Why Does Reducing the output flow also reduce the Motor current??
Why Does Reducing the output flow also reduce the Motor current??
(OP)
Hi sorry if this seems like a stupid qustion but could someone please explain to me why when using a water pump system if you reduce the size of the output pipe i.e by closing a valve the current drawn on the motor turning the water pump is reduced?
We have a problem at the company where i work we have a water scrubber system used for cleaning dust from air.
The system uses a water shear pump powered by an 11.5kw motor. if you try and run the motor with no water passing though it for a few seconds the draw on the motor is 8amps does this seem excessive???
when the system is filled with water the motor pulls 21.5amps which is 1.5amps above the maximum full load current on the motor name plate.
The Company that service the pump say there is nothing wrong with pump as it turns freely enough. and problem must be with are pipework, they are saying that because the other unit that we have is running at 1.5 bar and this problem unit is only running at 0.5bar that we need to slow the water down leaving the pump to increase the pressure which in turn will reduce the current/amps being drwn on the motor. is this correct
Thank you for you time.
A carmichael
manchester england.
We have a problem at the company where i work we have a water scrubber system used for cleaning dust from air.
The system uses a water shear pump powered by an 11.5kw motor. if you try and run the motor with no water passing though it for a few seconds the draw on the motor is 8amps does this seem excessive???
when the system is filled with water the motor pulls 21.5amps which is 1.5amps above the maximum full load current on the motor name plate.
The Company that service the pump say there is nothing wrong with pump as it turns freely enough. and problem must be with are pipework, they are saying that because the other unit that we have is running at 1.5 bar and this problem unit is only running at 0.5bar that we need to slow the water down leaving the pump to increase the pressure which in turn will reduce the current/amps being drwn on the motor. is this correct
Thank you for you time.
A carmichael
manchester england.





RE: Why Does Reducing the output flow also reduce the Motor current??
Reduce flow by increasing discharge pressure = lower power
Increase flow by reducing discharge pressure = higher power
Reduce speed = lower discharge pressure, lower flow and lower power
Increase speed = higher discharge pressure, higher flow,and higher power
Different rules apply for axial flow centrifugal pumps and constant displacement pumps
RE: Why Does Reducing the output flow also reduce the Motor current??
At the bottom of the pump curve there will generally be a power curve which makes this obvious.
RE: Why Does Reducing the output flow also reduce the Motor current??
RE: Why Does Reducing the output flow also reduce the Motor current??
RE: Why Does Reducing the output flow also reduce the Motor current??
Naresuan University
Phitsanulok
Thailand
RE: Why Does Reducing the output flow also reduce the Motor current??
RE: Why Does Reducing the output flow also reduce the Motor current??
Generally I would agree with most of the statements in this thread; however I would recommend that you check the specific speed of the impeller before making any “matter of fact” type statement that the “shut-in HP will be less than open flow HP.”
D23