Where are DC motors used? Is it better to have a DC motor or an AC motor

The cylindrical grinding of the North II machine, Shanghai Nanyang Motor, is more expensive (relative to the AC one).

DC motors are one of the main types of motors. A DC motor can be used as a generator, can also be used as a motor, used as a DC generator can get DC power supply, and as a DC motor, because of its good speed regulation performance, in many occasions with high speed regulation performance requirements, it is still widely used.

Occasions that require high speed (the speed of AC motor has a bottleneck of 4000rpm, DC can reach more than 14000rpm), occasions with considerable requirements for speed accuracy, occasions without AC power grid, such as some parts of ships, low-voltage occasions (DC motors are generally used below 48V) and so on.

Applications of DC Motors:

Due to the good starting and speed regulation performance of DC motors, they are often used in occasions with high requirements for starting and speed regulation, such as large reversible rolling mills, mine winches, hotel high-speed elevators, gantry planers, electric locomotives, diesel locomotives, city trams, subway trains, electric bicycles, paper and printing machinery, ship machinery, large precision machine tools and large cranes and other production machinery.

Working principle: There is a toroidal permanent magnet fixed in the DC motor, and the current generates ampere force through the coil on the rotor, when the coil on the rotor is parallel to the magnetic field, the direction of the magnetic field will change when it continues to rotate, so at this time, the brush at the end of the rotor is in contact with the conversion piece alternately, so that the current direction on the coil also changes, and the direction of the Lorentz force generated remains unchanged, so the motor can maintain rotation in one direction.

The working principle of the DC generator is to change the alternating electromotive force induced in the armature coil into a DC electromotive force when it is drawn out of the brush end by the commutator and the commutation action of the brush.

The direction of the induced electromotive force is determined according to the right-hand rule (the magnetic inductance line points to the palm of the hand, the thumb points to the direction of the conductor's movement, and the other four fingers point to the direction of the induced electromotive force in the conductor).

The direction of the force on the conductor is determined by the left-handed rule. This pair of electromagnetic forces forms a moment acting on the armature, which is called electromagnetic torque in a rotating electric machine, and the direction of the torque is counterclockwise, in an attempt to make the armature rotate in a counterclockwise direction. If this electromagnetic torque can overcome the resistance torque on the armature, such as friction and other load torques, the armature can rotate in a counterclockwise direction.

Advantages and disadvantages of DC motors vs AC motors.

First, the advantages of DC motors.

1.The DC motor has good starting characteristics and speed regulation characteristics.

2.The torque of the DC motor is relatively large.

3.Repairs are cheaper.

4.The DC of the DC motor is more energy-saving and environmentally friendly than the AC.

Second, the disadvantages of DC motors.

1.DC motor manufacturing is more expensive.

2.There are carbon brushes.

3. Advantages of AC motors.

1.AC motors are cheaper to manufacture.

2.With the development of vector frequency conversion technology, it has been possible to simulate direct current with frequency conversion motors.

3.Compared with DC motors, it has enough advantages in simple structure, easy maintenance, low environmental requirements, energy saving and improving productivity, so that AC speed regulation has been widely used in industrial and agricultural production, transportation, national defense and daily life.

Fourth, the shortcomings of AC motors.

1.The start-up and speed regulation of AC motors are poor.

AC motors can be divided into synchronous motors and asynchronous motors according to the speed.

1. Synchronous motor.

There are three main modes of operation of synchronous motors, which are used as generators, motors, and compensators. As a press release, motor operation is the most important mode of operation of synchronous motors, and operation as a motor is another important mode of operation of synchronous motors. The power factor of the synchronous motor can be adjusted by pressing the spring cavity, and the application of a large synchronous motor can improve the operating efficiency when the speed regulation is not required.

In recent years, small synchronous motors have begun to be used more in frequency conversion speed regulation systems.

The synchronous motor can also be connected to the grid as a synchronous compensation machine. At this time, the motor does not carry any mechanical load, and sends the required inductive or capacitive reactive power to the power grid by adjusting the excitation current in the rotor, so as to achieve the purpose of improving the power factor of the grid or regulating the grid voltage.

2. Asynchronous motor.

An asynchronous motor is a type of AC motor in which the ratio of the rotational speed at load to the frequency of the connected grid is not constant. It also varies with the size of the load. The higher the load torque, the lower the speed of the rotor.

Asynchronous motors include induction motors, doubly-fed asynchronous motors, and AC commutator motors. Induction motors are the most widely used, and can generally be called asynchronous motors without causing misunderstanding or confusion.

Advantages: simple structure, easy to manufacture, cheap and easy to run.

Disadvantages: power factor lag, low power factor at light load, and slightly poor speed regulation performance.

1. The working principle is different:

The alternator is made according to the principle of electromagnetic induction, that is, whether it is the movement of the conductor (coil), the rental of the diesel generator or the movement of the magnetic field, as long as there is a relative movement between the conductor (coil) and the magnetic field, and the conductor (coil) cuts the magnetic field lines, it will generate electromotive force in the conductor (coil), that is, it can be called electricity generation when it moves; The DC motor is made according to the principle that the current-carrying conductor (coil) moves under force in the magnetic field, that is, it can be called electric only when it is energized.

2. The structure is different

The alternator coil is connected to a copper ring (slip ring) at each end, that is, the brush; The DC motor coil is connected to a copper half-ring at both ends called a commutator, which plays a reversing role in the current of each winding, so that the alternating current becomes direct current.

3. The direction judgment is different

The alternator induces the direction of the electromotive force, which is determined by the right-hand rule; The direction of rotation of the DC motor is determined by the left-handed rule.

4. The conversion of energy is different

The alternator inputs mechanical energy and outputs electrical energy; Diesel generator rental is a rotating machine that converts mechanical energy into electrical energy; The DC motor inputs electrical energy and outputs mechanical energy, that is, the transfer motor that converts electrical energy into mechanical energy.

DC motor performance correlation.

1. DC separately excited motor: there is no electric connection between the excitation winding and the armature, and the excitation circuit is supplied by another DC power supply. Therefore, the excitation current is not affected by the armature terminal voltage or the armature current.

2. DC parallel excitation motor: the circuit is parallel, shunt, and the voltage at both ends of the parallel excitation winding is the voltage at both ends of the armature, but the excitation winding is wound with a thin wire, and its turns are many, so it has a large resistance, so that the excitation current through him is smaller.

3. DC series excitation motor: the current is connected in series, the voltage divider, and the excitation winding are connected in series with the armature, so the magnetic field in this motor changes significantly with the change of armature current. In order to prevent large losses and voltage drops in the excitation winding, the smaller the resistance of the excitation winding, the better, so the DC series motor is usually wound with a thicker wire, and his turns are less.

4. DC compound excitation motor: The magnetic flux of the motor is generated by the excitation current in the two windings.

The above content refers to Encyclopedia - DC Motor.

Encyclopedia - Generator.

In general, AC motors are better than DC motors.

Difference Between DC and AC Motor:

1. The external power supply is different.

DC motors use DC as a power source; AC motors use alternating current as a power source.

2. The structure is different.

The principle of the former is relatively simple, but the structure is messy and not easy to protect; The latter principle is messy but the structure is relatively simple, and it is easier to protect than DC motors.

3. The movement in the magnetic field is different.

DC motors have a stationary magnetic field in which the conductor moves; The AC motor rotates in a magnetic field, while the conductor does not move.

4. The speed regulation is different.

The DC motor can complete smooth and economical speed regulation, without the cooperation of other equipment, and only need to change the input or excitation voltage and current to complete the speed regulation; The AC motor itself cannot complete the speed regulation, and the chain Chunchang needs to rely on frequency conversion equipment to complete the speed change.

5. The structure of the motor is different.

DC motors are driven by direct current, so there is no direct generation of rotating magnetic fields. It relies on the commutator that rolls with the rotor to change the direction of the current entering the rotor at any time, so that the polarity of the magnetic field between the rotor and the stator is always opposite, so that the rotor rolls; However, since the AC motor uses an AC power source, only the stator coils are arranged in phase, so a rotating magnetic field is naturally generated. <>

It is a rotating machine that converts mechanical energy into direct current energy.

Saturation coefficient: ku=ac ab When the magnetic current of the excitation base is small, the magnetic circuit of the motor is not saturated due to the small magnetic flux, and the no-load characteristics are in a straight line, and the extended ray is called (air gap line).

The DC motor is divided into two parts: stator and rotor. The stator is composed of the main magnetic pole, the frame, the commutation table, the brush device, etc. The rotor includes: armature core, armature winding, commutator, shaft, and blower lamp.

When you add DC to a DC motor, a current flows through the coil, and according to the law of electromagnetic force, the remaining conductor will be affected by the electromagnetic force, and the direction is determined by the left-hand rule.

DC Generator:

A rotating device that converts direct current energy into mechanical energy. The stator of the motor provides the magnetic field, the source of the DC electric training hall provides the current to the rotor windings, and the commutator aligns the rotor current with the torque generated by the magnetic field. According to whether the ordinary brushless commutator is configured, it can be divided into two types of DC motors, including brushless DC motors and brushless DC motors.

Brushless DC motor (BLDC) is a new type of DC motor developed with the development of microprocessor technology in recent years, the application of new power electronic devices with high switching frequency and low power consumption, the optimization of control methods and the emergence of low-cost, high-magnetic level permanent magnet materials.

Brushless DC motor is to maintain the traditional DC motor speed control performance and no sliding contact and commutation sparks, high reliability, long service life, low noise advantages, so in aerospace, CNC machine tools, robots, electric vehicles, computer peripherals and household appliances, etc., has been widely used.

According to the different power supply methods, brushless DC motors can be divided into two categories: square wave brushless DC electric with front hidden machine, whose back potential waveform and power supply current waveform are rectangular waves, also known as rectangular wave permanent magnet synchronous motors; For a sine wave brushless DC motor, both the back potential waveform and the power supply current waveform are sine waves.

The above content reference:Encyclopedia - DC Motors.

DC rot motors have a wide range of applications in various fields, and here are some of the common uses of DC motors:

Industrial applications: DC motors are widely used in the field of industrial automation to drive various mechanical equipment and tools, such as machine tools, conveyor belts, pumps, fans, etc. Its non-leakage speed regulation, high torque and precise control make it an important drive unit in industrial production.

Transportation: DC motors play an important role in the transportation sector. The drive motor in electric and hybrid vehicles typically uses a DC motor to provide power and drive the vehicle to operate.

Household appliances: DC motors are widely used in household appliances, such as washing machines, vacuum cleaners, blenders, fans, air conditioning units, etc. Its high efficiency, adjustable speed, and low noise characteristics make it ideal for home appliances.

Information technology equipment: DC motors are widely used in information technology equipment such as computer hard drives, printers, scanners, etc. Its fast response, high accuracy, and reliability make it suitable for equipment that requires fine control and high-speed operation.

Medical equipment: DC motors play an important role in medical equipment, such as surgical instruments, medical machinery, electric wheelchairs, etc. Its high efficiency, low noise and adjustable speed are essential for the operation and control of medical equipment.

Agriculture and horticulture: DC motors have a variety of applications in agriculture and horticulture, including irrigation systems, agricultural machinery equipment, greenhouse ventilation systems, and more. Its adjustable speed, high torque, and durability make it suitable for different agricultural tasks and needs.

In short, DC motors play an important role in various fields due to their adjustable speed, high torque, precise control and high efficiency, and meet the power needs and motion control requirements of different applications.

Hollis is mainly engaged in the R&D, production and sales of intelligent equipment manufacturing, providing high-end equipment and intelligent chemical factory solutions for electric drive, electronic control, electrical equipment and precision electronics of new energy vehicles.