Motors are perhaps the most important invention ever. They make things go around, they make things move, and that makes life happen as we know it. Up until recently, brushed DC motors were used pretty much everywhere. However, we now have another type of motor, called brushless DC, or BLDC motors. In layman terms, a brushless DC motor is an electronically commuted DC motor which doesn’t have brushes.
Now, his fundamental difference in structure as compared to a brushed DC motor provides certain advantages to BLDC motors and also makes them a bit tricky to operate. In this article, we’re going to take a look at these motors and find out all about them.
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What are BLDC motors?
Aforementioned, BLDC or Brushless DC motors are electronically commuted DC motors without brushes. These motors work with a controller providing a pulse of current to the motor windings that control the speed and torque of the synchronous motor.
These motors are highly efficient in producing a large amount of torque over a vast speed range. To solve the problem of connecting current to the armature, permanent magnets rotate around a fixed armature instead.
They are known primarily for smooth functioning and holding torque when stationary. There are two major types of BLDC motors. The difference is only structural, though, the fundamental working principle remains the same:
- Outer Rotor: Also called outrunner motors sometimes. The winding is inside the core of the motor surrounded by rotors. They operate at lower currents and have low cogging torques. Most commonly seen in DIY quadcopters.
- Inner Rotor: The exact opposite of outrunner motors. The rotor is in the core surrounded by the motor windings. Due to this, it produces a tremendous amount of torque.
How do they work?
The working principle of both brushed and brushless DC motors is the same — internal shaft position feedback.
A BLDC has only two basic parts — the rotor and the stator. The rotor, as you’d guess, is the rotating part and the stator the stationary part. Permanent magnets are attached to the rotor and electromagnets to the stator. High-power transistors are used to activate the electromagnets in order to turn the shaft. The power is controlled by a controller that uses solid-state circuitry to perform power distribution.
Advantages of BLDC motors
BLDC motors have distinct benefits in a lot of applications over traditional brushed DC motors:
- Higher efficiency
- Can operate at higher RPMs without any issues and under any condition
- Accelerate/decelerate efficiently as they have low rotor inertia
- The absence of brushes means higher reliability and lower maintenance
Nothing comes without its set of disadvantages though. Same goes for BLDCs:
- They cost way more than their brushed counterparts
- Limited high power can be applied to BLDC motors. Otherwise, too much operational heat might damage the magnets and motor winding inside.
BLDC motors are, no doubt the next step forward in what is perhaps the most crucial component for the future. When planning for your next build, be sure to keep these pointers in mind and pick the right motor.
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