Brushless dc motors

The brushless dc motor is a type of electric motor, which looks quite similar to the DC motor and is AC synchronous. It is also called as BLDC in short form. Now the question arises what is the difference between the DC motor and the brushless DC motor. As per many experts, the difference lies in the presence of an electronically controlled commutation system. However, this view is regarded as misleading by many persons and they think that the two types of motors are quite different from each other, physically.

In the DC motor, there are brushes that make mechanical contact with the set of different types of electrical contacts on the commutator or the rotor. This forms an electric circuit between the armature coil windings and the DC electrical source. It is to be noted here that when the armature rotates on the axis, the brushes, which are stationary, comes in contact of rotating rotor. In the BLDC or the brushless DC motor, the different types of electromagnet do not move. It is the permanent magnets that move and rotate whereas the armature remains in the static mode. Now the question that arises is how the current is transferred to the moving armature. To get this done, the brush system or the commutator system found in the DC motor is replaced by the intelligent electronic controller. It is to be properly understood here that this controller functions in the same way as far as the power distribution is concerned as is done by the commutator or the brush system in the DC motor. Thus, it is the solid-state circuit that is used in the brushless DC motors to transfer the current.

APPliCATIONS OF BRUSHLESS DC MOTORS

Let us discuss the various applications to which the brushless DC motors are put. It is to be understood here that these types of motors can easily be used in any type of field application processes, where the DC motor is used. So, it can replace the DC motor. The two areas of concern due to which the brushless DC motors are not used to replace the DC motors are the control complexity and the cost. Since there are no brushes to make contact in BLDC, it becomes very difficult to control the various functions. The cost of Brushless DC motors is also more. But it does not mean that these motors are useless. In fact, there are many applications in which this type of motor has domination. There are also some areas of applications where the BLDC motors are used exclusively.

The examples are Computer hard drives, PC cooling fans, CD/DVD players. All these devices are run on brushless DC motors. There are also low speed and low power BLDC that are used in the different types of direct drive turntables. As far as high power and high-speed BLDC motors are concerned, they are used in electric vehicles and various other types of industrial machinery. It is to be noted here that these types of motors are of course AC synchronous and has permanent magnet rotors. For example, one of the most famous cars, the Honda Civic uses BLDC motor in order to supplement the output generated by the internal combustions engine. It is basically done when extra power is needed. The brushless DC motors are also used to start the engine instead of using the conventional solenoid method and the starter.

Lately, the BLDC motors have found a new area of application, due to which its popularity has been increased. This device is the model aircraft. This is an electrically powered model aircraft and has increased the demand for the high performance BLDC Motors. Even there are many people who are now taking out the brushless DC motors out of the hard drives of their computers etc and are using in the different types of radio controlled vehicles. The various parts of BLDC motors are easily available and thus, a person can easily assemble these parts to form a BLDC motor, saving some money in the whole process

So, there are many applications in which the BLDC motors are used exclusively. There are also many applications where these motors perform better than the DC motors. Let us now discuss about the variations that are found in the construction of Brushless DC motors.

CONSTRUCTION OF BRUSHLESS DC MOTORS

As far as the construction of brushless DC motors is concerned, it can easily be constructed in the several physical configurations, which are different from each other. In the most common type of configuration, which is also known as the inrunner configuration, various types of permanent magnets are mounted on the rotor or the spinning armature. The rotor is also surrounded by three stator windings. In other type of configuration, which is called as the outrunner configuration, the radial relationship that exists between the magnets and the coils get reversed. In such configuration, the center is formed by the stator coils and the permanent magnet spins on the rotor, which surrounds the core and is in the overhanging position. This type of motor can be easily used in the applications where there is less space available. It is usually flat and uses rotor plates and the stator, which are mounted face to face. It is to be noted here that there are more number of poles in the outrunner type of motor. These poles are in triplets, which maintain the three groups of the windings. The torque provided is also higher, even at low RPM's. The reader should also understand that in all the types of BLDC motors, the stator coils are stationary.

THUS, BRUSHLESS DC MOTORS ARE QUITE USEFUL

Brushless DC motors are similar to DC motors except for few changes. Though these are costly and the control of these motors is also not easy, there are many applications in which these motors gain advantage. There are also some other applications where the brushless DC motors are used exclusively. Their applications have led many people to take out these motors from PC etc and use them in different types of radio devices. So, it can be rightly said that the brushless DC motors are quite useful.

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