# Explain the relationship between output speed and torque

### What's the difference between torque and horsepower? | HowStuffWorks

Torque/Speed Curves; Power Curves Torque, as defined in University Physics, 8th ed. , by Hugh Thus, if we change the effective length of the handle, we change the torque (see equation 1). . In other words, there is a tradeoff between how much torque a motor delivers, and how fast the output shaft spins. The following calculations show the relationship between power, torque and rotational speed The principle is best explained with an example. speed reduction of 25 through the gearbox with a standard input speed for an electric motor of. The inverse relationship between speed and torque means that an increase in the load (torque) on the motor will FAQ: What are rotational losses in DC motors? The relationship between voltage and DC motor output speed.

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.

• Understanding D.C. Motor Characteristics
• What's the difference between torque and horsepower?

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 [1], the output of the PI controller is translated into duty cycle for the PWM generator. In topology [2], the output of the PI controller is translated to be the reference current for hysteresis current controller. 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 [1] 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. 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.

## - Power and Torque -

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. Definitions of terms used in our data sheet can be found below with links generously distributed across the article for further reading.

### Torque relationship to speed in a DC motor - Electrical Engineering Stack Exchange

Ultimately, the two terms represent the same value — the rotational force applied to the output shaft. Depending on the application, this parameter will affect the rate at which a particular function is executed and it may have a significant effect on the overall performance of the device.

Although this example may be outdated, audio cassettes are a great way of explaining how some applications need to vary the torque to match a changing load.

As the cassette plays and the audio tape moves from one spindle to the other, the driving motor will experience a change in load. However, the playback must remain at a constant speed throughout — otherwise the audio pitch would be affected.

Pulleys and lifts often experience this, the motor stops at an extremity as the load is attached or removed. Here, keeping a constant speed is not as important as the motor being able to handle a range of different torque loads as moving a heavier object requires more output torque than a light object or no load.

Each of these applications has the common theme of a varying load attached to the motor. If your application involves a fixed load, then it is likely that you will be more interested in varying the speed. The ability to vary motor speed whilst maintaining a steady torque is essential to many applications for a variety of reasons. An example of an application that requires a variable speed and steady torque is an audio CD player as it is commonly observed that the CD will rotate faster at certain points than others.

This means that the speed must be decreased as the laser is reading from the outermost tracks because there is more information per revolution. Inversely, the speed is increased as the laser reads from the innermost tracks as the spiral circumferences are smaller and therefore contain less information per revolution.

Without the ability to adjust the motor speed with the voltage whilst maintaining this constant torque, it would be very difficult to read and play this information at a steady rate. This same principle can be applied to a wide variety of applications and is often critical to their successful operation. Many of our DC motors and gear motors can operate across a wide variety of speeds and loads, this allows our customers to explore the possibilities of their project and usually reach a suitable solution with a single motor.

How to read the Typical Performance Characteristics Chart The Typical Performance Characteristics chart appears on the front page of each of our data sheets.

This graph is an extremely useful tool that illustrates the typical behaviour of an individual motor. As we have previously discussed, many of our customers are looking for a motor or gear motor that will operate at a given speed and load. One of the best places to find a solution is our online catalogue and we can always help to recommend suitable motors and discuss customisation options.

## Application Notes

This means that the data sheet values for speed are taken under controlled and specific conditions and do not represent the full capabilities of any single motor. This is where the typical performance chart is a useful tool to view a wider range of the motor capabilities.

The blue line on the Typical performance Chart above shows the speeds at which the motor will operate between a point of no-load all the way up to its stall torque approx.

For example; if a customer requires a steady speed and torque of RPM and 0. Rated load — 0. The image above illustrates this and demonstrates that the is, in fact, suitable for the customer based on their fixed speed and torque requirements.