Power and Torque: Understanding the Relationship Between the Two, by EPI Inc.
However, when you are talking about the relationship between speed and torque of a DC motor, then you have to think about it differently. Then there is a relation between the torque and the speed! . In topology , the output of the PI controller is translated into duty cycle for the. Torque, moment, or moment of force is the rotational equivalent of linear force. The concept Relationship between force F, torque τ, linear momentum p, and angular momentum L in a system which has Algebraically, the equation may be rearranged to compute torque for a given angular speed and power output.
With Controller At this point, we don't discuss about PI controller first. Sometimes, we need to control the current, e. As mentioned earlier, the starting current inrush current is very high. This starting current might damage the motor, but usually motor winding is capable of carrying this amount of high current for a short duration say 10s before the insulator of the winding fails.
Current limit controller or current controllerusually, is required to protect the power electronic drive, especially the power rating of the drive is lower than the inrush current. Well, we discuss a bit about current controller.
Probably we focus on hysteresis type of current controller. In this controller, when the motor current rises above a threshold, the controller will issue a command to turn-off the power electronic drive. On the other hand, when the motor current is lower than the reference current, the controller will turn on the power drive.
Okay, let's discuss the motor operation now. When the power is turned on, motor current will rise rapidly due to low E. When the controller detects that motor current is above the current limit, it will switch off the voltage supply to motor.
If we observe the voltage waveform when motor accelerates from 0 - RPM with an osiloscope, we will see that at beginning, the voltage waveform across motor terminals are chopped, when the E is low. However, after that, there is no chopping anymore because at higher speed, E is large enough to limit the current below the rated value or safety level. In topology , the output of the PI controller is translated into duty cycle for the PWM generator.
In topology , the output of the PI controller is translated to be the reference current for hysteresis current controller.
What is the relationship between the torque and speed?
For example, if the motor current is above the the reference current, the hysterisis controller will cut of the supply to the motor, and vice versa. If you're interested, you can study the model given in one of my posts https: Well let's talk about the motor operation now. Topology  In this section, we assume that the power rating of the power electronic drive is very high until we do not need to protect the switches.
The duty cycle issued by PI controller will reduce how fast it reduces depends on the setting of PI controller when the motor speed approaches wref. The objective of the PI controller is to 'amplify' the speed error in such away that it responses faster better dynamic to achieve the required speed.
- Power and Torque -
This value is slightly larger than E because this potential difference is required to produce a current that is just enough to overcome the damping torque. Topology  Power rating of power switches is also assumed to be infinite in this section. So, protection scheme is ignored here. When the power is on, the werr is MAX.
Torque relationship to speed in a DC motor - Electrical Engineering Stack Exchange
So, the PI controller will issue a reference current depends on the setting of PI controller that is larger than motor current. Then it applies various factors air temperature, barometric pressure, relative humidity in order to correct the observed power to the value it would have been if it had been measured at standard atmospheric conditions, called corrected power.
Power to Drive a Pump In the course of working with lots of different engine projects, we often hear the suggestion that engine power can be increased by the use of a "better" oil pump. Implicit in that suggestion is the belief that a "better" oil pump has higher pumping efficiency, and can, therefore, deliver the required flow at the required pressure while consuming less power from the crankshaft to do so.
While that is technically true, the magnitude of the improvement number is surprisingly small. How much power does it take to drive a pump delivering a known flow at a known pressure? We have already shown that power is work per unit time, and we will stick with good old American units for the time being foot-pounds per minute and inch-pounds per minute. Since flow is more freqently given in gallons per minute, and since it is well known that there are cubic inches in a gallon, then: Since, as explained above, 1 HP is 33, foot-pounds of work per minute, multiplying that number by 12 produces the number of inch-pounds of work per minute in one HPDividingby gives the units-conversion factor of Therefore, the simple equation is: When the equation is modified to include pump efficiency, it becomes: So suppose your all-aluminum V8 engine requires 10 GPM at 50 psi.
The oil pump will have been sized to maintain some preferred level of oil pressure at idle when the engine and oil are hot, so the pump will have far more capacity than is required to maintain the 10 GPM at 50 psi at operating speed. That's what the "relief" valve does: It is actually pumping roughly 50 GPM 10 of which goes through the engine, and the remaining 40 goes through the relief valve at 50 psi.
The power to drive that pressure pump stage is: That pump at the same flow and pressure will consume: General Observations In order to design an engine for a particular application, it is helpful to plot out the optimal power curve for that specific application, then from that design information, determine the torque curve which is required to produce the desired power curve. By evaluating the torque requirements against realistic BMEP values you can determine the reasonableness of the target power curve.
Typically, the torque peak will occur at a substantially lower RPM than the power peak. For a race engine, it is often beneficial within the boundary conditions of the application to operate the engine well beyond the power peak, in order to produce the maximum average power within a required RPM band. However, for an engine which operates in a relatively narrow RPM band, such as an aircraft engine, it is generally a requirement that the engine produce maximum power at the maximum RPM.
That requires the torque peak to be fairly close to the maximum RPM. For an aircraft engine, you typically design the torque curve to peak at the normal cruise setting and stay flat up to maximum RPM.
That positioning of the torque curve would allow the engine to produce significantly more power if it could operate at a higher RPM, but the goal is to optimize the performance within the operating range. An example of that concept is shown Figure 3 below. The three dashed lines represent three different torque curves, each having exactly the same shape and torque values, but with the peak torque values located at different RPM values. The solid lines show the power produced by the torque curves of the same color.
Again, moving the same torque curve to the right another RPM blue, lb-ft torque peak at RPM causes the power to peak at about HP at RPM Using the black curves as an example, note that the engine produces HP at both and RPM, which means the engine can do the same amount of work per unit time power at as it can at The RPM band within which the engine produces its peak torque is limited.
You can tailor an engine to have a high peak torque with a very narrow band, or a lower peak torque value over a wider band. Those characteristics are usually dictated by the parameters of the application for which the engine is intended.
An example of that is shown in Figure 4 below.