Sensored & Sensorless BLDC Motors Mean Longer Life & Lower Maintenance

Sinotech    November 18, 2014

BLDC Motors ConsttructionBLDC motors, or brushless DC motors, have similar speed performance and torque as brushed motors. Their increasing popularity keeps BLDC motor suppliers busy because of the various benefits that they offer over their brush-type counter parts. Among brushless DC motors are those with and without sensors.

Benefits of BLDC Motors

The elimination of brushes for commutation in DC motors makes them:

  • Simpler to maintain
  • More efficient
  • Less noisy
  • Cooler in temperature
  • Have a life expectancy of up to 10,000 hours or more

While the initial cost of a BLDC motor may be more than a brushed motor, its efficiency and longevity easily offsets the cost.

Sensored BLDC Motors

Sensored brushless motors use a Hall effect sensor. The transducer varies the output voltage based on the magnetic field. This type of motor is good for positioning, proximity switching, sensing applications and speed detection because the motor system knows the position of the rotor. This is important at low speeds and during the start phase, when the rotor doesn’t move, so the speed-controlling mechanism applies power to the correct rotor phase combination.

After gathering information from the transmitter’s throttle signal when the rotor is still, the sensored brushless motor acts like a brushed motor. While the motor delivers the maximum torque at zero speed, it doesn’t experience losses regards to the brushes and commutator. Additionally, in a sensor-based design, the speed control and motor are always in accord, regardless of the speed.

Sensorless Brushless DC Motors

In sensorless-based motor design, the speed control doesn’t know the rotor’s position until it’s already spinning and generating a detectable back-electromagnetic field. Sensorless motors use a ramp-up method that applies power to two individual phase coils to determine the position within a stator flux. The motor’s speed and coil energizing pattern power the motor’s phases. Gradually increasing or decreasing the commutation period affects the motor’s speed.

Since motor performance depends on factors such as the stator design, magnet, air gaps and copper content, the type of sensing design does not affect top RPM or power output. While sensored motors aren’t necessarily better than those with a sensorless design, one may be better for your application than another. BLDC motor suppliers like Sinotech can help you determine which is best for yours. Contact Sinotech today to discuss your needs.

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