1, 2, 3, and 4. [b][align=center]For details, please click: Application of Frequency Converters in Water Flow Standard Test Devices[/align][/b]