Hp power use

[roughshawd]

Is a higher horse power motor more demanding for power, than a small horse power motor, or is the application important for a toss up ? Reason is I have a shallow well that had a 1/2 hp motor, but I put a 3/4hp in because I added four gardens that requires irrigation. The new pump is doing fine, but as far as pressure recovery is concerned, a 1hp pump would be faster I am sure, only reason I am asking is about saving money on the 220v bill. My electric went up $89.00 in one month...

 

[ivak245]

The 3/4 HP will draw more than the 1/2 HP (560w or 370w). Did you change the pump/electric motor or just the motor.? If you are using the same pump with a bigger motor driving it, there's your increase.

 

[Bluejets]

All depends on the load.................

 

[danadak]

Not a motor expert here but I would think its both mechanical size, eg. bigger more
inertia to overcome = more energy, and load as Bluejets posted ? If motor being
cycled infrequently then maybe not as big a consideration.

But seems complicated, look at images/google -

"motor load versus size power consumption versus start stop graph"


Regards, Dana.

 

[crutschow]

Did you install a new pump with motor or just a new motor?
The power drawn by a motor is basically determined by its load and wouldn't change much with the motor rating for the same load.
You electric bill will be mostly determined by the amount of water you use, not the size of the pump.
All the size of the pump does is determine how fast you can pump a given amount of water.

 

[crutschow]

I would think its both mechanical size, eg. bigger more
inertia to overcome = more energy

The inertia of a steady load has no effect on the power, only the energy required to get it to speed.

 

[Bluejets]

I imagine single phase split-phase motor.......these can exibit rather strange ( possibly explainable) characteristic in that, when on no load, can draw almost as much current as near full load.
As load comes on. load current drops and then goes back up again as load increases.
Did bench tests on this yongs ago.
Possibly something to do with the rotor slip ( or less in this scenario)

 

[crutschow]

these can exibit rather strange ( possibly explainable) characteristic in that, when on no load, can draw almost as much current as near full load.

That could be reactive (inductive) current that generates the magnetic field.

 

[Bluejets]

Only happens in single phase motors as above.

 

[Minder]

On a radial blade pump, the load current will also drop as the output is throttled down.
IOW, it draws full load current when no output delivery is connected.

 

[Bluejets]

Centrifigul pumps such as in large irrigation, we throttle the output ( turn the output valve off ) to lower the load.
Both when the pipe was initially empty and to lower the full load current.
Result was to let the impeller "thrash"