Torque motors from TQ High torque in the smallest installation space
Torque motor: definition and principle of operation
A torque motor is generally a high-pole, permanent-magnet synchronous motor (PMSM). Its electromagnetic design is geared toward high torque, especially at low to medium speeds. The high number of pole pairs supports precise torque generation and control over a wide operating range.
The term torque motor primarily describes the operating behavior and electromagnetic design of the motor. The mechanical design of TQ-RoboDrive's motors is described by the term frameless motor. A frameless motor consists of a separate stator and rotor that are directly integrated into the customer's design.
A motor can combine both properties. In this case, it is referred to as a frameless torque motor.
| Term | Description | Typical Characteristics |
|---|---|---|
| Torque motor | Electromagnetic design and operating behavior | High torque, especially at low to medium speeds |
| Frameless motor | Mechanical design | Stator and rotor are integrated directly into the application without their own housing |
| Frameless torque motor | Combination of design and configuration | Frameless motor with high torque density |
Torque and torque density as key parameters
Torque describes the rotational effect of a motor and is specified in newton meters. It determines how powerfully a motor can accelerate, move, or hold a load in position.
In compact drive systems, however, not only the absolute torque is decisive. An important key figure is torque density. It describes how much torque a motor generates in relation to its volume or weight.
High torque density enables:
- Smaller and lighter drives
- Higher payloads with the same system weight
- More compact robot joints and machine axes
- Greater overall system dynamics
- More design freedom in limited installation spaces
Especially in robotics, medical technology and mobile applications, the weight and size of the motors directly influence payload, energy consumption and motion dynamics. Torque density is therefore often more informative than considering maximum torque alone.
Characteristics of a frameless torque motor
A frameless motor becomes a torque motor when its electromagnetic design is specifically aimed at high torque and high torque density.
The achievable torque density depends on the interaction of several factors:
- Electromagnetic design and magnetic circuit,
- Number of pole pairs and geometry of the laminated core,
- Copper fill factor and winding design,
- Current carrying capacity,
- Heat dissipation and installation situation.
The copper fill factor describes the proportion of electrically effective copper in the available winding space. A high fill factor means that particularly large amounts of copper can be accommodated within the same motor size. It significantly determines the electrical resistance through the number of windings; in addition, factors such as conductor cross-section, conductor length, number of turns, temperature, and wiring configuration, are also decisive.
Thermal design of a torque motor
The continuously usable torque is significantly limited by the motor temperature and the possible heat dissipation. With a holding torque at zero speed (torque at standstill), electrical power losses continue to occur in the winding, even though no mechanical output power is delivered.
The thermal behavior of an integrated drive therefore depends not only on the motor, but also on stator connection, housing, cooling, load profile, and ambient temperature.
TQ motors are designed for such demanding load conditions. In the ILM series, thermally conductive adhesive and the potting of the stator windings additionally support a good thermal connection to the customer's housing.
FAQs about torque motors
What is a torque motor?
A torque motor is an electric servo motor whose electromagnetic design is optimized for high torque, especially at low to medium speeds. The term describes the operating behavior of the motor and does not automatically refer to its mechanical design. A torque motor can, for example, be designed as a frameless motor, in which the stator and rotor are directly integrated into the surrounding structure.
What is the difference between a torque motor and a frameless motor?
A torque motor describes the electromagnetic design of a motor, while the term “frameless motor” refers to the mechanical design. A frameless motor consists of a separate stator and rotor without its own motor housing. If this motor is also designed for high torque and high torque density, it is a frameless torque motor.
What does torque density mean in a torque motor?
Torque density describes how much torque a motor generates relative to its volume or weight. High torque density enables smaller and lighter drives while still delivering high available torque. This is especially relevant in applications with limited installation space or moving axes, for example in robotics, medical technology, or mobile systems.
What factors influence the torque density of a torque motor?
Torque density is determined by the interaction of several design and electromagnetic factors. These include, among others, the magnetic circuit, number of pole pairs, geometry of the laminated core, copper fill factor, winding design, current-carrying capacity, and heat dissipation. No single factor alone determines torque density. What is decisive is the coordinated design of the entire motor.
What role does the copper fill factor play in a torque motor?
The copper fill factor describes the proportion of electrically effective copper in the available winding space. A high copper fill factor makes it possible to accommodate a large amount of copper within a given motor size. However, electrical resistance is not determined by the copper fill factor alone. It is influenced in particular by the number of turns, conductor length and conductor cross-section, as well as temperature and winding configuration.
Why is thermal management important for torque motors?
The thermal connection influences how much torque a torque motor can provide continuously. Loss heat is generated in the winding and must be dissipated via the stator, housing, and, if applicable, a cooling system. Especially at standstill torque, heat is generated even though no mechanical output power is delivered. Therefore, the motor, installation situation, load profile, and cooling must be considered together.