Finding the Right Electric Motor for My Pump Setup

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Discussion Overview

The discussion revolves around selecting an appropriate electric motor for a pump setup that requires specific operational parameters, including 3600 RPM and 24 lb.ft. of torque. Participants explore the implications of using a 24VDC power supply and the necessary gearbox design to achieve these requirements.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant outlines the need for a motor that can provide 3600 RPM and 24 lb.ft. of torque, emphasizing the importance of gearbox design in determining the appropriate motor specifications.
  • Another participant calculates the power requirements, indicating that to produce 16 HP (12 kW) at 24VDC, a current of 500 A would be necessary, which raises concerns about the feasibility of such a setup.
  • A different calculation suggests that the required power is actually 1950 W, leading to a current requirement of 81.3 A, although another participant later disputes this by presenting a different calculation that results in a much higher current requirement of 511 A.
  • One participant discusses the formula for power in rotational motion, noting the importance of including the factor of 2π in calculations related to torque and angular velocity.
  • A participant expresses curiosity about the materials used in generator head assemblies, questioning whether alternatives to traditional metals could be viable based on magnetic properties and eddy currents.
  • Another participant clarifies that electric machine cores are typically laminated from ferromagnetic sheets to minimize eddy current losses, rather than being cast from solid materials.

Areas of Agreement / Disagreement

There is no consensus on the exact power requirements or the feasibility of achieving the necessary amperage with the given power supply. Multiple competing views on the calculations and material choices for generator assemblies remain unresolved.

Contextual Notes

Participants present various calculations and assumptions regarding power requirements, which depend on specific definitions and interpretations of the problem. The discussion reflects uncertainty about the practical implications of the electrical requirements and the materials used in generator design.

Possibilites
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OK, here's my dilemma:

I have a pump that requires 3600RPM, 24lb.ft. of torque (optimally) to run it. It was attached to a gasoline powered 16HP motor, and I need it to run off of an electric motor now.

Not so difficult, you say?

My only power supply is limited to 24VDC.

I am looking for someone who has expert knowledge on gearbox design/development. It is unknown as to which 24VDC motor will be required to achieve the above 3600RPM, 24lb.ft. Torque, because the gear ratio(s)/gearbox has to be addressed first. It is working the equation in reverse, I know, but it's the only way apparently.

Please think your answers through!
Thanks for any help.
 
Last edited:
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You do realize that to produce 16 hp (12 kW) of power, you need a current of 500 A with 24 VDC (not counting losses). No matter what motor you use or what gearbox you have, you will need that 500 A current; Which, according to http://en.wikipedia.org/wiki/American_wire_gauge#Table_of_AWG_wire_sizes", requires, at least, TWO 4/0 wires (but I'm no electrician).
 
Last edited by a moderator:
Possibilites said:
OK, here's my dilemma:

I have a pump that requires 3600RPM, 24lb.ft. of torque (optimally) to run it. It was attached to a gasoline powered 16HP motor, and I need it to run off of an electric motor now.

Not so difficult, you say?

My only power supply is limited to 24VDC.

I am looking for someone who has expert knowledge on gearbox design/development. It is unknown as to which 24VDC motor will be required to achieve the above 3600RPM, 24lb.ft. Torque, because the gear ratio(s)/gearbox has to be addressed first. It is working the equation in reverse, I know, but it's the only way apparently.

Please think your answers through!
Thanks for any help.

The required power is:

[tex] 3600 \frac{1}{\mathrm{min}} \, \times \frac{1 \mathrm{min}}{60 \, \mathrm{s}} \times \frac{24 \mathrm{lb. \, ft.}} \times \frac{1 \, \mathrm{HP}}{550 \, \mathrm{lb. \, ft. \, s}^{-1}} = 2.62 \, \mathrm{HP} \times \frac{745.7 \, \matrm{W}}{1 \, \mathrm{HP}} = 1950 \, \mathrm{W}[/tex]

which, on 24 V voltage would require a constant current of:

[tex] 1950/24 = 81.3 \, \mathrm{A}[/tex]
 
Dickfore said:
The required power is:

[tex] 3600 \frac{1}{\mathrm{min}} \, \times \frac{1 \mathrm{min}}{60 \, \mathrm{s}} \times \frac{24 \mathrm{lb. \, ft.}} \times \frac{1 \, \mathrm{HP}}{550 \, \mathrm{lb. \, ft. \, s}^{-1}} = 2.62 \, \mathrm{HP} \times \frac{745.7 \, \matrm{W}}{1 \, \mathrm{HP}} = 1950 \, \mathrm{W}[/tex]

which, on 24 V voltage would require a constant current of:

[tex] 1950/24 = 81.3 \, \mathrm{A}[/tex]

Actually, it is:

[tex] 3600 \frac{\mathrm{rev}}{\mathrm{min}} \, \times \frac{2 \pi \mathrm{rad}}{1 \, \mathrm{rev}} \times \frac{1 \mathrm{min}}{60 \, \mathrm{s}} \times 24 \mathrm{lb. \, ft.} \times \frac{1 \, \mathrm{HP}}{550 \, \mathrm{lb. \, ft. \, s}^{-1}} = 16.45 \, \mathrm{HP} \times \frac{745.7 \, \matrm{W}}{1 \, \mathrm{HP}} = 12 267 \, \mathrm{W}[/tex]

which, on 24 V voltage would require a constant current of:

[tex] 12 267/24 = 511 \, \mathrm{A}[/tex]
 
Ahh, yes! The formula for power due to rotational motion is:

[tex] P = \tau \omega[/tex]

where [itex]\tau[/itex] is the torque and [itex]\omega = 2\pi f[/itex] is the angular velocity (circular frequency). I forgot the factor of [itex]2\pi[/itex] in my previous calculation.
 
I see.
In other words, it is outside my capacity to establish that much amperage in the current situation, and I thank you for the information.

Perhaps another?
In general, I am curious as to what material makes up the internal rotational section of a generator head assembly (not the Cu wire, rather the "frame" it is mounted onto{stator assembly?})?
Cast Al?
Cast Fe?


Why was that particular material chosen for that item?
I am trying to determine whether it has anything to do with magnetic properties, eddy currents, or if it can be made of a hardened polymer and still function inside a generator head assembly as it's intended, instead of using the heavier metal(existing) counterpart?
 
Cores of electric machines are not cast, but laminated, i.e. built of layers of ferromagnetic sheets (usually steel alloys which differ in magnetic properties depending on application) in order to avoid losses due to eddy currents.
 
Thanks again for the useful input. I seem to be batting a very low average with some things i am trying to study.
 

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