The concept of traction motor, I believe everyone will be unfamiliar with the word "bogie", but in fact, the subway and high-speed rail we often ride are inseparable from traction motor, which can be said to be closely related to our travel. Let's learn about the concept of traction motor.
1 Introduction to the concept of traction motor
The traction motor is the main motor that drives the power shaft of the vehicle and is used for vehicle acceleration and braking.
The stator winding of traction motor is connected with three-phase alternating current, which will produce rotating magnetic field in stator space. The rotor winding will produce induction motor and induction current in the rotating magnetic field, which will make the rotor rotate under the action of electromagnetic force.
There are many types of traction motors, such as DC traction motor, pulse traction motor, single-phase commutator traction motor, AC rotary induction (asynchronous) traction motor, AC synchronous traction motor and linear traction motor.
Traction motor is one of the important parts of electric locomotive, which is installed on the bogie under the car body. When the electric locomotive is in traction state, the traction motor converts electric energy into mechanical energy, which makes the wheelset rotate and drives the locomotive to run.
form
Traction motor is mainly composed of stator and rotor.
Stator includes stator core, stator winding and frame. The stator core is made of silicon steel sheet, which is used to place the stator winding and form the magnetic circuit of the motor; The stator winding is made of copper wire to form the circuit of the motor; The frame is generally made of cast iron or cast steel and is the support of the motor.
The rotor also includes an iron core and a rotating shaft. The rotor core is similar to the stator core, and it is also made of silicon steel sheet, which is a part of the middle magnetic circuit of the motor. The iron core is provided with a slot for placing or pouring windings, which is installed on the rotating shaft.
When working, it rotates with the rotating shaft. Winding is divided into cage and winding. Cage rotor winding is composed of cast aluminum conductor bars or copper bars, and the ends are short-circuited by short-circuit rings. The wound rotor winding is similar to the stator winding. The rotating shaft is made of medium carbon steel, and both ends are supported by bearings to output torque.
In order to ensure the normal operation of traction motor, there is an air gap between stator and rotor, and the size of the air gap has a great influence on the performance of the motor. When the air gap is large, the reluctance is large and the excitation current provided by the power supply is large, which makes the motor run with low power factor; However, the air gap is too small, which will make the assembly difficult, and it is easy to cause the collision of stator and rotor cores in operation. [2]
ask
(1) should have sufficient starting traction and strong overload capacity.
(2) It has good speed regulation performance. Ensure that the EMU has a wide speed range under different driving conditions, and give full play to the power of the traction motor within the speed range. When running forward and backward, its characteristics are as same as possible.
(3) The commutation of 3)DC traction motor is reliable. When operating under the conditions of high current, high voltage, high speed and weak magnetic field, the commutation spark should not exceed the specified spark grade.
(4) All components should have sufficient mechanical strength to ensure the reliable operation of the motor under the worst conditions.
(5) The insulation of the traction motor must have high electrical strength and good moisture-proof and heat-resistant performance, so as to ensure that the motor has sufficient overload capacity and works reliably in its service life.
(6) The structure of traction motor should fully meet the needs of electric train operation and maintenance. For example, the transmission and suspension of the motor should minimize the dynamic effect between the train and the track; Good dust-proof, moisture-proof, rain and snow invasion ability; Easy to repair and replace brushes, etc.
(7) The unit power weight of traction motor must be reduced as much as possible to make full use of electromagnetic materials and structural materials.
Concept of traction motor 2 Suggestions on prolonging the working life of traction motor.
Traction motor is the power source of electric locomotive, and its function on electric locomotive is like human heart, which is a very important part of electric locomotive.
However, electric locomotives need to start, stop and brake frequently when working, so the traction motor will be frequently impacted and vibrated. In addition, although it is stipulated that electric locomotives cannot be overloaded, it is not uncommon for electric locomotives to be overloaded.
Similar "convenient" illegal operations are said to be more or less. Although these illegal operations seem to be nothing, they are actually wasting the expected life of electric locomotives, especially traction motors, which requires daily maintenance and regular maintenance to ensure safety and prolong the service life of traction motors.
If the sound of the traction motor is normal and there is no burnt smell floating out during operation, you only need to pay attention to the surface cleaning of the traction motor and the fastening degree of the fasteners, and you can also check the brushes more patiently.
During regular maintenance, the traction motor should be taken out as a whole and disassembled for inspection to see if there is any serious wear and short circuit. Among them, the commutator and brush of traction motor are the key inspection objects, whether their surfaces are smooth, whether the commutator copper sheet is filled with foreign substances such as carbon powder and so on. If there is a problem, it should be repaired and replaced. If it cannot be handled, please contact the manufacturer.
Concept of traction motor 3 Traffic application of traction motor
Road vehicles
Traditionally, road vehicles (cars, buses and trucks) use diesel and gasoline engines and mechanical or hydraulic transmission systems. In the second half of the 20th century, vehicles with power transmission systems (powered by internal combustion engines, batteries or fuel cells) began to be developed. One advantage of using electric motors is that some types can regenerate energy (i.e. as regenerative braking). By charging the battery pack, it can provide deceleration and improve overall efficiency.
railway
Traditionally, these are series-connected brushed DC motors, which usually run at about 600 volts. The appearance of high-power semiconductors (thyristor and IGBT) makes it possible to use simpler and more reliable AC induction motors (called asynchronous traction motors). Synchronous AC motors are occasionally used, such as TGV in France.
Motor installation
Before the middle of the 20th century, a large motor was usually used to drive multiple driving wheels through connecting rods, which was very similar to the connecting rods used on steam locomotives. For example, Pennsylvania Railroad DD 1, FF 1 and L5 and various Swiss crocodiles. The standard practice now is to provide a traction motor to drive each shaft through a gear driver.
Usually, the traction motor is suspended at three points between the bogie frame and the driven shaft; This is the so-called "suspension traction motor". The problem with this arrangement is that a part of the weight of the motor is not suspended, which increases unnecessary force on the track. Take the famous Pennsylvania Railway GG 1 as an example.
Two motors mounted on the bogie drive each axle through a sleeve driver. General Electric Company has equipped Milwaukee roads with direct-drive "bipolar" electric locomotives. The rotating shaft of the motor is also the shaft of the wheel.
Take the French TGV power car as an example, the motor installed on the frame of the power car drives each axle; The "tripod" driver allows the drive system a little flexibility and allows the truck bogie to pivot. By installing the relatively heavy traction motor directly on the frame of the power car instead of the bogie, better power can be obtained, thus achieving better high-speed operation.