A BLDC motor powering a micro remote-controlled airplane. The motor is connected to a microprocessor-controlled BLDC controller. This 5-gram motor produces more thrust than twice the weight of the entire plane. Being an outrunner, the rotor-can containing the magnets spins around the coil windings on the stator.A brushless DC motor (BLDC) is an AC synchronous electric motor that from a modeling perspective looks very similar to a DC motor. Sometimes the difference is explained as an electronically controlled commutation system, instead of a mechanical commutation system, although this is misleading, as physically the two motors are completely different.
The Difference between Brushed and Brushless Motor
Brushed Motor:In a conventional (brushed) DC motor, the brushes make mechanical contact with a set of electrical contacts on the rotor (called the commutator), forming an electrical circuit between the DC electrical source and the armature coil-windings. As the armature rotates on axis, the stationary brushes come into contact with different sections of the rotating commutator. The commutator and brush system form a set of electrical switches, each firing in sequence, such that electrical-power always flows through the armature coil closest to the stationary stator (permanent magnet).
Brush less motor:In a BLDC motor, the electromagnets do not move; instead, the permanent magnets rotate and the armature remains static. This gets around the problem of how to transfer current to a moving armature. In order to do this, the brush-system/commutator assembly is replaced by an intelligent electronic controller. The controller performs the same power distribution found in a brushed DC motor, but using a solid-state circuit rather than a commutator/brush system.
Brushed Vs Brush less - Which one wins?
BLDC motors offer several advantages over brushed DC motors, including and higher efficiency reliability, reduced noise, longer lifetime (no brush erosion), elimination of ionizing sparks from the commutator, and overall reduction of electromagnetic interference (EMI). The maximum power that can be applied to a BLDC motor is exceptionally high, limited almost exclusively by heat, which can damage the magnets.
Disadvantage of Brushless over brushed motors
Brush less DC motor main disadvantage is higher cost which arises because of two reasons:
1.) First, BLDC motors require complex electronic speed controllers to run.
2.) Brushed DC motors can be regulated by a comparatively trivial variable resistor (potentiometer or rheostat), which is inefficient but also satisfactory for cost-sensitive applications.
Efficiency factor -
BLDC motors are considered to be more efficient than brushed DC motors. This means that for the same input power, a BLDC motor will convert more electrical power into mechanical power than a brushed motor, mostly due to the absence of friction of brushes. The enhanced efficiency is greatest in the no-load and low-load region of the motor's performance curve. Under high mechanical loads, BLDC motors and high-quality brushed motors are comparable in efficiency.
Variation in Construction of Brush less DC motors
Brush less DC motors come in two different configuration:
1.) Wye configuration.
2.) Delta configuration.
A motor with winding in delta configuration gives low torque at low rpm but can give higher top rpm.
Although efficiency is greatly affected by the motor's construction, the wye winding is normally more efficient.
Applications
The Honda Civic hybrid car uses a BLDC motor to supplement the output of the internal combustion engine when the extra power is needed. It is also used to start the engine versus a conventional starter and solenoid method.
The Segway Scooter also used BLDC technology.
A number of electric bicycles use BLDC motors that are sometimes built right into the wheel hub itself, with the stator fixed solidly to the axle and the magnets attached to and rotating with the wheel. The bicycle wheel hub is the motor. This type of electric bicycle also has a standard bicycle transmission with pedals, gears and chain that can be pedaled along with, or without, the use of the motor as need arises.
Radio controlled car also uses brushless DC motors for higher efficiency but is expensive than conventional motors.
Posted by: Raja Babu Dwivedy.
ID: 4810750499.
Reference: http://en.wikipedia.org/wiki/Brushless_DC_electric_motor.
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