REXRTOH MDD Digital AC Servo Motor Application Guide

REXRTOH MDD Digital AC Servo Motor Application Guide

Overview and Product Positioning

The MDD series digital AC servo motor is a high-performance permanent magnet synchronous motor launched by INDRA MAT GmbH (later merged into Indramat) in Germany. It adopts electronic commutation technology and has high dynamic response, high power density, and high-precision control characteristics. This series of motors is designed specifically for industrial automation systems, especially suitable for applications that require high-speed and high-precision contour control, such as tool machines, textile machinery, printing equipment, packaging machinery, robots, and handling systems. The MDD motor, when used in conjunction with the Indramat intelligent digital drive controller, creates a responsive and cost-effective automation solution.

The MDD series includes nine different models, covering a full range of requirements from low inertia and low torque to high torque and high dynamics. among which

MDD 021、 025, 041: Compact structure, high power density, suitable for tightening devices, auxiliary shafts, and tool changing mechanisms;

MDD 065、 071, 093, 115: Excellent dynamic performance, suitable for high dynamic scenarios such as stamping, punching, and step-by-step feeding;

MDD 090、 112: Extremely high synchronization performance, suitable for precision machining operations such as grinding machines that require high synchronization.

Motor structure and core technology

2.1 Structural Features

The MDD motor adopts a brushless design, and the rotor is made of rare earth or ferrite permanent magnet materials to achieve low rotational inertia. The motor casing is fully enclosed, and both the power supply and feedback interfaces meet the IP65 protection level, allowing it to operate directly in harsh environments such as coolant or emulsion environments. The motor is equipped with a built-in temperature sensor (PTC) to monitor the winding temperature in real-time and prevent overheating and damage.

2.2 Performance advantages

High dynamism: excellent torque inertia ratio, rapid response;

High overload capacity: high-efficiency thermal conductivity design from stator winding to shell;

Wide speed range peak torque: peak torque can be output over a wide range of speeds;

High power to weight ratio: compact structure, high power density;

High cyclic load capacity: supports high-frequency start stop operations;

High synchronization performance: using sine current drive and high-resolution motor feedback system.

2.3 Installation and Connection

The motor supports multiple installation directions, and the flange complies with IM B5 (through-hole) or IM B14 (threaded hole) standards. The output shaft can be selected as the optical axis (recommended) or a keyway shaft. The power supply and feedback cables are directly connected through connectors, and support customization of lateral A/B or left/right output directions.

Analysis of key technical parameters

3.1 Environmental conditions

Environmental temperature: 0 ° C to+45 ° C

Installation altitude: 0-1000 meters

Protection level: IP65 (motor body), the output shaft may be IP50 or IP65 depending on the model

Mechanical environment: compliant with IEC 721-3-3 standard, suitable for 3M1 (longitudinal) and 3M6 (transverse) vibration levels

3.2 Motor Feedback System

MDD motors come standard with a high-precision feedback system, which is divided into:

Resolver Feedback (RSF): Inductive system, resolution 16384 increments/rev, system accuracy ± 7 arcminutes;

Digital Servo Feedback (DSF): Optical system, resolution 2097152 increments/rev, system accuracy ± 0.5 arcminutes.

Both types of feedback support relative position detection and absolute position detection (integrated multi turn absolute value encoder). The absolute position information can still be maintained after power failure without the need to reset to zero.

3.3 Torque speed characteristics

The torque speed curve is the core basis for selection, and the figure includes:

Maximum torque limit (horizontal line)

Speed limit (affected by DC bus voltage)

S1 continuous working curve (natural cooling or surface cooling)

S6 intermittent working curve (duty cycle 25%)

The curve varies depending on the type of power source (regulated/non regulated) and voltage fluctuation (± 10%), and the selection should be based on actual operating conditions.

3.4 Axle Load Capacity

The motor shaft can withstand radial and axial loads, and the radial force chart displays the relationship between the allowable value and the distance from the point of application, as well as the average speed. The formula for calculating axial force is:

F-axis=k ⋅ F-radial

The value of k varies depending on the model (e.g. MDD 021 is 0.60, MDD 041 is 0.53). The rated life of the bearing is 30000 hours, and the life decreases in cubic terms when overloaded.

Overview of detailed technical data for each model

MDD 021

Continuous torque: 0.15-0.30 Nm

Maximum torque: 0.64-1.3 Nm

Rated speed: 10000 rpm

Moment of inertia: 0.22-0.31 × 10 ⁻⁴ kg · m ²

Protection: IP65 (main body), IP50 (shaft)

MDD 025

Continuous torque: 0.33-0.90 Nm (slightly reduced with braking)