what is dc motor：
The structure of dc motor.
Basic structure: divided into two parts: stator and rotor.Note: do not confuse the commutator with the commutator.The stator includes: main magnetic pole, stand, commutating pole, brush device, etc.Rotor includes: armature iron core, armature (shu) winding, commutator, shaft and fan, etc.The rotor consists of an armature iron core, armature, commutator and other devices, and the components in the structure are described in detail.
1. Armature core part: its function is to lay the armature winding and the end flux, in order to reduce the eddy current loss and hysteresis loss in the armature iron core during the working of the motor.
2. Armature part: the action is the attack electromagnetic torque and induction electromotive force, and carries on the energy transformation.Armature windings have many coils or fiberglass coated flat steel copper wire or strength enameled wire.
3. The commutator is also called the commutator, in dc motor, its role is to brush on the current of dc power supply into the communication of the current in the armature winding, electromagnetic torque tend to be stable, in direct current generator, it will communicate the armature winding electromotive force transformation for the brush on the output dc electromotive force.The commutator is insulated by a mica between the cylinders of many pieces, and the armature windings are separated by two ends of each coil.Dc generator in the role of the commutator of the armature winding is alternating electric thermal transformation between brush dc electromotive force, through in the load current, direct current generator output electrical power to the load, also must have a current through the armature coil.It interacts with the magnetic field and has an electromagnetic torque, which tends to be contrary to the generator. The original idea simply inhibits this magnetic field torque to change the armature.Therefore, the power of the generator to the load output power, from the original idea to output the mechanical power, the end of the dc generator to transform the mechanical energy into the electric energy.
Classification of dc motor.
The excitation method of dc motor refers to the problem of how to power the excitation winding and generate the excitation flux.According to different excitation modes, dc motor can be divided into the following types:
1.He excited the dc motor.
The excitation winding has no connection with the armature winding, and the dc motor that is supplied by other dc power sources to the excitation winding is referred to as the dc motor.In the figure, M represents the motor. If it is a generator, G is used.Permanent magnet dc motor can also be regarded as his motor.
2.Shunt dc motor.
The excitation winding of dc motor is parallel to the armature winding.As a shunt dynamo, it is the terminal voltage of the motor itself to supply the excitation winding.As a shunt motor, the excitation winding and the armature share the same power supply, which is the same as that of the dc motor.
3.Series dc motor.
The excitation winding of the series dc motor is connected with the armature winding and then connected to dc power supply. The excitation current of this dc motor is the armature current.
4.Compound dc motor.
Compound dc motor has shunt excitation and series excitation winding.If the magnetic flux generated by series winding is the same as that of the excitation winding, it is called cumulative compound excitation.If two magnetic potential directions are opposite, they are called differential compounding.
Dc motors with different excitation modes have different characteristics.Generally, the main excitation modes of dc motor are shunt, series and compound, and the main excitation modes of dc generator are his excitation, shunt and compound.
The characteristics of
(1) good speed regulation performance.The so-called "speed regulation performance" means that the motor changes the speed of the motor manually under certain load conditions.Direct current motor can achieve uniform, smooth stepless speed regulation under heavy load conditions, and the range of speed regulation is wide.
(2) large starting torque.The speed adjustment can be realized evenly and economically.Therefore, all machines that start under heavy load or require uniform speed adjustment, such as large reversible rolling mills, winches, electric locomotives, electric cars, etc., are all used.
There are no scrubbing classes
1. Brushless dc motor: brushless dc motor is used to exchange the stator and rotor of ordinary dc motor.The rotor is a permanent magnet which generates an air gap flux: the stator is an armature and is composed of a polyphase winding.In structure, it is similar to a permanent magnet synchronous motor.
The structure of brushless dc motor stator is the same as that of ordinary synchronous motor or induction motor.The polyphase winding is embedded in the iron core (three phase, four phase, five phases).The winding can be connected to a star or a triangle, and connected with each power tube of the inverter to make a reasonable change.The rotor is made of rare earth materials with high coercivity and high residual magnetic density, such as samarium cobalt or neodymium iron boron, because of the different position of magnetic materials in the magnetic pole.It can be divided into surface magnetic pole, embedded magnetic pole and ring pole.Since the motor is permanent magnet motor, the brushless dc motor is also known as permanent magnet brushless dc motor.
2. A brush dc motor: there are two brush brush motor (copper brush or carbon brush) is directly by insulating seat fixed on the motor back cover will be introduced to the power supply is negative on the commutation of the rotor, and the phase switcher connected on the rotor coil, 3 coil constant alternating polarity with fixed on shell form 2 magnet force and rolling.Because the inverter is fixed with the rotor, the brush is fixed with the shell (stator), and the constant friction between the brush and the inverter produces a lot of resistance and heat.So the efficiency of brushless motor is very large.But it also has the advantages of simple manufacturing and low cost.
The start of dc motor.
Due to the small motor armature loop resistor and inductor, and turn the body has a certain mechanical inertia, so when the motor after turning on the power supply, the start of the starter armature speed and corresponding counter electromotive force is small, large starting current.The maximum rated current is 15 ~ 20 times.This current will cause the power grid to be disturbed, the unit is subjected to mechanical shock, the commutator sparks.Therefore, the direct switching start is only applicable to motors with no more than 4 kilowatts of power (starting current is 6 ~ 8 times of rated current).In order to limit the starting current, the variable resistor, which is specially designed in the armature loop, is usually connected to the circuit. The principle wiring is shown in figure 1.In the process of starting up, with the increasing of the speed, each segment resistance is short, and the starting current is limited to a certain allowable value.This kind of starting method is called series resistance starting, it is very simple, the equipment is portable, and it is widely used in all kinds of small and small dc motor.However, due to the high energy consumption in the starting process, it is not suitable for the motors with regular starting and large dc motor.However, for some special needs, such as the urban trams often start, in order to simplify the equipment, reduce weight and operation and maintenance convenience, it is usually used to start the series resistance.
For dc motor with large capacity, the voltage starting is usually adopted.That is, a single adjustable dc power supply can supply power to the motor armature, and the control voltage can both smooth the motor and speed the adjustment.The power supply device of this method is more complicated.
Fault treatment of dc motor.
Common faults of dc motor and its causes.
One, cannot start.
1 2, motor, motor power supply voltage power line break loose or joint 3, armature winding open 4, brush and commutator poor contact 5, motor power switch damage or poor contact 6, the armature is stuck
Second, the speed is slow.
1, brush winding by 2, 3 in the armature winding short-circuit components, brush wear serious, causes the brush and commutator poor contact, and brush spring pressure is too small, bearing wear, or lack of lubricating oil 4 5, low power supply voltage, or battery use time is too long
3. The power supply voltage is too high, the stator magnetic field is weak and the motor load is too light.
4. The power of the machine shell is 1, the armature winding is connected to the ground 2, the stator excitation winding is connected to the ground 3, the commutator is connected to the ground 4, the electric brush rod passes to the ground 5, the electric brush seat of the phase changing device is connected to the ground.
5, 1, excessive sparking brush brush is not located in the position of the neutral line 2, brush and commutator interface is too small, brush current density too big 3, short circuit between commutator segment 4, commutator surface serious bumpy 5 between commutator segment of mica protrusions. 6, brush material is not pure, hard cuttings or other impurities 7, brush by 8 to 9, brush brush winding winding, has a short circuit, brush winding unit 10 reverse connection of the unit
6. The commutator produces spark 1, the brush is far away from the neutral line 2, the commutator is seriously concave and concave;Make the brush and commutator poor contact between 3, commutator segment 4, severe armature winding open circuit potential difference is too large, or serious short circuit 5, armature winding voltage is too high, to 6, motor motor speed is too high
7. Sometimes it can be started, sometimes it can't start 1, the armature winding has broken unit 2, the power switch is in bad contact, the commutator ellipse is large, and the brush is too short.
1. The rotor of the motor is bent 2, the armature slot is protruded out of the groove, and the end of the armature winding is damaged, and the bearing is damaged, causing the armature to be swept.
9. The armature makes a large hiss 1, the brush is too hard 2, the brush spring pressure is too big.
10. There are load running time fuse firing 1, the motor power supply voltage too high 2, the brush is not in neutral position 3, armature winding or excitation winding short circuit.
11, 1, armature winding no-load fuse when serious break 2, armature winding by 3, brush through 5 to 4, motor bearing is too tight, severe field winding short circuit 6, brush away from the neutral position
12. The mica in the commutator segment of the electric brush will be made out to the surface of the commutator, the surface of the commutator shall be uneven, the size of the brush shall be less than 4, and the clearance of the bearing shall be large.
Thirteen, severe fever 1, armature winding shell be affected with damp be affected with damp, and motor heat dissipation is not good 2, electric machine long time overload running 3, bearing lubrication is not good, the lack of lubricating oil fourteen, severe fever 1, armature winding armature winding be affected with damp be affected with damp 2, 3 motor overload is serious, the armature winding short circuit unit
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