Summary of An Introduction to Brushless DC Motor Control
This article outlines the fundamentals of Brushless DC (BLDC) motors, highlighting their advantages over traditional brushed motors, such as increased reliability, reduced size, and higher efficiency due to the elimination of mechanical commutators. It explains that BLDC motors require electronic management via microcontrollers and sensors for precise timing and control. The text specifically focuses on three-phase units, describing their stator construction and synchronous operation without slip.
Parts used in the BLDC Motor Project:
- Brushless DC motor
- Electronic commutator
- Microcontroller
- Sensors
- Stator coils
- Rotor
- Steel laminations
- Windings
The brushless DC (BLDC) motor is becoming increasingly popular in sectors such as automotive (particularly electric vehicles (EV)), HVAC, white goods and industrial because it does away with the mechanical commutator used in traditional motors, replacing it with an electronic device that improves the reliability and durability of the unit.
Another advantage of a BLDC motor is that it can be made smaller and lighter than a brush type with the same power output, making the former suitable for applications where space is tight.
The downside is that BLDC motors do need electronic management to run. For example, a microcontroller – using input from sensors indicating the position of the rotor – is needed to energize the stator coils at the correct moment. Precise timing allows for accurate speed and torque control, as well as ensuring the motor runs at peak efficiency.
This article explains the fundamentals of BLDC motor operation and describes typical control circuit for the operation of a three-phase unit. The article also considers some of the integrated modules – that the designer can select to ease the circuit design – which are specifically designed for BLDC motor control.
The advantages of brushless operation
The brushes of a conventional motor transmit power to the rotor windings which, when energized, turn in a fixed magnetic field. Friction between the stationary brushes and a rotating metal contact on the spinning rotor causes wear. In addition, power can be lost due to poor brush to metal contact and arcing.
Because a BLDC motor dispenses with the brushes – instead employing an “electronic commutator” – the motor’s reliability and efficiency is improved by eliminating this source of wear and power loss. In addition, BLDC motors boast a number of other advantages over brush DC motors and induction motors, including better speed versus torque characteristics; faster dynamic response; noiseless operation; and higher speed ranges.1
Moreover, the ratio of torque delivered relative to the motor’s size is higher, making it a good choice for applications such as washing machines and EVs, where high power is needed but compactness and lightness are critical factors. (However, it should be noted that brush-type DC motors do have a higher starting torque.)
A BLDC motor is known as a “synchronous” type because the magnetic field generated by the stator and the rotor revolve at the same frequency. One benefit of this arrangement is that BLDC motors do not experience the “slip” typical of induction motors.
While the motors can come in one-, two-, or three-phase types, the latter is the most common type and is the version that will be discussed here.
The stator of a BLDC motor comprises steel laminations, slotted axially to accommodate an even number of windings along the inner periphery (Figure 1). While the BLDC motor stator resembles that of an induction motor, the windings are distributed differently.
For more detail: An Introduction to Brushless DC Motor Control
- Why are BLDC motors becoming popular in automotive and HVAC sectors?
They eliminate the mechanical commutator, which improves reliability and durability. - Can a BLDC motor be made smaller than a brush type with the same power output?
Yes, they can be made smaller and lighter while maintaining the same power output. - What is required to run a BLDC motor?
Electronic management is needed, including a microcontroller and position sensors. - How does the microcontroller contribute to motor performance?
It energizes stator coils at the correct moment to ensure accurate speed, torque control, and peak efficiency. - What are the specific advantages of brushless operation compared to brushed motors?
Advantages include better speed versus torque characteristics, faster dynamic response, noiseless operation, and higher speed ranges. - Does a BLDC motor experience slip like an induction motor?
No, because it is a synchronous type where the stator and rotor magnetic fields revolve at the same frequency. - Which phase type of BLDC motor is the most common?
The three-phase type is the most common version discussed in the article. - What component makes up the stator of a BLDC motor?
The stator comprises steel laminations slotted axially to accommodate windings along the inner periphery.
