【A journey of a thousand miles begins with a single step – Centrifugal Pumps】1.1 Understanding the concept: Power

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This post was last edited by 3983596_FPPZ on 2018-11-14 at 15:34. Power 1.1.5 Power is the work done or energy converted by an object per unit of time; the common unit for measuring it is the kilowatt, denoted as kW. Horsepower, abbreviated as hp, is also used. In pump products, there are three types of power that we often encounter: ● Motor power – The rated motor power is calculated as: Motor power = √3 × rated voltage × rated current × power factor； Rated power is a specified power value, representing the mechanical power output by the motor under specified voltage and frequency conditions. It is generally required that the load not exceed the motor’s rated power to prevent damage to the motor. Motor input/output power: Motor input power * Motor efficiency = Motor output power; both the input and output powers of the motor are actual power values that vary depending on the load. Motor efficiency is generally very high; smaller motors have an efficiency of around 90%, while larger motors achieve an efficiency of 95% or more. ●Shaft power: Under certain flow rates and head values, the power delivered to the pump shaft by the prime mover per unit of time is referred to as shaft power. Shaft power = motor output power * coupling efficiency = flow rate * head * specific gravity / pump efficiency. The efficiency of different transmission methods varies; while the efficiency of couplings is always above 95%, the efficiency of belt drives, universal joints, hydraulic couplers, etc., is slightly lower. ● Useful power: The useful power of a pump refers to the useful energy that the liquid receives from the pump per unit of time, which is the actual power that the liquid gains in a valuable form. Effective power = Shaft power * Pump efficiency. Homework questions (multiple choice): Which of the following are not among the common rated power values for standard industrial motors? A. 5.5kW B. 7.5kW C. 10.5kW D. 18.5kW E. 22kW F. 32kW G. 45kW H. 65kW I. 85kW J. 132kW CFHI