Problems with the current in the centrifugal pump motor
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I went to a factory today; it involves a centrifugal pump of the IS200-150-315 model, with a flow rate of 374 cubic meters per hour, a head of 28 meters, and a motor power of 45 KW. The pump sends fluid through 3 elbows to a location on the 6th floor at a height of about 18.5 meters. However, the motor current was only 62 A. Is there something wrong? It seems that the power has decreased, while the pressure head remains unchanged; it’s likely that the flow rate has reduced. I’m not sure if that’s correct Is the pump’s efficiency too low? Is it because the motor used is too large? 35 kW would be sufficient, wouldn’t it?
The characteristics of a centrifugal pump are more intuitively understood by referring to the motor’s rated current. High flow rate means high current. High pressure, low current. For reference.
I think if the current is low, the work done will definitely be poor, because the resistance in the pipes remains constant. So according to the formula W=HQp/102, the flow rate decreases – is that correct?
What I mean is that on-site, it is necessary to compare the actual working capacity with the pump’s design capacity to see if they match. If the standards are not met, the involvement of the relevant design department is necessary; it’s not something that can be determined by a simple formula. Since the current is below the device’s rated value, it is necessary to investigate the cause in the piping system; check whether there is any blockage in the suction pipe and whether the piping downstream of the pump is unobstructed. Also, whether the user has not reached the designed traffic level. One needs to go to the site to check; a current value can reveal everything. For reference.
I suspect that the flow rate doesn’t meet the requirements; there are no flow meters installed on the main pipelines, otherwise it would be obvious at a glance.