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In summary: Excel is a great tool for quick plotting.In summary, the equation converts horsepower (rotational power) into torque (linear power), which can be plotted using different power-speed curves depending on the type of electric motor.
- #1
stickers
- 7
- 0
Hi all..
I've been seeing the famous equation which 'converts' horsepower into torque: HP = Torque (lb/ft) * rpm / 5252. The 1/5252 comes from 2*PI/33,000.
Power (rotational) is simply torque * angular velocity, isn't it? When I try to plot the imperial version, I get the typical graph with HP and torque intersecting at 5252rpm. But when I try to plot the same torque values in metric using Power (kW) = Torque (Nm) * rpm * 2*PI/60, I get something wayy different with the power and torque curves not even intersecting.
Am I missing out on something? =/
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- #2
FredGarvin
Science Advisor
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[tex]P(kW) = \frac{T(Nm) * \omega (rpm)}{9549}[/tex]
The 9549 comes from [tex]\frac{60*1000}{2 \pi}[/tex]
You're forgetting the factor of 1000 by the looks of it.
Last edited:
- #3
stickers
- 7
- 0
Ah.. so that's how. I've seen this 9549 number before, but couldn't figure out how it was derived. Thanks!
But I've tried plotting typical values for torque for this equation, and I still don't get the typical curves. That equation means the curves will intersect at 9545rpm isn't it? How do we get the typical curve intersecting somewhere in the middle?
- #4
KLoux
- 176
- 1
What do you mean by the "typical curves?" Do you mean for an automotive engine or for an electric motor? These motors have different characteristics that can make the torque-rpm and power-rpm curves very different.
For example, a typical DC motor torque-speed curve has a flat (constant-torque) region from 0 RPM up to some "base speed," at which point the torque starts to decrease as the speed increases (constant-power region). If you were to overlay a power-speed curve, it would start at zero and increase linearly up to the base speed, at which point it would level off. The curves would not necessarily intersect at the same speed, torque, or power for all DC electric motors. What is true, however, is that at any point on the curve, the torque-power-speed relationship that you and Fred posted holds.
-Kerry
- #5
- #6
mheslep
Gold Member
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FredGarvin said:
It works for me just fine
You use Excel for these quick plots?
- #7
FredGarvin
Science Advisor
- 5,093
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mheslep said:
You use Excel for these quick plots?
Yup.
Related to Power/Torque Relations: Exploring the Imperial vs. Metric Equations
1. What is the difference between power and torque?
Power and torque are both measurements of force, but they represent different aspects of force. Power is a measurement of how quickly work is done, while torque is a measurement of rotational force.
2. Why are there different equations for power and torque in the imperial and metric systems?
The imperial and metric systems use different units of measurement for force and distance, which results in different equations for calculating power and torque. The imperial system uses units such as pounds and feet, while the metric system uses units such as newtons and meters.
3. Which system is more commonly used in the scientific community?
The metric system is more commonly used in the scientific community due to its simplicity and consistency. It is also the preferred system in most countries around the world.
4. How do I convert between the imperial and metric equations for power and torque?
To convert between the imperial and metric equations, you can use conversion factors. For example, to convert from pounds to newtons, multiply the value in pounds by 4.448 to get the equivalent value in newtons.
5. Are there any advantages to using one system over the other when it comes to power and torque calculations?
Both systems have their own advantages and disadvantages. The imperial system may be more familiar to individuals in certain countries, while the metric system offers easier conversions and more consistent units. Ultimately, the choice of which system to use for power and torque calculations depends on personal preference and the requirements of the project or experiment.
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