Some basic concepts of DC motor

by:V&T Technologies     2020-01-05
DC motor is the most commonly used motor in robot technology. DC motors have various shapes and sizes: permanent magnet iron core, permanent magnet iron-free rotor, permanent magnet brushless, winding series, winding parallel, winding compound, variable reluctance stepper, permanent magnet stepper and Hybrid Stepping Motor. Another way to characterize DC motors is brush type and brushless DC motors. This feature refers to the commutation mode used in the motor, which converts direct current from the battery into alternating current required to generate motor action. If the brush mechanically performs this kind of commutation, the commutation piece at the end of the rotating rotor physically slides fan to the fixed brush connected to the motor terminal. These types of motors are Brush DC motors. For brushless motors, direct current is electronically converted into alternating current in the rotor through position sensors and Microprocessor controllers, so brushes are not required. Brush Motors are cheaper than brushless motors and are more commonly used. Compared with the carbon brush type, the advantages of brushless motors are that they have reduced friction, so their service life is longer, and the motors can be better controlled. In addition, brushless motors generate less radio frequency interference. However, brushless motors also have some disadvantages, such as the need for a wider range of control circuits to commute electronically. Traditional DC motors are composed of coils and magnets, which generate motion through electricity. Stator of DC motor assembly: the stator consists of permanent magnet or electromagnetic winding and generates a fixed magnetic field around the rotor, which occupies the central part of the motor. Rotor (Armature) The rotor consists of one or more electrical windings surrounding the armature arm. These windings generate magnetic fields when excited by external current. The magnetic pole generated by the magnetic field of the rotor is attracted by the opposite magnetic pole generated by the stator magnetic field and repelled by the similar magnetic pole, which causes the rotor to rotate. The commutator DC motor does not use an external current switching device, but uses a mechanical connector called a commutator, which is a segmented sleeve usually made of copper and mounted on a rotating shaft. Current /-Provide the commutator with the help of the brush. Brush: with the rotation of the motor, the brush slides on the commutator, thus generating variable magnetic fields in different arms through the commutator connected to the winding. Therefore, when a voltage is applied to the brush, a dynamic magnetic field is generated in the motor. How does the DC motor work? When current passes through wires or wire coils, a magnetic field is generated. The magnetic field is opposite to the permanent magnet arranged on the right side of the coil. Therefore, the upward or downward force depends on the right hand rule. When the motor rotates, the current direction will change to another direction. Therefore, the polarity of the electromagnetic force is always opposite to that of the permanent magnet. Therefore, as long as the power is continuously provided, the motor will remain rotating. Important characteristics of DC motor. When you want to use DC motor in robot or Mechatronics project, you should consider some basic attributes, such as direction, speed, voltage, current, power and torque. Direction: DC motor mainly has two terminals to apply voltage. When a voltage is applied between these terminals, the motor starts to rotate in one direction, and when the polarity of the applied voltage is reversed, the rotation direction will also be reversed. Therefore, the polarity of the applied voltage determines the direction of the motor, while the voltage amplitude determines the speed of the motor. Speed: The speed of the motor, at the number of revolutions per minute (rpm) Is the unit, depending on the applied voltage and load. Voltage: each DC motor has a specified voltage that indicates the nominal voltage or applied voltage that causes the motor to operate under its normal conditions. In fact, this nominal voltage is important in the project because it represents the maximum recommended voltage. Current: when the motor is powered by a nominal voltage, the current depends on the load and increases with the load. Therefore, it is important not to let the motor run under excessive load and stop the motor. Power: The power of a motor is the product of its voltage and current. Torque: torque defines the product of the force multiplied by the distance from the center of the motor shaft. Gear DC motor DC motor usually operates at too high speed and too low torque. In order to use these motors in robot applications, these characteristics should be improved. The gearbox is used for this purpose. Connecting the shaft of the motor to the gear train will cause the output shaft of the gear train to rotate much slower and transmit much larger torque than the input shaft. DC motors with gear boxes on the shaft are called reducer DC motors, which are most suitable for building many amateur robots. Tag dc motor
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