Why do I calculate high efficiency for the multi-stage centrifugal pump?
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The unit is equipped with multi-stage centrifugal pumps; currently, it has 9 stages. The data collected at the production site are as follows: inlet pressure of 0.06 MPa, outlet pressure of 14.8 MPa, and hourly discharge of 336 m3/h. The motor has a rated power of 2000 kW, a rated voltage of 6000 V, and an operating current of 174 A. The power factor indicated on the nameplate is 0.88, while the efficiency specified on the nameplate is 96%. Using these values and relevant formulas, the pump efficiency calculated to be 90%, which clearly does not correspond to reality; the efficiency of a centrifugal pump should be around 80% at most. I’m not sure what the issue is. Those with experience, please advise me – could it be that the calculation method is incorrect, or are there problems with the actual data? Where is the most likely source of the problem?
This post was last edited by Ah on 2016-6-3 14:25. What is the material density? What is the motor power factor? Haven’t you considered the motor’s power factor?
This post was last edited by A Le on 2016-6-6 08:51. I made a mistake; please forgive me
Could you give me the formula you’re using? Thank you
I roughly calculated it to be a little over 85%. Active power: P=1.732*U*I*COSψ, derived by reversing the pump efficiency formula
Effective work of the pump: 336*（14.8-0.06）*1.02*100/102/3.6=1375.73. Motor output power: 1.732*6000*174*0.88*0.96=1527.57. Pump efficiency = 1375.73/1525.57 = 90%. The density is that of water; it’s a bit high
It is recommended to check your flow meter as well as the actual input voltage. Normally, the actual input voltage of the motor is higher than the voltage specified on the nameplate. As for the efficiency of the motor, it is also related to the actual operating point of the motor.
The material is water, with a power factor of 0.88. The figures I calculated, as well as those calculated by other users online, are all 90% – I’m not sure how you arrived at that figure
There’s an issue with your calculation; is 336 m3/h the rated flow rate? The efficiency, power factor, and operating current of motors vary with different loads. It cannot be calculated using the parameters at the rated point fixedly.