The orthogonal axis is also called the q axis, and the straight axis is also called the d axis. They are actually coordinate axes, not actual axes. In the control of permanent magnet synchronous motor, in order to obtain the control characteristics similar to DC motor, a coordinate system is established on the rotor of the motor, which rotates synchronously with the rotor and takes the direction of rotor magnetic field as the D axis.

The direction perpendicular to the rotor magnetic field is Q axis, and the mathematical model of the motor can be transformed into this coordinate system, so as to realize the decoupling of D axis and Q axis and obtain good control characteristics.

Extended data

Permanent magnet synchronous motor can install the motor on the axle as a whole, forming an integral direct drive system, that is, an axle is a driving unit, which saves a gearbox. The characteristics of permanent magnet synchronous motor mainly include the following points:

1, PMSM itself has high power efficiency and high power factor;

2.PMSM generates less heat, so the motor cooling system has simple structure, small volume and low noise;

3. The system adopts a fully enclosed structure, with no wear and noise of transmission gears, no lubricating oil and no maintenance;

4. The overload current allowed by 4.PMSM is large, and the reliability is significantly improved;

5. The whole transmission system is light in weight, the unsprung weight is lighter than the traditional shaft transmission, and the unit weight power is high;

6. Because there is no gearbox, the bogie system, such as flexible bogie and single axle bogie, can be designed at will, which greatly improves the dynamic performance of the train.

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