What is a pulse current traction motor? Pulse current traction motor refers to a series excitation traction motor working under pulsating voltage. Traction motor includes traction motor, traction generator and auxiliary motor. The following is about what a pulse current traction motor is.
What is a pulse traction motor? 1 Series-excited pulse traction motor refers to the series-excited traction motor working under pulsating voltage. Its structure is similar to the general DC traction motor. In the rectifier electric locomotive, the voltage applied to the traction motor has a larger AC component besides the DC component. The AC component of the voltage will cause the motor to heat up and the rectification effect will become worse. Reactors are usually connected in series in the main pole winding and armature winding to reduce current pulsation.
At the same time, a fixed shunt resistor is connected in parallel with the main pole winding to bypass the AC component. In the design of traction motor, it is also necessary to minimize the influence of transformer potential, reactance potential and rectification potential caused by pulsating current on rectification.
Series pulse current traction motor
Series-excited traction motor working under pulsating voltage
Traction motor refers to the motor used to drive the moving wheels on locomotive and rolling stock. According to the nature of power supply, it can be divided into DC, pulse and AC. DC locomotive adopts DC traction motor, and rectifier electric locomotive adopts pulse traction motor. Usually, DC traction motor and pulse traction motor adopt series excitation type, because series excitation type has good traction characteristics.
Alternating current can be divided into single-phase commutator traction motor and three-phase asynchronous traction motor. The former is used for direct AC electric locomotives, and the latter is used for AC -DC- AC drive electric locomotives or diesel locomotives. Due to the influence of space, vibration and climate, the operating conditions of traction motors are far worse than those of ordinary motors, and there are many special requirements in design and structure.
Traction motors can be divided into shaft-holding traction motors and frame-supported traction motors according to different suspension modes. The former is supported on the moving shaft by the shaft support bearing.
The other side is hung on the frame with a spring, which is used for medium-speed locomotives, and the latter are all hung on the frame. Besides gears, elastic elements are added to transfer torque between the motor and the moving shaft, reducing impact vibration, which is suitable for high-speed locomotives.
What is the development of pulse traction motor 2?
As the prime mover of vehicle driving, AC variable frequency traction motor is an advanced traction technology developed in the 1980s. It has developed rapidly in Germany, Japan, France and other economically developed countries with its remarkable excellent characteristics, and soon replaced the traditional DC traction motor.
In order to solve the steering problem of DC and pulse traction motors, some countries have been using thyristor commutatorless traction motors and three-phase AC asynchronous variable frequency traction motors, and are experimenting with maglev high-speed vehicles powered by linear asynchronous motors.
Thyristor commutatorless traction motor consists of a synchronous motor and a group of thyristor inverters. The commutator and carbon brush structure of DC traction motor are replaced by thyristor and rotor position detector. This motor has the advantages of DC motor without the difficulty of "commutation".
However, the thyristor and its control system are quite complex, so the electronic components directly affect the running reliability of the motor. Three-phase AC asynchronous variable frequency traction motor is an ideal traction motor with simple structure, reliable operation and low cost. However, due to the need of variable frequency speed regulation, its development and application were once limited.
In 1960s, the development of high-power thyristor frequency conversion device made asynchronous motor realize frequency conversion speed regulation. Since 2 1 century, many locomotives and emus in various countries have adopted three-phase AC asynchronous variable frequency traction motors. The Federal Republic of Germany and Japan use linear asynchronous motors on the tested maglev high-speed vehicles.
Its primary winding is laid on the ground guide rail, powered by the ground frequency conversion power supply, generating a traveling wave magnetic field. The speed of maglev high-speed vehicle can be changed by adjusting the frequency of power supply. The secondary winding is an induction plate installed on the frame.
The interaction between the primary traveling wave magnetic field and the secondary induced current not only produces the thrust to push the vehicle forward, but also produces the magnetic pull of the suspended vehicle, which plays the role of dynamic braking under braking conditions.
What is the principle of pulse traction motor 3?
Traction motors are usually powered by frequency converters. Higher requirements are put forward for the function and performance index of test equipment:
1, which requires that the test equipment has a wide bandwidth and can obtain high measurement accuracy in a wide frequency range;
2. The fundamental frequency of some tests may be lower than 5Hz, which makes it impossible for conventional measuring instruments to stably read;
3. The switching frequency of inverter is low, the harmonic content is rich, the signal is not a strict periodic signal, and Fourier transform needs a long time window.
In order to correctly measure the effective value of the fundamental voltage output by the traction inverter, attention must be paid to:
1, using the correct frequency conversion electric quantity measuring device. Voltage and current sensors and instruments should have reasonable bandwidth, correct measurement mode (fundamental rms mode), and meet the accuracy level requirements at the output frequency.
2. On the premise that the switching frequency (carrier frequency) is high enough (at least 20 times greater than the fundamental frequency), the effective value of the fundamental wave displayed by the traction inverter (close to the theoretical value) is consistent with the measured results. In fact, the switching frequency of traction inverter is often low, generally lower than 1KHz, while the fundamental frequency is high, so this condition is not met.
3. To measure the effective value of fundamental wave accurately and stably, the premise is that the output of frequency converter is a periodic signal (Fourier transform is aimed at periodic signals). In fact, because the switching frequency of traction inverter is low, when the switching frequency is not an integer multiple of the fundamental frequency, its output signal is not a periodic signal.
For example, the switching frequency is 500Hz and the fundamental frequency is 60Hz. If the current basic cycle starts at the beginning of the 0th pulse, it will end at 1/3 of the 9th pulse, and the next basic cycle will start at 1/3 of the 9th pulse. Obviously, these two fundamental periods are not the same signal, that is, the inverter output is not a periodic signal.