Water Pump System: Choosing the Right Electrical Motor

[Eng_Luqman]

Dear ...

Please Try To Read Those :

I have This System Of Water Pump Consist Of An Electrical Motor And A Water Pump For Lifting Water From An Underground To The Upground ... In A Factory Using This Pumped Water For Cooling The Iron That Produced Form The Rolling Machines ... (( Open System - To The Atmosphere )) .

And The Main Thing I Want To Know It ... Is To Be Sure Is This System Is Working Correctly With The Bellow Specifications :

Electrical Motor Specifications :

RPM = 2900
V = 380
P = 5.5 Kw
F = 50 Hz
A = 10
3 - Phase Induction Electrical Motor

----------------------------------

Water Pump Specifications :

RPM = 3600
P = 6 HP
H = 30 m
Q = 1000 L / Min.

-----------------------------------

The input and out put line of the pump = 3 inches Pipe


--------------------------------------------------------------

The thing that I want to know it exactly ... how they choosing the this Electrical Motor For This Pump ... Is That Correct ...

On What Formula They Depend ... Or On What Base They Depend To Choose This Electrical Motor For This Water Pump ...

You Can See The RPM For Both Of The E.M. And The Water P.
And How They Arrange The Both ... ?

Hope I can get the right answer and helping to understand the bases and the formulas also in details ...

Regards

 

[anorlunda]

The thing that I want to know it exactly ... how they choosing the this Electrical Motor For This Pump ... Is That Correct ...

They are not perfectly matched. The critical parameter is power. The output power of the motor must equal the power of the pump divided by pump efficiency. For example, if the pump is 6 HP, and its efficiency 80% then it needs 6/0.8 or 7.5 HP of power from the motor. 7.5 HP = 5.6 kw. So the 7.5 kw motor is slightly larger than needed.

You Can See The RPM For Both Of The E.M. And The Water P.
And How They Arrange The Both ... ?

Either the two RPM must be exactly the same, or some gears or belts are needed to change the speed. In your case, the pump probably runs at 2900/3600 or 80% of its rated speed, making the HP and L/sec lower.It sounds like you expect both motor and pump to run at exactly the nameplate values listed. The values are maximums. You probably drive a car rated at 120 mph, but you don't really drive it that fast.