DC motors belong to a class of rotary motors that convert direct current (DC) energy into mechanical energy. Just like its AC motor cousin, it is an electric motor with alternating current, AC, as its power source. In the commercial market, the most popular type of DC motor relies on the force generated by the magnetic field. Almost all types of DC motors have some internal mechanisms, which is electromechanical or electronic, to periodically change the direction of current in part of the motors as designed to be. DC motors are the first widely used motors because they can be powered by existing DC lighting distribution systems. Therefore, the speed of DC motors can be managed over a wide range by using either a variable supply voltage, or it may be achieved by changing the strength of the current in its field windings.
In our daily life, small DC motors are used for tools, toys, and electrical appliances, which is the daily work of modern lifestyles. The universal motor can operate on direct current, but it is a lightweight brushed motor used in portable power tools and appliances. There are currently larger DC motors that are used in the propulsion of electric vehicles as well as elevators and hoists, and also applied in industrial applications in the drives for steel rolling mills.
However, the innovation of power electronics technology allows many functions of AC motors to be replaced by AC motors in many applications. AC motors are electric power motors driven by AC power, and usually using AC power as the power source. An AC motor consists of two basic parts: an outside stator whose coils are supplied with alternating current to generate a rotating magnetic field and an inside rotor, which is connected to the output shaft and generates a second rotating magnetic field for operation.
In fact, the rotor magnetic field depends on the manufacturer's blueprint and customers' application considerations. This is why AC motors have become very popular motor options in the market today. It is widely used in various industrial and household fields due to its convenient characteristics, but simple DC motors are designed with a stationary set of magnet in the stator part and an armature with one or more insulated wire windings. The winding is wound on a soft iron core, which concentrates the magnetic field, so the winding usually has multiple turns around the core. In large motors, there can even be multiple parallel current paths to achieve better performance. Regarding the ends of the wire windings, they are connected to a commutator, which allows each armature coil to be energized in turn, and also connects the rotating coil to an external power source via a brush. In the next section, we will further discuss advanced brushless DC motors.
BLDC motor is the abbreviation of brushless DC motor, also known as electronically commutated motor, its abbreviated form is ECM or EC motor. It is also known as synchronous DC motor and is a popular term for the public. The synchronization feature is an advantage of this type of motor. The BLDC motor is a synchronous motor driven by direct current electricity through an inverter that emits an alternating current electric current to motivate each phase of the motor through a closed loop controller.
Some people may want to know the function of the controller. In fact, the controller provides current pulses to the motor windings to control the torque and speed of the motor equipment. In general, the structure of a brushless motor system is basically the same as or even similar to a permanent magnet synchronous motor, abbreviated as PMSM, and the former can be recognized as a switched reluctance motor or an induction motor, but not a synchronous motor. Speaking of the advantages of brushless motors compared to brushed motors, the former design has a higher power to weight ratio, higher speed, better electronic control, and lower maintenance costs. As a result, based on these advantages, brushless DC motors are widely used in many scientific applications.
Some machine tools belong to the machining center series are tried to be versatile, and the corresponding servo motors used in details are also expected to be versatile too. Although they are not as flexible as machining centers, they are also very agile in terms of motion control. Therefore, they are often used to customize specific tasks of a project. As a result, the precision issue is even stricter than ever before. Consumers from the market demand for better quality, faster speed, and shorter cycle time. The trends in the manufacturing industry become severe for manufacturers, but BLDC motors are helping them overcome obstacles to success in the commercial market.
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