Introduction, working principle and classification of motor

Ⅰ. Introduction of the motor

Motor, also known as electric machinery, is a general term for a conversion device between mechanical energy and electrical energy. It refers to a machine that operates by electromagnetic induction and has relative moving parts. It can convert electrical energy into mechanical energy or convert mechanical energy into electrical energy. The discipline that studies electrical machines is called electromechanics.

The motor generates a magnetic field in the conductor through the current, and then uses the interaction between the magnetic field and the current to make the electromotive force generate rotational motion.

The basic structure of an electric motor includes a stator and a rotor. The stator is a stationary part, usually consisting of windings and a core. The rotor is the rotating part, usually composed of windings and iron core.

The motor converts electrical energy and mechanical energy in two directions, and most of them use the principle of electromagnetic induction. A motor that converts mechanical energy into electrical energy is usually called a "generator"; a motor that converts electrical energy into mechanical energy is called a "motor". In addition, there are other new motors, such as ultrasonic motors (using piezoelectric effect), which do not use the principle of electromagnetic induction. However, a stationary motor refers to a transformer, which converts electrical energy at one voltage to electrical energy at another voltage.

Ⅱ. Working principle of motor

The working principle of the motor is based on two important physical phenomena of electromagnetic induction and Lorentz force. The specific working principle varies according to different types of motors, and the working principles of the main motor types:

1. AC motor (AC motor) working principle:

AC motors are mainly divided into two types: synchronous motors and asynchronous motors.

Synchronous motor: Its rotor runs synchronously with the rotating magnetic field, that is, the speed of the rotor exactly matches the frequency of the power supply. When the external AC power is applied to the stator, a rotating magnetic field is formed, and the rotor of the synchronous motor is subjected to the action of the magnetic field and rotates synchronously with it.

Asynchronous motor: also known as induction motor. Its stator is wound with a coil, and when an external AC power is applied to the stator, a rotating magnetic field is formed. There are no coils inside the rotor, so it is not directly connected to the power supply. However, due to the existence of the rotating magnetic field, the conductor in the rotor generates an induced current, which in turn generates a Lorentz force, causing the rotor to start rotating.

2. Working principle of stepper motor:

A stepper motor is a special motor that converts electrical pulse signals into precise angular displacement or rotational motion. The working principle of a stepper motor is based on the interaction of electromagnetic induction and electromagnetic force.

The basic structure of a stepper motor consists of a number of electromagnetic windings (often called phases), each with a magnetic pole on it. The rotor is usually made of magnetic material with permanent or magnetized poles.

A stepper motor is an electric motor that converts electrical impulses into rotational motion. It consists of multiple electromagnetic windings, each called a phase. When electrical pulses are applied to the windings sequentially in a specific sequence, the resulting magnetic field causes the rotor to respond to the magnetic field between the cogs in sequence, causing the rotor to rotate step by step.

Stepper motors are divided into two types: single-phase stepper motors and dual-phase stepper motors:

Single-phase stepper motor:

A single-phase stepper motor has two phases (phase A and phase B). When energized, the corresponding winding generates a magnetic field. When current flows through the phase A winding, a magnetic pole is formed, and when the current stops passing through this winding, the magnetic pole disappears. Likewise, the B-phase winding also generates magnetic poles. Controlling the on and off of the current can control the movement of the stepper motor.

Two-phase stepper motor:

A bi-phase stepper motor has two phases (phase A and phase B) and each phase has two windings called A1, A2 and B1, B2. In a two-phase stepper motor, adjacent windings usually exhibit reverse polarity, that is, the polarity between A1 and A2, B1 and B2 is reversed.

3. Working principle of DC motor

In a compound DC motor, the magnetic field interaction between the armature winding and the permanent magnets causes the rotation of the rotor. At the same time, the rotation of the rotor remains stable due to the constantly changing direction of the current on the armature winding (connected to the armature winding through the brushes and connected to the external power supply through the brushes).

In a permanent magnet DC motor, the magnetic field of the permanent magnets is constant. When current passes through the armature winding, the magnetic field generated by the current interacts with the magnetic field of the permanent magnet to form a torque. This torque causes the rotor to start spinning.

Ⅲ. Principle of Motor Rotation

First, you only need a battery, some wires, and a light bulb to form a circuit. The current flowing in the circuit will make the light bulb glow. If you cut the wire, the current will stop flowing. Therefore, we need to add a switch to control the free on-off of the circuit. If you take the battery out and turn it over, the current will flow in the opposite direction and the bulb will glow.

Some devices work or not depending on the direction of this current. After having these foundations, let’s see the magnetic block next. It has a north pole and a south pole, which can attract metal objects. If you take another magnetic block, their different poles will attract each other, and the same poles will repel each other.

The shape of this magnet does not have to be a rectangle, it can also be a square, but the magnetism of the magnet will not disappear, so it is also called a permanent magnet. Its interior is composed of magnetic chips arranged in a uniform direction, which is why the magnetic field is formed. Drill a small hole in the middle of the permanent magnet, insert a central axis so that it can rotate freely, then another magnet is close to it, it will rotate immediately until the magnets with opposite polarities are adjacent to each other, change the direction of the next magnet, the same sex The result of reprimand will cause another spin. If the polarity of the magnet next to it is continuously switched, the magnet with the rotating shaft will continue to rotate.

If it is replaced by a metal bolt, its internal magnetic heads are messy, so there is no magnetism. If you wrap a coil of wire on it, and then connect the circuit, the current on the coil will force the above magnetic chips to be arranged in the same direction, which is equivalent to a magnet with north and south poles, or an electromagnet, which can be compared with other magnets. magnet interaction. The difference is that it can control the polarity by controlling the switch, and then turn the two ends of the battery over, and then look at the direction of the current. After the reversal, the magnetic pole of the electromagnet is also reversed. It is troublesome to turn over the battery. You can exchange the wires, then return to the rotating magnet, and replace the magnet with the electromagnet just now. After connecting the wires and powering on, the electromagnet will interact with the magnet next to it. When the position of the wire is switched, the polarity of the electromagnet is also reversed at the same time, and it starts to rotate again. As the wire is switched over and over again, the electromagnet will continue to rotate.

In order to increase the magnetic force, put another magnet on the left side of the metal bolt, and the rotation of the electromagnet will be more dynamic under the joint action of the magnets on both sides. Then replace the permanent magnets on both sides with stronger magnetic bending magnets, and replace the winding bolts in the middle with metal circuits. This structure is also called an armature. Then connect the wires and get a circuit. The armature can be regarded as a planar magnet. Under the action of the magnets on both sides, it will rotate to align the two poles.

At the same time, the armature can be kept rotating by switching the wires. For the convenience of not having to switch the circuit manually, a commutator is added to the armature, which is a ring with symmetrical gaps, and then two brushes are added to connect the circuit on both sides of the ring, and the brushes are kept when the commutator rotates Without moving, the spring inside the brush can always keep in contact with the commutator, so that the current can form a loop through the commutator.

When the brush rotates, it switches the contact point when it passes the gap. After the switch, the current flows in the opposite direction, and the polarity of the electromagnet is also switched at the same time, so that the armature keeps rotating. The commutator has been automatically repeating the work of switching wires, and the entire electromagnet will continue to rotate. When the electromagnet that cuts power loses its polarity, the armature also stops rotating.

Ⅳ. Efficiency of motor

The efficiency of the motor refers to the energy utilization efficiency of the motor when converting the input electrical energy into useful mechanical energy output. Expressed as a percentage, it expresses the ratio between the output useful power and the input electric power.

The motor efficiency calculation formula is as follows:

Efficiency = (useful output power / input electric power) × 100%

Useful output power refers to the actual mechanical power generated by the motor, also known as output power. The input electric power refers to the electric energy input to the motor.

Ⅴ. Motor control

1. Stepping motor control:

Pulse control: By applying a specific pulse sequence to the stepper motor, the stepper motor rotates according to a specific step angle.

Micro-step control: On the basis of pulse control, finer angle control can be achieved by controlling subtle current changes.

2. Direct current motor (DC motor) control:

Closed-loop control: Use a feedback device (such as an encoder) to measure the actual speed and position of the motor, and then adjust the operating state of the motor through a control algorithm to achieve more precise control.

Voltage regulation: adjust the input voltage to change the speed of the motor.

Manual control: adjust the speed of the motor through a manual switch or knob.

Pulse width modulation (PWM) control: Control the speed and torque of the motor by adjusting the width and frequency of the pulse.

3. Servo motor control:

Servo control: The servo motor measures the actual speed and position through the feedback device (usually an encoder), and compares it with the set value, and then adjusts the control signal of the motor through the PID (proportional integral differential) control algorithm to achieve precise speed and position. position control.

4. AC motor (AC motor) control:

Closed-loop control: Use feedback devices such as encoders to measure the actual speed and position of the motor, and then control the running state of the motor according to the feedback information.

Frequency conversion control: change the speed and torque of the AC motor by adjusting the frequency and voltage of the AC power supply.

Vector control: Utilize the rotor position and speed information of the motor, and realize high-precision speed and torque control through complex control algorithms.

Ⅵ. Common motor faults

1. Overload and overheating: The motor may be overloaded and overheated when it is running at high load for a long time or the ambient temperature is too high, which may cause the motor to burn or be damaged.

2. Insulation failure: Insulation failure is the most common problem in motor failure. Insulation failures can lead to failure of the insulation between motor windings or between windings and ground, shorting current loops or grounding and causing motor failure.

3. Control system failure: Failure of the motor control system, such as controller failure, sensor failure, etc., may cause the motor to fail to operate as expected.

4. Brush failure: DC motors use brushes to make electrical connections with rotating parts such as rotors. Worn brushes or poor contact can lead to unstable electrical contact between the brushes and rotating parts, affecting the performance and life of the motor.

5. Bearing failure: Bearings support the rotor in the motor and are often subjected to large loads and friction. Long-term operation or poor maintenance may cause bearing wear or damage, which will cause problems such as unstable operation of the motor and noise.

6. Power problem: The voltage stability and current waveform of the motor power supply may affect the performance and stability of the motor, such as voltage fluctuations, frequency deviations, etc.

7. Excitation failure: The excitation system of the DC motor (such as permanent magnet or excitation coil) may have problems such as open circuit, short circuit or demagnetization, which will affect the normal operation of the motor.

8. Phase-to-phase short circuit: In a three-phase motor, a phase-to-phase short circuit may occur, causing the motor to malfunction.

Ⅶ. Classification of motors

1. According to the control mode

Servo Motor: Real-time adjustment of the control signal of the motor through a feedback device, used in applications requiring high-precision position and speed control.

Stepper Motor: The rotation of the motor is controlled by a given sequence of pulses, used in applications that require precise position control.

2. According to the type of rotor

Induction motor: A motor in which torque is generated through the induction effect without electrically connected coils inside the rotor.

Permanent magnet motor: A motor with permanent magnets on the rotor, which can be a DC motor or a synchronous motor.

3. According to the type of power supply

Direct Current Motor (DC Motor): A motor that converts direct current electrical energy into mechanical energy, often used in low power and precise control applications.

Alternating current motor (AC motor): A motor that converts alternating current energy into mechanical energy, and is divided into asynchronous motor and synchronous motor according to the working principle.

4. According to application scenarios

Industrial motors: used in industrial production, such as water pumps, fans, compressors, etc.

Transportation motor: used in vehicles, such as electric vehicles, electric motorcycles, etc.

Household appliance motors: used in household appliances, such as washing machines, refrigerators, air conditioners, etc.

5. According to the working principle

Asynchronous motor: also known as induction motor, it is divided into squirrel-cage asynchronous motor and deep-slot asynchronous motor according to the synchronization of rotor speed and rotating magnetic field.

Synchronous motor: A motor in which the operating speed of the rotor is synchronized with the rotating magnetic field, including permanent magnet synchronous motors and AC excitation synchronous motors.

Ⅷ. Motor maintenance method

Motor maintenance process in professional motor maintenance and repair center: cleaning stator and rotor--replacing carbon brushes or other parts--vacuum class F pressure immersion paint--drying--calibrating dynamic balance.

1. The operating environment should always be kept dry, the surface of the motor should be kept clean, and the air inlet should not be obstructed by dust, fibers, etc.

2. When disassembling the motor, the rotor can be taken out from the shaft extension end or the non-extension end. If it is not necessary to remove the fan, it is more convenient to remove the rotor from the non-shaft end. When pulling the rotor out of the stator, it should prevent damage to the stator winding or insulation.

3. When the thermal protection of the motor operates continuously, it should be found out whether the fault comes from the motor or the overload or the setting value of the protection device is too low, and the fault can be eliminated before it can be put into operation.

4. When replacing the winding, you must write down the form, size, number of turns, wire gauge, etc. of the original winding. When you lose these data, you should ask the manufacturer to change the original design winding at will, which often makes one or more performances of the motor deteriorating, or even unusable.

5. The motor should be well lubricated during operation. Generally, the motor runs for about 5000 hours, that is, the grease should be replenished or replaced. When the bearing is found to be overheated or the lubrication has deteriorated during operation, the hydraulic pressure should replace the grease in time. When replacing the lubricating grease, the old lubricating oil should be removed, and the oil tank of the bearing and bearing cap should be cleaned with gasoline.

Ⅸ.What is the difference between synchronous motor and synchronous motor?

Synchronous motor is a machine whose rotor speed and the speed of the stator magnetic field is equal. Asynchronous motor is a machine whose rotor rotates at the speed less than the synchronous speed. Brushless motor, Variable Reluctance Motor, Switched Reluctance Motor and Hysteresis motor are the synchronous motor.

X.What is the basic introduction of a motor?

A motor is an electrical device that converts electrical energy into mechanical. Motors are designed to produce rotary or linear motion when their electric current and magnetic field interact with each other which is commonly known as electromagnetic interaction – A term coined by Hans Christian Orsted in 1820.