Brushless motors in automation

There is great fanfare of excitement in brushless motors, so what is special about this technology?

A brushless motor has its roots in 3 phase motors. In both motors, the order and frequency of energising of three coils determines the direction and speed of rotation. A brushless motor combines the high start up torque of a DC brush motor without the life limiting wearing of carbon brushes.

Brushless motor development was accelerated by their application in robotics where precise positioning and control at very low speeds requires very special control techniques. Now the technology is widespread and more affordable, the benefits are spreading into gate and barrier automation.

In the past, to get from point A to point B, you would apply power and monitor the progress of movement through an incremental encoder. The controller would run the motor until it had received the correct number of pulses back from the encoder. Feedback was necessary because motor speed was load dependant, so time was not an accurate predictor of position.

Much higher speeds and 24 accurate shaft positions per revolution allow a gearmotor to accurately run from A to B over thousands of individual steps. There is no need for an encoder to monitor that progress.

Of course, this requires a much more complex controller running 3 of more coils in a precise sequence. The cost and reliability of today’s automation systems rests in their control panels. High power dedicated control chips will eventually bring down price and improve reliability.

Proponents of brushless automation point out the higher efficiency and silent operation. Controlled acceleration leads to lower power motors being required (who needs a 300hp hatchback). As for silence, no car park barrier has ever kept me awake at night.

Manufacturer’s drive for efficiency pays homage to the European Energy Directive. But a barrier that operates 200 times a day only runs for 2% of the day.

In conclusion, the demands of gate and barrier automation do not need this advanced technology, but the industry will benefit from new products that we will pay a premium for.