Complete solution of ETEL TMB+torque motor selection parameters

Selection and parameter interpretation of ETEL TMB+series direct drive torque motor

In the application fields of high-end CNC machine tools, semiconductor manufacturing, robot joints, and precision turntables, direct drive torque motors are gradually replacing traditional "servo motor+decelerator" solutions due to their advantages of zero backlash, high rigidity, high dynamic response, and low maintenance costs. The TMB+series of ETEL (a Swiss company under the Heidelberg Group) is a well-known frameless torque motor product line in the industry, providing a complete selection spectrum from diameters of 0140mm to 1221mm and peak torque from tens of Newton meters to tens of thousands of Newton meters. This article is based on the official technical data manual, systematically interpreting the model system, core performance parameters, thermal management points, and selection methodology of the TMB+series, to help motion control engineers quickly locate suitable motor specifications.

Series Overview and Model Naming Rules

The TMB+series covers a variety of machine base sizes, including 0140, 0175, 0210, 0290, 0291, 0360, 0450, 0530, 0760, 0990, 1221, etc. (numbers usually represent stator outer diameter or series code). Each type of machine base provides multiple voltage/current/torque combinations based on winding design (such as SA, SB, TA, TB, UA, UB, UD, VA, VB, WD, WH, etc.) to meet different bus voltages (standard 600VDC) and application load curves. For example:

TMB+0140-030: A motor with an outer diameter of approximately 140mm, where 030 may represent a certain length or torque level.

TMB+0175-050: outer diameter of approximately 175mm, rated torque of approximately 50Nm level.

TMB+0210-150: The outer diameter is about 210mm, and the peak torque can reach about 200Nm.

TMB+0360-200: outer diameter of approximately 360mm, peak torque exceeding 2900Nm.

TMB+0450-200: Peak torque of over 4800Nm.

TMB+0530-150: Peak torque exceeding 5000Nm.

TMB+0760-150: Peak torque exceeds 11000Nm.

TMB+0990-200: Peak torque exceeds 27000 Nm.

TMB+1221-150: Maximum model with peak torque exceeding 30000 Nm.

Multiple windings are usually provided under each model (such as winding codes: SA, SB, RA, RB, TA, TB, UA, UB, UD, VA, VB, WD, WH, UJ, WT, etc.), and different windings correspond to different torque constants (Kt), back electromotive force constants (Ku), resistance, and inductance, thereby affecting the torque output capability and copper loss at different speeds.

Interpretation of Core Performance Parameters

The technical data sheet is organized into three main sections: Motor Performance, Motor Setting, and Motor Environment.

2.1 Motor performance parameters (dynamic capability)

Peak torque (Tp): The maximum torque that can be output in a short period of time (usually 5% duty cycle), used for acceleration, deceleration, and overcoming instantaneous loads. For example, the SA winding Tp of TMB+0140-030 is 39.6Nm, while the WD winding Tp of TMB+0990-200 exceeds 27000 Nm.

Intermittent torque (Ti): The torque that can be continuously output at a 40% duty cycle, suitable for periodic loads.

Continuous torque (Tc): The torque that can be continuously output under 100% duty cycle and water-cooled conditions (thermal balance). This is the ability boundary of the motor for long-term operation.

Static torque (Ts): The torque that can be continuously output at zero or low speed (without speed limitation, mainly subject to thermal limitation).

Corresponding currents (Ip, Ii, Ic, Is): peak, intermittent, continuous, and static currents (effective value, Arms), respectively. These current values directly determine the selection capacity of the driver.

Maximum speed (nm, nm, FW): The highest speed under conditions of no weak magnetic field and weak magnetic field. Note that weak magnetism can reduce torque capacity, but it can expand the range of constant power speed regulation.

Peak/Intermittent Duration (τ on, p, τ on, i): The maximum time allowed to continuously apply peak/intermittent torque, typically in seconds, used for designing acceleration and deceleration times.

Power loss (Pp, Pi, Pc): Copper loss (winding heating) corresponding to current, is an important input for thermal management.

2.2 Motor Setting Parameters (Electrical/Mechanical Characteristics)

Torque constant Kt (Nm/Arms): The torque generated per unit current is the most critical parameter for selecting windings. High Kt means greater torque at the same current, but also higher back electromotive force, limiting high-speed performance.

Back electromotive force constant Ku (Vrms/(rad/s)): The voltage generated per unit speed directly affects the driver voltage margin and weak magnetic control strategy.

Motor constant Km (Nm/√ W): an indicator for measuring the electromagnetic efficiency of a motor, Km = Kt / √R， The larger the value, the stronger the torque output capability under the same copper loss.

Phase resistance R20 (Ω): The DC resistance at 20 ℃ affects copper loss (I ² R) and increases with temperature (temperature coefficient of copper resistance is about 0.4%/K).

Phase inductance Ld/Lq (mH): Direct and quadrature axis inductance, affecting current rise rate and high-speed performance.

Maximum short-circuit current Isc (Arms): The current generated when a motor terminal is short circuited, used for fault analysis.

Base speed nb (rpm): The highest speed (inflection point speed) at which the rated torque is reached under the rated bus voltage.

Rated operating point (nn, Tn, In): the speed, torque, and current under typical continuous working conditions.

Thermal time constant τ th (s): The temperature rise response time constant used to estimate the cooling time after overload.

Thermal resistance Rth (K/W): The thermal resistance from the winding to the cooling water determines the temperature rise (Δ T=P × Rth).

Pole pair 2p: affects the control parameters of the driver.

Rotor inertia J (kg · m ²): used to calculate acceleration and deceleration time and dynamic response.

Rotor mass mr and stator mass ms (kg): used for structural design.

2.3 Motor environmental parameters (cooling and working conditions)

Nominal DC bus voltage Udc: typically 600VDC.

Intermittent/peak duty cycle Di, Dp: The standard is 40% and 5%, which can be adjusted according to the application (thermal load needs to be re evaluated).

Cooling water parameters: inlet water temperature θ w (20 ℃), allowable temperature rise Δ θ w (5 ℃ or 10 ℃), minimum water flow rate qw (l/min), maximum pressure drop Δ pw (bar). Water cooling is the key to maintaining continuous torque in high-performance motors, and sufficient flow and pressure must be provided according to manual requirements.

Requirements for Thermal Management and Cooling Systems

The thermal management of torque motors directly determines their actual continuous output capability. The manual clearly provides data based on water cooling, and all torque values (Tc, Ti, etc.) depend on specified cooling conditions (inlet water at 20 ℃, water flow rate meets requirements). If the cooling is insufficient, the actual continuous torque must be reduced.

The thermal resistance Rth is usually between 0.005~0.1 K/W, which means that every 1 W of copper loss will cause a temperature rise of several tens of mK. For example, with Rth ≈ 0.16 K/W and continuous loss Pc ≈ 650W for TMB+0140-030, the winding temperature rise is about 104K (approximately 124 ℃ relative to the inlet water temperature of 20 ℃), which is close to the maximum allowable temperature of 130 ℃, indicating a compact design.

The minimum water flow rate varies from 2 l/min (for small motors) to about 40 l/min (for large motors), and the pressure drop can reach several bars as the flow rate and internal waterway structure increase. Clean cooling water (rust proof, algae proof) must be used in the project, and temperature and flow rate must be monitored.

Selection process and precautions

Step 1: Determine the load curve

Calculate the torque speed time curve in applications, including acceleration torque, uniform torque, deceleration torque, and static torque. Pay attention to inertial loads and friction torque.

Step 2: Evaluate the heat load

Calculate the equivalent root mean square torque (rms) based on the cycle time and convert it to the equivalent root mean square current. Ensure that the current is less than the continuous rated current (Ic) of the motor, and the peak current does not exceed Ip. At the same time, check whether the peak and intermittent time are within the limits of τ on, p/τ on, i.

4.3 Step 3: Select winding

Calculate the upper limit of the required back electromotive force coefficient based on the maximum required speed and available bus voltage; Select the appropriate winding for Kt based on the required torque and current limitations. General rule: Low Kt winding (high speed) can provide higher speed but lower torque at the same current; High Kt winding (high torque) has good low-speed performance but limited high-speed performance. You can refer to the "base speed" indicator in the manual.

Step 4: Verify cooling conditions

Confirm the available cooling water flow rate and temperature on site, and compare them with the minimum flow rate and pressure drop requirements in the manual. If an external water chiller is used, it is necessary to ensure that the heat dissipation power is greater than Pc (continuous loss) and leave redundancy.

Step 5: Dimensions and Mechanical Interfaces

Check the outer diameter, length, and installation hole position of the rotor/stator to ensure compatibility with the mechanical design. At the same time, pay attention to the influence of rotor inertia on system resonance, and if necessary, add filters or adjust control parameters.

Safety and usage restrictions

The manual clearly warns that any use beyond speed/torque limits may result in dangerous voltage and serious injury. Users must set software or hardware limits themselves to ensure that the motor always operates in the safe operating area (SOA). ETEL does not assume any responsibility for improper use.

In addition, the temperature of the motor winding should not exceed 130 ℃. It is recommended to integrate temperature sensors (such as PTC or KTY) in the control system for real-time monitoring. After short-term overload, sufficient cooling time (about 3-5 times the thermal time constant) should be left to restore thermal equilibrium.