Technology

The EJ7411 EtherCAT plug-in module integrates a full-fledged amplifier for Brushless DC motors/Electric commutation motor, or BLDC motor/EC motor for short.

Although the name would suggest otherwise, this motor does not resemble a conventional single-phase DC motor, but rather a three-phase permanently excited synchronous or servomotor. Both are three-phase motors whose windings are operated with a 120° phase shift.

• The differences in the interior structure are the slightly deviating windings.
• A servomotor has a sinusoidal counter-electromotive force, while that of a BLDC motor is trapezoidal.
• One clearly visible difference is the design. BLDC motors often have a much lower axial height, allowing them to be used in machines where installation space is limited.
• In addition, they often only have wires fed to the outside and no connector for the connection of a motor cable.
• Also, these motors normally have no high-resolution feedback installed, but are mostly commutated and operated with integrated Hall sensors or an incremental encoder mounted on the motor shaft.

Due to the points listed, BLDC motors are in most cases cheaper than servomotors.

The BLDC motor and the EJ7411 amplifier output stage together form the drive. The BLDC motor is operated in a closed control loop, with position, velocity or torque control.