BLDC motor for defence, medical and industrial industries

1. Brushless DC Motors
Confused about motors? Understand the principle and applications of these high efficiency
motors.
What is a Brushless DC Motor?
A Brushless DC Motor (BLDC) is a brushless motor which is powered by a direct current voltage
supply. In conventional DC motors, brushes are used to transfer the power to the rotor as they
turn in a fixed magnetic field, while the brushless DC motors are commutated electronically,
thereby eliminating the use of brushes.
BLDC motors are broadly used in various applications owing to their high efficiency and
exceptional controllability. It also has power-saving advantages as compared to other types of
motor.
Construction of BLDC Motors
In a BLDC motor, the mechanical commutator used in the conventional DC motor is replaced
with an electric switch circuit. A brushless DC Motor is basically a type of synchronous motor.
Therefore, the magnetic field generated by the stator and the rotor revolve at the same
frequency.
A BLDC motor consists of the following parts :
1. Stator
The stator of a BLDC motor is similar to the one used in an induction motor. The stator is
built of steel laminations that are stacked together with slots for winding which are axially

2. cut.. Most BLDC motors consist of three stator windings that are connected in a star or
‘Y’ arrangement.
2. Rotor
The rotor of a BLDC motor consists of permanent magnets (Samarium Cobalt (SmCo),
Neodymium (Nd), alloy of Neodymium, Ferrite and Boron (NdFeB)). The arrangement of
poles can vary according to the number of poles depending on the application of the
motor.
3. Position Sensors (Hall Sensors)
Since BLDC motors are commutated electronically, the windings of the stator must be
energized in a sequence and the position of the rotor must be known to precisely
energize a particular set of stator windings, in order to rotate the motor.
A Position Sensor or a Hall Sensor is a sensor that works on the principle of Hall Effect.
Its function is to detect the position of the rotor and transform it into an electrical signal.
These sensors are embedded into the stator to detect the rotor’s position. Usually, three
Hall sensors are required in a BLDC motor.
Advantages of BLDC Motors
Following are some of the advantages of BLDC motors :
● High efficiency
● Reduced motor size
● Superior thermal characteristics
● Light weight
● Longer lifetime
● No maintenance due to lack of brushes
● No sparking
● Steady operation
● Variable speed
● Excellent controllability
● High output power to size ratio
● Higher speed range
● Lower electric noise generation

3. BLDC motors can be controlled using feedback mechanisms to give specifically the required
torque and rotation speed. Precision control, in turn, lessens energy utilization and heat
generation. In certain cases, where motors are powered by battery, the precision control
enhances the battery life.
BLDC motors also offer high durability and low electric noise generation owing to the lack of
brushes. With brushed motors, the brushes and commutator wear down because of the
continuous moving contact, and also produce sparks at the point of contact. Particularly,
electrical noise is a consequence of the strong sparks that happen to take place in the areas
where the brushes pass over the spaces in the commutator. Therefore, BLDC motors are often
considered preferable in applications where it is important to avoid electrical noise.
Disadvantages of BLDC Motors
Following are some of the disadvantages of BLDC motors :
● Cost
● Limited Constant power range
● Safety
● Demagnetization
● High-Speed Performance
The cost of a BLDC motor is relatively higher when compared to a conventional brushed DC
motor. The electronic controller also elevates the overall cost of the complete setup, as in a
traditional motor. A less expensive mechanical commutation setup involving brushes is used.
When a BLDC motor is operated at low speed, slight vibrations take place during low-speed
rotation. However, the vibrations are reduced at high speed. Due to the inherent natural
vibration frequency of the BLDC motor, sometimes this natural frequency is capable of matching
or coming closer to the vibration frequency of the body or plastic parts resulting in the
occurrence of a phenomenon, known as resonance. However, this resonance can be minimized
by adjustment. The resonance phenomenon is commonly observed in various BLDC motor
based devices. The brushed DC motors are easy to operate as they have simple wiring. The
positive terminal is connected to the positive wire and the negative terminal is connected to the
negative wire and the motor starts rotating. However, in the case of a BLDC motor, wiring and
operation of the motor are not that smooth and effortless. This is because of the involvement of
electronic control and its connection to all the electromagnets.
A large constant power range is important for achieving a high vehicle efficiency. It is impossible
for a BLDC motor to achieve a maximum speed greater than twice the base speed. During the
manufacturing process of the BLDC motor, it might result in being dangerous because the large
rare earth permanent magnets can attract scattered metal objects. In case of a vehicle crash, if

4. the wheels spin freely and the motor is still excited by permanent magnets, high voltages will
appear at the motor terminals. This can endanger the passengers or rescuers. The permanent
magnet can be demagnetized by applying a huge reverse magnetomotive force and increasing
the temperature. The critical demagnetization force is distinct for each permanent magnet
material. Surface mounted motors of permanent magnets fail to achieve high speeds. This is
because of the limitation by the mechanical strength of the assembly between the rotor yoke
and the permanent magnets.
Applications of BLDC Motors
Considering the long list of advantages, BLDC motors can be used in numerous applications,
ranging from automotive to industrial applications. They can be used in medical equipment,
home appliances, building controls and industrial automation. They can also be used to drive
vacuum machines. These brushless motors can also be used to spin hard disc drives. Here,
their durability keeps the drives operating dependably over the long term. The power efficiency
of these motors contributes to energy reduction in an area where this is becoming increasingly
important. Some applications that use the BLDC motors are :
● Consumer electronics
● Transport
● Heating and ventilation
● Industrial engineering
● Model engineering