How does a DC motor turn up

The working principle of a DC motor.

The rotor of the DC motor interacts with the current and the stator magnetic field to complete the conversion of electrical energy into mechanical energy.

Armature part: The function is to generate electromagnetic torque and induce electromotive force, and carry out energy transformation. Armature windings have many coils or glass wires wrapped in flat steel copper wires or strength enameled wires.

The commutator, also known as the commutator, in the DC motor, its function is to convert the current of the DC power supply on the brush into the communication current in the armature winding, so that the tendency of the electromagnetic torque is stable and unchanged.

The commutator consists of a cylinder composed of many pieces insulated with mica, and the armature windings are connected to two commutator pieces at both ends of each coil. The function of the commutator in the DC generator is to convert the alternating electric heat in the armature winding into the DC electromotive force between the brushes, and the current passes through the load, and the DC generator outputs electric power to the load.

At the same time, there must be an electric current passing through the armature coil as well. It interacts with the magnetic field to generate electromagnetic torque, which tends to be the opposite of the generator, and the original idea is to suppress this magnetic field torque only to change the armature. Therefore, the generator outputs electrical power to the load, and outputs the mechanical power from the original idea, which completes the role of the DC generator in converting mechanical energy into electrical energy.

The role of the rotor is to convert the work generated by the electromagnetic effect into rotational torque output.

The composition of the motor: it is composed of a stator and a rotor.

The stator includes: main magnetic pole, machine base, commutation pole, brush device, etc.

The rotor includes: armature core, armature winding, commutator, shaft and fan, etc.

The principle of DC motor rotation: when the armature is rotated 180°, the conductor CD goes to the N pole, and the conductor AB goes to the S pole, because the current direction supplied by the DC power supply remains unchanged, it still flows from the brush A, and flows out from the brush B after the conductor CD and AB. At this time, the direction of force on the conductor cd changes from right to left, the direction of force on the conductor ab is from left to right, and the direction of the electromagnetic torque generated is still counterclockwise.

Therefore, once the armature is turned, due to the commutator with the commutation effect of the brush on the current, the DC current flows alternately from the conductors AB and CD, so that as long as the coil edge is under the n pole, the direction of the passing current is always the direction of the flow of brush A, and the direction of flow from the brush B when it is below the S pole. This ensures that the current in the coil side at each pole is always in one direction, resulting in a torque that does not change in the direction and enables the motor to rotate continuously.

The principle of a DC motor: an energized conductor is subjected to force in a magnetic field. It can be divided into permanent magnet type or DC electromagnetic type.

The working principle of a three-phase asynchronous motor: three-phase alternating current generates a rotating magnetic field. Three-phase AC motors are divided into stator windings and rotors.

When a symmetrical three alternating currents are introduced into the three-phase stator winding, a rotating magnetic field is generated that rotates clockwise along the inner circular space of the stator and rotor at a synchronous speed n1. Since the rotating magnetic field rotates at n1 rotational speed, the rotor conductor is stationary at the beginning, so the rotor conductor will cut the stator rotating magnetic field and generate an induced electromotive force (the direction of the induced electromotive force is determined by the right-hand rule). Since the two ends of the rotor conductor are shorted by short-circuit rings, under the action of induced electromotive force, the induced current in the rotor conductor will be basically consistent with the direction of the induced electromotive force.

The current-carrying conductor of the rotor is subjected to an electromagnetic force in the stator magnetic field (the direction of the force is determined by the left-hand rule). The electromagnetic force generates electromagnetic torque on the rotor shaft and drives the rotor to rotate in the direction of the rotating magnetic field.

There are two ways to change the direction of rotation of a DC motor:

The first is the armature reverse connection method, that is, the polarity of the terminal voltage of the excitation winding is kept unchanged, and the motor is reversed by changing the polarity of the terminal voltage of the armature winding;

The second is the reverse connection method of the excitation winding, that is, the polarity of the terminal voltage of the armature winding is kept unchanged, and the motor is adjusted by changing the polarity of the terminal voltage of the excitation winding. When the voltage polarity of both changes at the same time, the direction of rotation of the motor does not change.

Separately excited and parallel excitation DC motors generally use the armature reverse connection method to achieve forward and reverse rotation. The reason why the excitation winding reversal method is not suitable for the excitation winding reverse connection method is that the excitation winding turns are more and the inductance is larger. When the excitation winding is reversed, a large induced electromotive force will be generated in the excitation winding, which will damage the insulation of the gate blade and the excitation winding.

The reason why the series excited DC motor should use the excitation winding reverse connection method to achieve forward and reverse rotation is because the voltage at both ends of the armature of the series excited DC motor is high, and the voltage at both ends of the excitation winding is very low, and it is easy to reverse the connection, and the motor locomotive often adopts this method.

When the DC power supply is supplied to the armature winding through the brush, the conductor under the n pole on the surface of the armature can flow through the current in the same direction, and the conductor will be subjected to the torque in the counterclockwise direction according to the left-hand rule; The conductor under the S pole on the surface of the armature also flows through the current in the same direction, and the conductor will also be subjected to a moment in the counterclockwise direction according to the left-handed rule. In this way, the entire armature winding, i.e. the rotor, will rotate counterclockwise, and the input DC energy will be converted into the mechanical energy output on the rotor shaft. Consists of a stator and a rotor, stator:

Base, main magnetic pole, commutation pole, brush device, etc.; Rotor (armature): armature core, armature winding, commutator, shaft and fan, etc.

The rotor of the three-phase asynchronous motor is dragged by the rotating magnetic field generated by the three-phase winding of the stator, and the rotor rotates in which direction the rotating magnetic field formed by the three-phase winding rotates. Therefore, as long as any two wires of the three-phase power line are replaced, the rotating magnetic field of the motor stator is changed, and the rotation direction of the motor rotor is also changed.

Change the polarity of the armature voltageor change the polarity of the excitation.