| 摘要 |
PURPOSE:To make it possible to control the proper number of driving pumps in response to the discharge flow rate and pressure in such a way that in plural number of pumps which are composed of constant-speed driving pumps and a variable-speed driving pump including a variable frequency inverter, the number of running constant-speed driving pumps is varied in response to the frequency of the inverter. CONSTITUTION:For only P1 pump among a plurality of pumps P1-Pn, its AC motor M1 is driven at variable speeds with a variable frequency inverter 4, and other motors M2-Mn are driven at a constant speed by means of Ac power supply 12. Though the frequency of the inverter 4 is set through a frequency controller 8 after comparing pump discharge signals H which are detected by a pressure signal generator 5 with set pressure H0 from a pressure setter 6 using a pressure controller 7 when inverter frequency f rises or falls, and arrives at the determined limit, a number of running pump discriminating circuit 20 gives signals as output in response to it, and increases and decreases the number of running motors. |
