All That You Need To Know About BLDC Motors

BLDC Motor, or Brushless DC Motor, is a motor that uses DC electric power supply. It differs from the standard electric motors as it doesn’t have brushes and uses an electronic drive to feed the windings of the stator. The motor uses permanent magnets in the rotor because it doesn’t need an induced current, unlike the induction motors. It is a highly efficient motor in energy conservation & produces torque over a vast speed. 

Commonly, these motors are used for machine tools & equipment, robotics, computer parts, and electric power generation. 

In this blog, we’re going to take a deeper look at BLDC motors so that you can have a better understanding while using them for your industrial applications. 

Advantages 

• BLDC motors require less maintenance as there are no brushes to clean, inspect, or replace. 
• Compact compared to Brushed DC motors.
• Reliable, energy efficient & long-lasting. 
• Speed can be adjusted by controlling the input DC Voltage. 
• Have lower inertia, which gives a faster response to reference commands. 
• Generate lower radio frequency interference. 
• Ensure better heat removal with a stator (heat generating component) placed outside of the motor. 
• Can operate silently without producing a lot of acoustic noise.  
• Are cooled by conduction and not dependent on air flow.

Types of BLDC Motors

• Inner Rotor Motor

In this type of motor, the rotor is fixed inside the stator and a permanent magnet is placed outside the rotor. Owing to the small size of rotor & low moment of inertia, this motor performs well in giving good acceleration & deceleration responsiveness. The rotor doesn’t insulate the heat inside, so the heat gets dissipated easily. Hence, this is a compact motor with an excellent output power.  

• Outer Rotor Motor

In this type of motor, the rotor is fixed outside the stator and a permanent magnet is placed inside the rotor. Usually, a cup-shaped rotor is not recommended because there is a prime moment of inertia. Hence, the acceleration & deceleration responsiveness is poor compared to inner rotor motors. The rotor magnets trap the heat inside, and do not allow it to get dissipated outside. 

• Disk Rotor Motor

This type of motor includes a stator with windings & pole sensors mounted on the circuit board. The permanent magnet is fixed on the rotor surface, so it's parallel to the stator. It contains no shaft, hence the load is installed in the rotor. It helps to stabilise the speed with a lighter load. 

Common Applications

BLDC motors are ideal for a range of applications, such as:

• Electric & hybrid vehicles & electric bicycles
• Washing machines, dryers, vacuum cleaners & compressors
• Computer hard drives & DVD players 
• Cordless power tools
• Electric fans, pumps & blowers 
• Robotics, CNC machine tools, & actuators 
• Radio controlled transport model, such as cars, helicopters & planes

How does a BLDC Motor work? 

A BLDC motor works similar to a Brushed DC motor. It is based on the Lorentz force law, which shows that when a combination of current & conductor is placed in a magnetic field; it witnesses a force. Due to this reaction, the magnet sees an equal & opposite force. 

These motors have a conductor carrying current in a non-moving state and a permanent magnet in a moving state. When the stator gets a supply of current from the source, it gets electromagnetic & leads to a uniform field in the air gaps. The supply comes from DC, which makes the switching produce an AC voltage waveform. Owing to the force of interaction between the stator & magnet rotor, the rotor keeps moving. 

When the windings switch between high & low signals, the adjacent winding is energized into north & south poles. Then, the magnet rotor with north & south poles lines up with the stator, which helps the brushless motor to operate efficiently. 

BLDC motor is designed with ferrites as rotor poles to examine how far it can demagnetize if there is an extreme armature reaction. Generally, the ferrite demagnetizes easily at lower temperatures. This is why the interest in ferrite magnet motors is increasing rapidly. 

Summing Up 

BLDC Motors are a right alternative over other electric motors. The development of sensorless technology is giving a great boost to these motors in terms of their size, cost & reliability. Therefore, they are increasingly used in modern devices that require low noise & low heat operations. 

Alisha Coils & Transformers (A Unit of Cosmo Ferrites Limited) is a leader in designing & manufacturing transformer and line filters used in  BLDC motors driver PCB. Their products are produced keeping in mind the international standards of quality & safety. You can reach out to their team for any queries or supply requirements.