Complete solution of ETEL TMB+torque motor selection parameters

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.