A controller, why?*

Need for a controller to drive a BLDC motor

The BLDC (Brushless DC) and PMSM (Permanent Magnet Synchronous Motors) are now ubiquitous in modern applications: electric vehicles, robots, agricultural machinery, industrial automation, etc.

But unlike a conventional DC motor, these motors cannot operate directly under a DC voltage.

They require an electronic controller, also known as an inverter, to ensure their precise and safe operation.

From DC to three-phase AC

A BLDC motor is powered by 48–51.2 V DC (often via a lithium LFP or NMC battery pack).

However, its operation relies on alternating phases (AC), which must be switched in synchronisation with the rotor position.

The controller plays an essential role here:

• It converts the direct current (DC) from the battery into three-phase alternating currents (AC) suitable for the motor.

• It synchronises the phase switching with the rotor position, measured by a Hall sensor, an encoder, or estimated via a sensorless algorithm.

Without this controller, the motor could neither start nor maintain stable rotation.

Control of torque, speed, and ramps

The controller is not just a simple inverter: it is a true dynamic regulation unit.

It adjusts in real-time:

• The current in the windings → this current is directly proportional to the motor torque.

• The rotational speed → via modulation of the average applied voltage.

• The acceleration and deceleration ramps → to ensure smooth transitions and avoid mechanical jolts.

Thanks to this fine management, the controller enables smooth, silent, and precise operation, essential for mobile, robotic, or agricultural applications.

Integrated protection and safety

Modern controllers integrate numerous electronic protections designed to safeguard both the motor and the battery:

• Overvoltage / Undervoltage: automatic shutdown in case of an anomaly on the power line.

• Overcurrent: limitation or shutdown to prevent destruction of transistors or windings.

• Overheating: automatic reduction of torque or safety shutdown.

• Sensor error / rotor lock: rapid detection of a synchronisation fault.

These functions prevent costly damage and increase the overall system lifespan.

Data and supervision

BLDC/PMSM motor controllers are not limited to control: they also play a key role in supervision and predictive maintenance.

They measure and communicate essential parameters such as:

• Instantaneous current (effort or motor torque)

• Rotational speed

• Motor or electronic temperature

• Supply voltage

• Fault codes and error histories

These data are accessible via communication interfaces (CAN, RS485, PWM, I/O) and allow direct integration into an embedded system, a PLC, or a supervisor.

A central element of robotisation

In modern architectures, the controller becomes the local brain of the motor.

It ensures energy conversion, dynamic regulation, and communication with the upper system (computer, PLC, main controller).

It is indispensable for achieving:

• Precise and repeatable movements,

• Coordinated multi-axis control,

• Maximum energy efficiency,

• And integrated safety close to the action.

In summary

Conclusion

The BLDC motor controller is much more than a mere accessory: it is a vital component of the system.

Without it, it is impossible to convert DC energy into useful motion, ensure motor safety, or exploit the full potential of modern drives.

It is the intelligent link between the battery, the motor, and the brain of the machine.

*: The technical information presented in this article is provided for informational purposes only. It does not replace the official manuals of the manufacturers. Before any installation, handling, or use, please consult the product documentation and adhere to safety instructions. Torque.works cannot be held responsible for inappropriate use or incorrect interpretation of the information provided.