2. DC MOTORS
It converts electrical energy into mechanical energy. Its action is
based on the principle that when a current carrying conductor is
placed in a magnetic field, it experiences a mechanical force ,
whose direction is given by Fleming's left hand rule which in turn
produces torque for rotation.
4. STATOR
A stator is the static part of the DC machine that houses the field windings and receives the supply. A
rotor is the rotating part of the DC machine that brings about the mechanical rotations.
YOKE
The magnetic frame or the yoke of DC motor made up of cast iron or steel and forms an integral part of
the stator or the static part of the motor.
POLES
The magnetic poles of DC motor are structures fitted onto the inner wall of the yoke with screws.
FIELD WINDING
The field winding of DC motor are made with field coils (copper wire) wound over the slots of the pole
shoes in such a manner that when field current flows through it, then adjacent poles have opposite
polarity are produced. The field winding basically form an electromagnet, that produces field flux within
which the rotor armature of the DC motor rotates, and results in the effective flux cutting.
ARMATURE WINDING
The armature winding of DC motor is attached to the rotor, or the rotating part of the machine, and as a
result is subjected to altering magnetic field in the path of its rotation which directly results in magnetic
losses. The armature core are provided with slots made of the same material as the core to which the
armature winding made with several turns of copper wire distributed uniformly over the entire periphery
of the core.
5. COMMUTATOR
The armature core are provided with slots made of the same material as the core to which the
armature winding made with several turns of copper wire distributed uniformly over the entire
periphery of the core. It helps to develop a continuous and unidirectional torque.
BRUSHES
The brushes of DC motor are made with carbon or graphite structures, making sliding contact over
the rotating commutator. The brushes are used to relay the current from external circuit to the
rotating commutator form where it flows into the armature winding. So, the commutator and brush
unit of the DC motor is concerned with transmitting the power from the static electrical circuit to the
mechanically rotating region or the rotor.
6. WORKING
• When armature windings are connected to a DC supply, an
electric current sets up in the winding. Magnetic field may be
provided by field winding (electromagnetism) or by
using permanent magnets. In this case, current carrying
armature conductors experience a force due to the magnetic
field, according to the principle stated above.
• Commutator is made segmented to achieve unidirectional
torque. Otherwise, the direction of force would have reversed
every time when the direction of movement of conductor is
reversed in the magnetic field.
7. DISADVANTAGES OF BRUSHES
• Brush DC motors are inexpensive and reliable and have a high ratio
of torque to inertia. Because they need few or no external
components, they are also suitable for operation under rugged
conditions.
On the downside, the brushes wear down over time and produce
dust; brush motors require periodic maintenance for brush cleaning
or replacement. Other disadvantages include poor heat dissipation
due to limitations of the rotor, high rotor inertia, low maximum
speed, and electromagnetic interference (EMI) generated by brush
arcing.
8. BRUSHLESS DC MOTORS
• Brushless dc motors (BLDC) motors don’t use carbon brushes
or a mechanical commutator. Forcing the rotor to rotate is done
by successively energizing coils around the stator, and
commutation is performed via a complex electronic controller
used in conjunction with a rotor position sensor
• In contrast to the brush DC motor, the permanent magnet is
mounted on the rotor; the stator is made of slotted, laminated
steel and contains the coil windings.
9. CONSTRUCTION
• In this motor, the permanent magnets attach to the rotor. The current-
carrying conductors or armature windings are located on the stator. They
use electrical commutation to convert electrical energy into mechanical
energy.
• The main design difference between a brushed and brushless motors is the
replacement of mechanical commutator with an electric switch circuit. A
BLDC Motor is a type of synchronous motor in the sense that the magnetic
field generated by the stator and the rotor revolve at the same frequency.
10. WORKING
• BLDC motor works on the principle similar to that of a Brushed DC motor. The Lorentz force law
which states that whenever a current carrying conductor placed in a magnetic field it experiences a
force. As a consequence of reaction force, the magnet will experience an equal and opposite force.
In the BLDC motor, the current carrying conductor is stationary and the permanent magnet is
moving. When the stator coils get a supply from source, it becomes electromagnet and starts
producing the uniform field in the air gap. Though the source of supply is DC, switching makes to
generate an AC voltage waveform with trapezoidal shape. Due to the force of interaction between
electromagnet stator and permanent magnet rotor, the rotor continues to rotate.
• With the switching of windings as High and Low signals, corresponding winding energized as
North and South poles. The permanent magnet rotor with North and South poles align with stator
poles which causes the motor to rotate.
11. BLDC MOTOR CONTROLLER
• BLDC motor controllers differ according to the method they use to detect the
rotor’s position. we can make the measurements with the help of position
sensors or using a sensorless technique.
• Hall-effect sensors
• rotary encoders
• variable reluctance sensors
• Resolvers
• optical sensors
12.
13. ADVANTAGES
• Brushless motors are more efficient as its velocity is determined by the
frequency at which current is supplied, not the voltage.
• As brushes are absent, the mechanical energy loss due to friction is less
which enhanced efficiency.
• BLDC motor can operate at high-speed under any condition.
• There is no sparking and much less noise during operation.
• More electromagnets could be used on the stator for more precise control.
14. ADVANTAGES
• BLDC motors do not have brushes which make it more reliable, high life
expectancies, and maintenance free operation.
• There is no ionizing sparks from the commutator, and electromagnetic
interference is also get reduced.
• Such motors cooled by conduction and no air flow are required for inside
cooling.
• BLDC motors accelerate and decelerate easily as they are having low rotor
inertia.
15. DISADVANTAGES
• BLDC motor cost more than a brushed DC motor.
• The limited high power could be supplied to BLDC motor, otherwise,
too much heat weakens the magnets and the insulation of winding
may get damaged.
16. DIFFERENCE BETWEEN BRUSHED DC MOTOR AND
BRUSHLESS DC MOTOR
BRUSHED DC MOTOR
• It uses brushes to deliver current to
the motor windings through
mechanical commutation.
• Lower speed compared to BLDC.
• Control is simple
• Arcs in the brushes generate noise
BRUSHLESS DC MOTOR
• It uses Electrical commutation to
deliver the current.
• Highspeed because of the absence
of brushes and commutator
• Control is complex and expensive.
• Low electrical noise
17. DIFFERENCE BETWEEN BRUSHED DC MOTOR
AND BRUSHLESS DC MOTOR
BRUSHED DC MOTOR
• Periodic maintenance required.
• Moderate efficiency
• Short life
• No controller is required
• Armature winding is on rotor; Fixed
magnets are placed on either side of the
rotating electromagnet
BRUSHLESS DC MOTOR
• Less required in absence of brushes
• High efficiency
• Long life
• Controller is always required to keep
motor running
• Armature winding is on stator and fixed
magnets are on rotor
18. APPLICATIONS
• Brushless DC motors (BLDC) use for a wide variety of application
requirements such as varying loads, constant loads and positioning
applications in the fields of industrial control, automotive, aviation,
automation systems, health care equipments etc.
• Electric vehicles, hybrid vehicles, and electric bicycles
• Industrial robots, CNC machine tools, and simple belt driven systems
• Washing machines, compressors and dryers
• Fans, pumps and blowers.
