The motor is indisputably one of the primary machines in electromechanical engineering. It is a machine that converts electrical energy into mechanical energy. When you see a moving system that uses electricity, the power to move is provided by a motor. Depending on the type of electrical power, there are AC motors and DC motors. Dc motors are further categorized into brush, brushless, and stepper DC motors. This article will focus on brushless motors.
The keyword in this motor is brushless, one can infer that there could be a brushed DC motor. That is true, the brushless motor was developed after the brushed motor had been invented and in use. It is also referred to as an electronically commutated or synchronous dc motor. As the name suggests this motor uses solid-state electronics to control the operation. The electronic controller replaces the traditional brushes and commutators that are present in brushed DC motors.
Construction
The two main parts of a motor are the stator and rotor. This motor has an additional component that makes it unique from other types, that is the electronic controller. The rotor is a permanent magnet that can have a minimum of two poles. The stator is a conductor winding on an iron core that forms an electromagnet. The stator winding is usually three apart from a few that may use one or two winding. An electronic controller is a solid-state that uses transistors (electronic switch) to time power distribution to the stator winding. Hall effect sensors are used to detect stator magnet poles and send a signal to the controller. A pulse with a modulation signal switches the stator.
Operation
Motors operate by electromagnetic principle. The relationship is that varying current creates a magnet with a north and south pole. When the magnetic field from the magnet interacts with the one in the rotor’s permanent magnet there is attraction if unlike poles and repulsion if like poles. The effect is the movement of the rotor since it is free to move. Unlike poles will attract or chase one another and once they meet, movement stops. To avoid this scenario a chasing cycle is sustained by changing the polarity of the electromagnet once the unlike poles meet. The changing of the stator’s electromagnet polarity is achieved by an electronic controller. Commonly, the stator has three winding and by timing, the switching sequence creates an electromagnetic that is always chasing the unlike poles of the rotor. principally, the stator behaves like a three-phase winding and creates electromagnetism to make the rotor rotate in a given direction. To control speed and torque the controller varies switching intervals and stator current respectively. A hall effect sensor is used to provide feedback to the controller on the stator pole position. When a magnetic pole is near the sensor it sends a high signal to the controller. The main difference with brush Dc motors apart from brushes is that while Brush Dc motors have rotors as an electromagnet and thus varied, brushless motors has stator as electromagnets. The rotor, therefore, does not need a power supply which is a big advantage.
Advantages and disadvantages
A Brushless DC motor was invented as a solution to the problem that brushed dc motors had. Some of them are enumerated below;
- High power to weight ratio
- Can operate at high speed
- Easy and instantaneous control of speed and torque.
- High efficiency, no power loss in brushes friction
- Low maintenance requirement, no brushes that wear out
- No sparking is a fire hazard and a source of electromagnetic interference.
- Can hold torque even when stationary i.e., zero RPM
- Can achieve micro-stepping to have slow and fine motion
- Better cooling as heat is lost on stator by conduction, hence rotor can be enclosed.
- Disadvantages
- It cannot operate well in a high heat environment as it destroys the rotor magnetism and wire insulation.
Application
As we have seen above these motors have many advantages thereby giving them a wide array of applications. Some of them include;
- Electronic devices such as computer hard drives.
- Handheld power tools such as drilling machine
- Automobiles motors such as a wiper, windows movers, etc.
- In aircrafts moving parts automation.
- Washing machine motors
- Air conditioners motors
Conclusion
Brushless DC motors are arguably one of the greatest inventions in the electrical world. Its functionality is desirable and this has made them be highly opted for compared to their brushed counterparts. The other advantage is that you can customize electronic control to achieve your desired operation of this motor such as step movement, forward, and reverse among others. What you can do with a brushless motor is limited to your imagination.