You often hear the term motor torque when you look at electric motors. Motor torque describes the tendency of a force to cause rotation. When you ask what is torque, you find that it measures how much a force can make something turn. In a motor, torque happens when current flows through the rotor inside a magnetic field. You use torque to determine how much twisting force a motor can deliver to move loads. You calculate motor torque with formulas such as T = F × R × sin(θ), where F is the force, R is the radius, and θ is the angle. What is torque in practical terms? It is the force that lets a motor turn wheels, gears, or other parts. Knowing what is torque helps you choose the right motor for your machines and applications.

Wichtigste Erkenntnisse

• Motor torque is the twisting force that makes motors turn shafts or wheels, and it depends on force, distance from the pivot, and the angle of force application.

• Torque motors provide high torque at low or zero speeds, offering precise control and reducing the need for gears in many industrial applications.

• Electric motor torque comes from the interaction of current and magnetic fields, with design factors like magnets, windings, and cooling affecting torque output.

• Accurate torque measurement uses sensors like strain gauges and dynamometers, which help ensure motor performance, safety, and efficiency.

• Understanding the torque-speed relationship and proper motor sizing helps match load needs, improve efficiency, and avoid motor damage or energy waste.

Motor Torque Basics

What Is Torque

When you ask what is torque, you look at the force that causes something to rotate around an axis. In physics and engineering, torque is the rotational equivalent of force. You see torque in action every time you use a wrench to loosen a bolt or push a door open. The farther you apply force from the pivot point, the more torque you create. This principle helps you understand why a longer wrench makes it easier to turn a stubborn bolt.

• Torque depends on three main things:

  • The size of the force you use.

  • The distance from the axis (called the lever arm).

  • The angle between the force and the lever arm.

You can use the formula for torque:
Torque = Force × Distance × sin(θ)
Here, θ is the angle between the force and the lever arm. Only the part of the force that acts at a right angle to the lever arm creates torque. If you push straight toward the pivot, you get no torque.

Tip: When you want to increase torque, use more force, increase the distance from the pivot, or push at a right angle.

In electric motors, you use motor torque to turn shafts, gears, and wheels. Motor torque is the twisting force that makes the motor spin and do work. You need to know what is torque because it tells you how much load your motor can handle. High torque means your motor can move heavier loads or start moving from a stop more easily.

Torque Units

You measure torque using units that combine force and distance. The most common unit in the SI system is the Newton-meter (Nm). In the Imperial system, you use pound-foot (lbf·ft) or pound-inch (in·lbf). You may also see kilogram-force meter (kgf·m) in some metric applications. Accurate conversion between these units is important for safety and performance.

For example, if you have a torque value in pound-foot, you multiply by about 1.36 to get Newton-meters. If you use pound-inch, you multiply by about 0.113. You need to use the right unit when you select a motor or check its performance. This helps you avoid mistakes and keeps your machines running safely.

Torque Motor Overview

A torque motor is a special type of electric motor. You use a torque motor when you need high torque at low speeds or even at zero speed. This kind of motor can keep producing high torque without overheating, even if it is not spinning. You find torque motors in many industries because they offer high torque density, high precision, and low maintenance.

• Key features of a torque motor:

  • High torque at low or zero speed

  • Compact design

  • High precision and control

  • Low noise and vibration

  • Reduced need for gears

You see torque motors in robotics, CNC machines, conveyor belts, cranes, and food processing equipment. In these applications, you need high torque for accurate movement and control. For example, a torque motor in a robot arm lets you move heavy parts smoothly and stop exactly where you want. In digital printing, a torque motor gives you precise control over conveyor belts.

You choose a torque motor when you want high torque, excellent precision, and reliable performance. This makes torque motors essential in industries like aerospace, semiconductor manufacturing, medical devices, and packaging. You get the benefits of high torque and low speed without extra gears or complicated systems.

Note: When you select a torque motor, always check its high torque rating and make sure it matches your application’s needs.

Torque Generation Principles

Torque in Electric Motors

You see torque produced in electric motors when current flows through the windings inside a magnetic field. The electric current interacts with the magnetic field, creating a force that turns the rotor. This force gives you the high torque needed to move loads or start machines. The amount of torque produced depends on several factors:

• Magnetic materials: Using strong magnets, like rare-earth types, increases hohes Drehmoment by improving the magnetic field in the rotor and stator.

• Winding design: More copper windings and higher density boost the magnetic field, which means more torque produced.

• Motor design: The shape of the rotor and stator, plus how you align the magnetic poles, affects how much high torque you get.

• Cooling efficiency: Good cooling lets you push more current through the motor, which increases high torque without overheating.

You use these electric motors principles to design motors that deliver the right amount of dynamic torque for your application. Direct torque control helps you adjust the torque produced quickly and accurately.

Magnetic Field and Current

When you run current through a loop inside a magnetic field, you create torque. The sides of the loop feel equal and opposite forces, which make the loop turn. The formula for this is τ = NIAB sin θ, where N is the number of turns, I is the current, A is the area, B is the magnetic field, and θ is the angle. This shows how electric current and magnetic fields work together to create dynamic torque. The Lorentz force acts on the rotor conductors, making the rotor spin. You use direct torque control to manage this process and get the high torque you need.

Tip: Direct torque control gives you fast response and precise control over the torque motor, which is important for dynamic torque changes.

Synchronous and BLDC Motors

You find differences in how synchronous motors and BLDC motors generate torque. Both types use electric current and magnetic fields, but their control methods and torque output differ.

You get smoother high torque from synchronous motors because they use continuous commutation. The torque of synchronous motor stays steady, which is important for applications needing precise dynamic torque. BLDC motors give you high torque in steps, which can cause torque ripple. Direct torque control in synchronous motors helps you achieve better performance and efficiency. You often choose a torque motor with a synchronous design when you need high torque, smooth power, and advanced control.

Measuring Motor Torque

Measurement Techniques

You can measure torque in an electric motor using several reliable techniques. The most common methods use strain gauge-based rotary and reaction torque sensors. These sensors help you capture the twisting force produced by the motor shaft. You often see reaction-type dual shaft torque sensors and rotating low-range torque sensors in both laboratory and industrial settings. Some sensors, like reaction torque sensors without moving parts, offer high durability. Rotating socket wrench torque sensors use bonded foil strain gauges and slip ring technology to provide precise, bi-directional torque measurement.

• Strain gauge-based rotary torque sensors

• Reaction-type dual shaft torque sensors

• Rotating socket wrench torque sensors

• Reaction torque sensors without moving parts

These techniques allow you to measure torque in electric motor testing, automotive assembly, robotics, and quality control. High-quality sensors ensure you get accurate torque data, which is critical for electric motor performance analysis.

Tools and Instruments

You have access to a wide range of tools and instruments for measuring torque in electric motors. The table below shows some of the most popular options and their features:

You can also use rotary torque transducers, special purpose torque transducers, and mechanical power instruments to measure torque in electric motor systems. These tools help you maintain accuracy and reliability in electric motor testing.

Practical Applications

Precise torque measurement plays a vital role in many real-world electric motor applications. You use transmission dynamometers to measure torque and speed directly from power transmission components. Strain gauge dynamometers let you measure torque on rotating shafts without absorbing power. Torque transducer dynamometers provide continuous, real-time torque monitoring in electric motor systems. Motoring dynamometers simulate different operating conditions for research and development. AC and DC electric dynamometers create controlled loads for testing electric motor performance. Chassis dynamometers measure the power output of entire vehicles, helping you assess electric motor efficiency and drivetrain losses.

Accurate torque measurement ensures you get reliable data for electric motor selection, efficiency calculations, and performance reports. You avoid errors that could affect safety and system performance. Regular calibration and proper maintenance of your torque measurement instruments help you achieve the best results.

Torque-Speed Relationship and Performance

Torque-Speed Curve

You see the torque-speed curve as a key tool for understanding how a motor works. This curve shows that torque stays almost constant at low speeds up to the base speed. After this point, torque drops as speed increases because of field weakening. You notice two lines on the curve: peak torque and continuous torque. Peak torque is the maximum torque a motor can deliver for short bursts, while continuous torque is what the motor can handle without damage. Motors like synchronous motors and torque motors provide high torque at low speeds, which is important for high starting torque and high power density. The power curve rises with speed, peaks, and then falls as torque drops. This torque characteristic helps you select the right motor for your application.

• The torque-speed curve tells you:

  • High torque at low speeds for starting and heavy loads

  • Constant torque up to base speed

  • Variable torque at higher speeds

  • Highest efficiency near rated speed and torque

Load and Efficiency

You must match the load to the motor’s torque to get the highest efficiency. If you oversize the motor, efficiency drops, especially at light loads. The efficiency of electric motors changes with load and speed. Motors reach high efficiency at about 75% to 100% of full load torque. At partial loads, efficiency can fall below 50%. Synchronous motors and torque motors keep high efficiency over a wide range, but faults or poor sizing reduce performance. You should always check the torque-speed relationship and load to avoid wasted energy.

Temperature Effects

Temperature affects torque performance. As the motor heats up, winding resistance increases and magnetic strength drops. This reduces engine torque and high starting torque. The torque-speed curve becomes steeper, so the shaft speed drops more for the same load. Synchronous motors and torque motors can lose dynamic torque at high temperatures. You need to consider real operating temperatures when choosing a motor to ensure it meets your torque and efficiency needs.

Motor Sizing

Proper motor sizing ensures you get the right torque, efficiency, and performance. You must look at the drive mechanism, load, speed, and environment. Synchronous motors and torque motors offer high torque and constant torque for many uses. Use the table below to guide your selection:

If you mismatch torque and speed, you risk stalling, low efficiency, or damage. Synchronous motors and torque motors help you balance high torque, high starting torque, and high efficiency for the best performance.

You have learned that engine torque plays a vital role in how a motor works, whether you see torque in a car or in robotic applications. The table below shows the main points about measuring torque:

When you understand torque, you can size your motor for the right efficiency and performance.

1. You match engine torque to your needs, which improves efficiency and reliability.

2. You reduce maintenance by removing extra parts.

3. You get better control and longer machine life.

Knowing how torque works helps you choose the best motor for any job.

FAQ

What does motor torque measure?

Motor torque measures the twisting force that a motor applies to turn a shaft or load. You use this value to know how much force your motor can deliver for moving or lifting objects.

What affects the amount of torque a motor produces?

You see torque change with factors like current, magnetic field strength, winding design, and temperature. Stronger magnets and higher current increase torque. Heat and poor design reduce it.

What is the difference between peak torque and continuous torque?

Peak torque is the highest force your motor can give for a short time. Continuous torque is the force your motor can safely provide without overheating during regular use.

Tip: Always check both ratings when you select a motor for your project.

What tools can you use to measure motor torque?

You can use torque sensors, torque wrenches, and dynamometers. The table below shows common tools: