Bonfiglioli BTD/BCR Synchronous Servo Motor Selection and Interface Configuration Guide

Bonfiglioli Vectron BTD/BCR synchronous servo motor: professional selection and technical characteristics

In the field of modern industrial automation, the requirements for dynamic response, accuracy, and efficiency of motion control systems are becoming increasingly stringent. Bonfiglioli Vectron's BTD and BCR series permanent magnet synchronous servo motors provide high-performance drive solutions for industries such as packaging, textiles, machine tools, robots, and material handling, thanks to their optimized magnetic circuit design, compact structure, and rich feedback options. This article aims to provide engineers with a detailed technical reference, covering the technical differences between two series, key selection parameters, mechanical interface specifications, and feedback system configurations.

BTD and BCR series: Technical positioning and core differences

The Bonfiglioli Vectron servo motor series covers a wide range of application needs through two different technological paths.

BCR series (Brushless Classic Range): This series adopts standard wound stator technology, emphasizing high dynamic response and large torque range. Its continuous stalling torque covers 0.2 Nm to 115 Nm and has an instantaneous overload capacity of up to 400%. This makes the BCR series very suitable for applications that require frequent start stop, rapid acceleration and deceleration, and the ability to withstand impact loads, such as robot joints, high dynamic packaging lines, and metal cutting machines.

BTD series (Brushless Torque Density): This series adopts advanced winding magnetic pole technology, with core advantages of high torque density (up to 16 Nm/dm ³) and compact volume. Under the same torque output, the installation space of BTD motor is smaller. Its torque density range is approximately 3.4 to 5.6 Nm/dm ³, making it particularly suitable for applications with limited installation space but high torque output requirements, such as precision electronic manufacturing equipment and compact automation units.

Selection decision point: If the main challenge of the application is space limitation, prioritize the BTD series; If the main challenges are extreme overload and dynamic response, the BCR series is a more suitable choice.

Interpretation and selection calculation of key technical parameters

A correct understanding of motor parameters is the foundation for ensuring system performance matching.

1. Stuck torque (M ₀) and rated torque (M ₙ)

Locking torque (M ₀): The maximum torque that the motor can continuously output at zero speed, which is the primary reference value for selection.

Rated torque (M ₙ): The torque that the motor can continuously output at rated speed. Usually M ₙ is slightly smaller than M ₀.

Selection rule: The continuous torque required for the application (including safety factor) should be less than or equal to the rated torque of the motor (M ₙ). For periodic loads, it is necessary to calculate the effective torque (RMS torque) to ensure that it is less than M ₙ.

2. Torque constant (K ₜ) and back electromotive force constant (K ₑ)

Torque constant (K ₜ, Nm/A): represents the torque that the motor can generate per ampere of current. The larger the K ₜ value, the greater the torque generated under the same current.

Reverse electromotive force constant (K ₑ, V/1000 min ⁻¹): represents the reverse voltage generated by the motor every 1000 revolutions. K ₑ determines the driving voltage required by the motor at a specific speed.

Relationship: Under the SI unit system, K ₜ (Nm/A) ≈ K ₑ (V/(rad/s)). But the K ₑ unit in the manual is V/1000min ⁻¹, so when converting, attention should be paid to the unit conversion (1 V/1000min ⁻¹ ≈ 0.00955 V/(rad/s)).

3. Moment of inertia (J ₘ) and mechanical time constant (τₘₑ c)

Moment of inertia (J ₘ, kgcm ²): affects the acceleration capability of the system. The ratio of load inertia to motor inertia (inertia ratio) is a key parameter that determines the response speed and stability of the system. The recommended inertia ratio for high dynamic applications is ≤ 5:1.

Mechanical time constant (τₘₑ c, ms): represents the theoretical time required for the motor to accelerate from zero to rated speed. The smaller the τₘₑ c, the faster the dynamic response of the motor. From the data, it can be seen that due to optimized rotor inertia design, the mechanical time constant of the BTD series is usually smaller than the BCR of the same aircraft number (such as BTD5 being 0.4-0.7ms and BCR5 being 0.7-1.4ms), indicating that BTD has faster acceleration capability.

Mechanical interface and installation specifications

The BTD and BCR series use standardized mechanical interfaces to facilitate coupling with gearboxes or other transmission components.

1. Flanges and shaft extensions

According to the motor size (Size 2 to 8), different flange interfaces (IMB table) have been defined. Taking standard configuration as an example:

BTD2/BCR2: Shaft diameter D=9 mm, shaft length E=21.5 mm, flange stop A=40 mm, installation hole spacing B=63 mm.

BTD4/BCR4: Shaft diameter D=24 mm, shaft length E=46.5 mm, flange stop A=130 mm, installation hole spacing B=165 mm.