Bonfiglioli BMD Servo Motor Selection and Configuration Guide

Bonfiglioli BMD Series Permanent Magnet Synchronous Servo Motor: Selection and Feedback System Configuration Guide

In the field of modern industrial automation, the performance bottleneck of servo systems often lies not in the controller, but in the matching degree between the motor and the feedback system at the execution end. Bonfiglioli's BMD Series permanent magnet AC synchronous servo motor, with its high neodymium magnet (NdFeB) rotor and compact mechanical design, provides a high dynamic response drive core for industries such as woodworking, metalworking, packaging, robotics, and food and beverage. However, to truly unleash the performance potential of BMD motors, engineers must make precise decisions in the selection, feedback configuration, and wiring stages. This article will provide you with a complete guide from theoretical calculations to engineering implementation based on the core technical parameters of the BMD series.

Understand the core advantages of the BMD platform

It is crucial to understand the design philosophy of the BMD platform before delving into the selection process. This series covers six machine base sizes from BMD 65 to BMD 170, providing a range of locked rotor torque from 0.85 Nm to 45 Nm (naturally cooled) and up to 60 Nm (forced air cooled).

Its core advantages lie in extremely low rotor inertia and high overload capacity. Thanks to the neodymium magnet material, BMD motors can withstand instantaneous peak torque (usually three times the locked rotor torque) without the risk of demagnetization. This characteristic makes it particularly suitable for cyclic operating conditions that require frequent start stop and rapid acceleration/deceleration (Duty type S3).

In addition, the protection level of BMD motors comes standard with IP65 and can be optionally IP67. Coupled with an F-class insulation system, it has strong survivability in harsh environments such as dust and humidity.

Engineering calculation steps for servo motor selection

The correct selection begins with precise calculations. According to the guidelines on page 11 of the manual, selection should take into account both thermal equivalent torque and speed limitations.

1. Equivalent torque calculation（MEQU）

In actual working conditions, the motor does not operate at constant torque. The first step in selection is to calculate the equivalent torque within one working cycle, ensuring that the value is lower than the rated torque of the motor（Mn）. The calculation formula is as follows:

MEQU=M one two⋅tone+

M two two⋅t two+⋯+Mn two⋅tn t one+t two+⋯+tn

Torque at each stage ti

Duration of each stage

The core logic of this calculation is to convert a non constant load into an equivalent constant load for verifying the thermal capacity of the motor. If the equivalent torque exceeds the rated torque of motor S1 under the working system, larger motor specifications or the addition of forced ventilation option (IC416) need to be considered.

2. Temperature correction and speed boundary

Pages 8-9 of the manual define the concept of thermal equilibrium: a state where the rate of temperature change is less than 1K/half hour. Attention should be paid when selecting:

Environmental temperature correction coefficient（ft）When the ambient temperature exceeds the standard operating condition of 40 ℃, the continuous output torque of the motor needs to be reduced according to the curve on page 11 of the manual.

Voltage limit curve: The continuous working area (S1) of the motor is enclosed by the "maximum continuous torque curve" and the "voltage limit curve". The voltage limit is determined by the rated speed of the motor（nn）Decided. The manual clearly states on page 40 that the voltage limit is usually much lower than the mechanical limit speed. When selecting, the voltage limit curve should be chosen to cover the motor with the highest application speed, in order to avoid the driver entering the weak magnetic zone and causing a decrease in efficiency.

Deep analysis and selection of feedback system

A major highlight of the BMD series is the provision of a wide range of feedback options, from highly robust rotary transformers (Resolvers) to high-precision encoders that support Functional Safety. The manual provides detailed explanations on pages 13-15 and 48-51.

1. Parser: A classic choice for high reliability

Model: RES1 (8kHz) and RES2 (10kHz)

Applicable scenarios: environments with high vibration, high temperature, and severe oil pollution (such as injection molding machines and metal cutting machines).

Key parameters: Extreme logarithm of 2, accuracy error of ± 10 '. Its output is an analog sine cosine signal, and the resolution depends on the analog-to-digital converter (ADC) of the driver. The technical parameter table on page 49 of the manual shows that its operating temperature can reach -55 ℃ to+155 ℃, far exceeding that of optical encoders.

2. Optical Absolute Encoders

The BMD series is compatible with high-end optical encoders from Heidenhain and SICK:

Heidenhain ECN/EQN series (ENB1/ENB2): Supports EnDat 2.2 protocol, providing up to 13 bit/turn single turn resolution and 12 bit multi turn counting. Machine tool pivot axis suitable for high-precision positioning.