Brushless DC Motor, How it works ?

Lesics

13 Oct 201404:39

Summary

TLDRThe video script provides an insightful look into the workings of Brushless DC (BLDC) motors, highlighting their advantages over traditional brushed motors in terms of reliability, efficiency, and noise reduction. BLDC motors are favored for their lighter weight and lack of wear-prone brushes that can cause sparking in conventional motors. The operation of a BLDC motor is explained through the interaction between a permanent magnet rotor and an electromagnet stator, with the process likened to a donkey chasing a carrot that perpetually moves out of reach. The script also addresses the power output limitation due to only one coil being energized at a time and explains how this is overcome by energizing a second coil to push the rotor, thus increasing torque and power output. The BLDC's constant torque nature is attributed to this configuration. The use of an electronic controller and a Hall effect sensor to determine rotor position and control coil energizing for continuous rotation is also discussed. The video concludes by differentiating between the outrunner and inrunner BLDC designs, offering viewers a comprehensive introduction to BLDC motors.

Takeaways

🚀 **Reliability & Efficiency**: Brushless DC (BLDC) motors are preferred for their reliability, efficiency, and lower noise levels compared to brushed motors.
🏋️ **Lighter Weight**: BLDC motors are lighter than brushed motors with the same power output, which can be beneficial for applications where weight is a concern.
🔋 **Long Life**: Conventional brushed motors have brushes that wear out and can cause sparking, making them unsuitable for applications requiring long life and high reliability.
🧲 **Permanent Magnet Rotor**: The rotor in a BLDC motor is a permanent magnet, which interacts with the electromagnets created by the energized stator coils.
🌀 **Electromagnetic Interaction**: BLDC motor operation is based on the force interaction between the permanent magnet and the electromagnets in the stator.
🔄 **Sequential Activation**: In BLDC motors, coils are sequentially energized, causing the rotor to rotate as each coil's magnetic field interacts with the rotor's magnetic field.
🥕 **Humorous Analogy**: The operation of a BLDC motor can be remembered like the story of a donkey chasing a carrot that keeps moving out of reach.
🔌 **Single Coil Limitation**: At any given moment, only one coil in a BLDC motor is energized, which can limit the power output.
🤹 **Torque Boost**: By energizing a second coil with the same polarity while the rotor is near the first coil, the motor can produce more torque and power output.
⚙️ **Constant Torque Nature**: BLDC motors have a constant torque nature due to the combined effect of the pushing and pulling forces from the stator coils.
🔄 **Simplified Stator Coil**: A small modification to the stator coil, connecting one free end of the coils together, simplifies the process of energizing two coils separately.
📡 **Electronic Controllers**: BLDC motors use electronic controllers with sensors, often Hall effect sensors, to determine the rotor's position and decide which coils to energize for continuous rotation.
🔍 **Outrunner vs Inrunner**: There are different BLDC motor designs available, such as the outrunner and inrunner types, each with their specific applications.

Q & A

Why are brushless DC (BLDC) motors considered more reliable and efficient than brushed DC motors?
-Brushless DC motors are more reliable and efficient because they do not have brushes that wear out over time and cause sparking, which can lead to reduced performance and shorter lifespan in brushed DC motors.
How does the weight of a BLDC motor compare to a brushed motor with the same power output?
-BLDC motors are lighter than brushed motors with the same power output, making them more suitable for applications where weight is a critical factor.
What is the fundamental working principle behind a BLDC motor?
-The operation of a BLDC motor is based on the force interaction between a permanent magnet (rotor) and an electromagnet (stator coil). When a DC power is applied to the coil, it energizes and attracts the opposite poles on the rotor, causing rotation.
How does the energizing sequence of the stator coils in a BLDC motor contribute to the rotor's continuous rotation?
-The stator coils are energized in a specific sequence as the rotor passes each coil. This sequential energizing creates a rotating magnetic field that keeps the rotor spinning continuously.
What is the humorous analogy used to help remember the BLDC operation?
-The humorous analogy is the story of the donkey and the carrot, where the donkey tries to reach the carrot that keeps moving out of reach, similar to how the BLDC motor's rotor continuously rotates as the magnetic field changes.
What is the drawback mentioned about BLDC motors when only one coil is energized at any instant?
-The drawback is that the two non-energized or 'dead' coils reduce the power output of the motor, as only one coil is contributing to the torque at any given time.
How can the power output and torque of a BLDC motor be improved?
-The power output and torque can be improved by energizing a second coil behind the first one with the same polarity current, which pushes the rotor and produces more torque.
What is the significance of a BLDC motor having a constant torque nature?
-A constant torque nature means that the BLDC motor can maintain a consistent output of torque regardless of changes in speed, which is beneficial for operations that require a steady and reliable power delivery.
How can the process of energizing two coils separately in a BLDC motor be simplified?
-By connecting one free end of the coils together, the process is simplified, allowing power to be applied between two coils, which then distribute the current as needed for the motor's operation.
What role does an electronic controller play in the operation of a BLDC motor?
-An electronic controller uses a sensor, often a Hall effect sensor, to determine the rotor's position and decides which stator coils to energize, ensuring continuous and efficient rotation of the rotor.
What are the two main types of BLDC motor designs mentioned in the script?
-The two main types of BLDC motor designs mentioned are the outrunner type and the inrunner type.
Why are BLDC motors preferred for applications demanding long life and reliability?
-BLDC motors are preferred for such applications because they lack the wear-prone brushes found in conventional DC motors, offer higher efficiency, and provide a longer lifespan with reduced maintenance needs.

Outlines

00:00

🚀 Introduction to Brushless DC Motors

This paragraph introduces the trend towards using brushless DC (BLDC) motors for their reliability, efficiency, and noise reduction compared to traditional brushed motors. It highlights the lighter weight of BLDC motors and the issues with conventional motors, such as brush wear and sparking, which make them unsuitable for operations requiring long life and high reliability. The explanation of how a BLDC motor operates is provided, detailing the interaction between the permanent magnet rotor and the electromagnet stator. The analogy of a donkey chasing a carrot is used to illustrate the continuous rotation of the BLDC motor. The drawback of reduced power output due to only one coil being energized at a time is mentioned, along with a solution to increase torque and power output by energizing a second coil with the same polarity current. The paragraph concludes with a mention of an electronic controller and a Hall effect sensor used to determine the rotor's position and energize the correct stator coils, and a brief note on the outrunner type of BLDC design.

Mindmap

Keywords

💡Brushless DC Motor (BLDC)

A Brushless DC Motor is an electric motor that operates on the principle of electromagnetic induction without the need for brushes to make contact with the rotor. This design contributes to higher reliability, efficiency, and lower noise levels compared to brushed motors. In the video, BLDC motors are highlighted for their lighter weight and longer lifespan, making them ideal for applications requiring high reliability.

💡Permanent Magnet

A permanent magnet is a type of magnet made from materials that maintain their magnetism over time. In BLDC motors, the rotor is a permanent magnet, which interacts with the electromagnets in the stator to produce motion. The permanent magnet's role is crucial as it provides the magnetic field necessary for the motor's operation.

💡Stator

The stator is the stationary part of an electric motor that contains the coil arrangement. In the context of the video, the stator's coils are energized to create electromagnets, which interact with the permanent magnet rotor to produce rotational force. The stator's design and coil arrangement are key to the BLDC motor's functionality.

💡Electromagnet

An electromagnet is a type of magnet in which the magnetic field is produced by an electric current. In the BLDC motor, when DC power is applied to the stator's coils, they become electromagnets, attracting the opposite poles of the permanent magnet rotor. This interaction is fundamental to the motor's operation and rotation.

💡Torque

Torque is the force that can cause rotation about an axis. In the video, it is mentioned that by energizing two coils with the same polarity current, the combined effect produces more torque, which is essential for the motor's power output and its ability to maintain a constant torque nature.

💡Electronic Controller

An electronic controller is a device that manages the operation of the BLDC motor by determining which stator coils to energize based on the rotor's position. This component is vital for achieving continuous and controlled rotation of the rotor, ensuring the motor operates efficiently and effectively.

💡Hall Effect Sensor

A Hall effect sensor is a type of sensor that is often used in BLDC motors to detect the position of the rotor. The information provided by this sensor allows the electronic controller to make informed decisions about which coils to energize, enabling precise control over the motor's operation.

💡Outrunner Type

The outrunner type is a specific design of BLDC motor where the stator windings are on the outside and the rotor is on the inside. This design is contrasted with the inrunner type in the video, where the rotor is on the outside and the stator is on the inside. The outrunner design is discussed in the context of its operational principles.

💡Inrunner BLDC Design

The inrunner BLDC design is an alternative configuration to the outrunner type, where the rotor is on the outside and the stator windings are on the inside. This design is briefly mentioned in the video as an option available in the market, suggesting there are different types of BLDC motors to suit various applications.

💡Power Output

Power output refers to the amount of power a motor can produce. In the context of the video, the power output of a BLDC motor is discussed in relation to the energizing of coils. The video explains how the strategic energizing of coils can increase the motor's power output, which is a significant advantage of BLDC motors.

💡Continuous Rotation

Continuous rotation is the ability of a motor to rotate without interruption. The video emphasizes the importance of an electronic controller and sensor system in achieving continuous rotation in a BLDC motor. This feature is critical for operations that require the motor to run for extended periods without stopping.

Highlights

Brushless DC (BLDC) motors are becoming more popular for their reliability, efficiency, and lower noise compared to brushed DC motors.

BLDC motors are lighter than brushed motors with the same power output.

Brushed DC motors have brushes that wear out and can cause sparking, making them unsuitable for applications requiring long life and reliability.

The rotor in a BLDC motor is a permanent magnet, while the stator has a specific coil arrangement.

Applying DC power to the stator coil energizes it and turns it into an electromagnet, interacting with the permanent magnet rotor.

BLDC motor operation is based on the force interaction between the permanent magnet and the electromagnet, causing the rotor to rotate.

A humorous analogy to remember BLDC operation is the story of a donkey chasing a carrot that keeps moving out of reach.

At any given moment, only one stator coil is energized in a BLDC motor, reducing power output.

To overcome this, the coil behind the rotor can be energized to push the rotor, producing more torque and power output.

This configuration results in a BLDC motor with a constant torque nature.

A small modification to the stator coil can simplify the process of energizing two coils separately.

Connecting one free end of the coils together allows for the power to be applied between coils A and B.

An electronic controller and sensor are used in a BLDC motor to determine rotor position and decide which coils to energize.

A Hall effect sensor is commonly used for determining rotor position in BLDC motors.

The BLDC motor design discussed is known as the outrunner type, while the inrunner design is also available.

The BLDC motor provides a nice introduction to the working principles of brushless DC motors.