Mechatronics-Learning Note two

From DC Motors, to AC synchronous motors, AC induction motors, to AC motor speed control systems and integrated motors powered by inverters, every step of the motor technology development is accompanied by tremendous progress in the level of human productivity. DC Motor has good start-up performance and speed performance, but it is difficult to create a high-voltage DC engine for long-distance transmission, with the increase of single-machine capacity, DC motor commutation is increasingly difficult. Asynchronous AC motor has simple structure, good steady-state and dynamic characteristics, and is widely used in industrial production.

For the electromechanical system of power exchange, we can introduce the concept of multi-port system and the representation method of Bond graph. A electromechanical system often has multiple subsystems, subsystems are connected to the location is also the power transfer through the place, these positions are called the port, a physical system with one or more ports is called a multi-port system. In order to describe various multi-ports in a unified language, we use power variables (including potential variables E and rheological amount f) and energy variables (including generalized momentum p and generalized displacement Q) to describe various dynamic systems, which can be used to model the physical system. When the two multi-ports are connected together, the potential variable and the rheological amount of the orifice are changed to the same, and the two ports have a common bond. When we use a bond graph to represent interconnected multi-aperture systems, we can see the connection between them more clearly and intuitively.

Modelica simplified DC motor Model

(1) Changing the external connection resistor

The resulting TM and n images with time changes are:

It can be seen that when the motor starts, the speed increases immediately, and in a short time to achieve steady state, reflecting the good starting characteristics of the DC motor; When changing the external resistance value, the motor speed immediately response, and in a very short time to reach the steady state, reflecting the DC motor has good speed regulation performance; increase resistance value, motor speed reduction, Because of the value problem, the descent is not very obvious.

After the motor starts, the electromagnetic torque decreases immediately and approaches 0 in a very short time.

(2) Change the armature end voltage

The resulting TM and n images with time changes are:

After several changes to the armature end voltage value, I found a rule, when the armature end voltage value is enlarged to the previous n times, the motor's steady speed also changed to the previous n times, and the initial value of the electromagnetic torque TM becomes the previous n-1 times. Therefore, it can be seen that by changing the armature terminal voltage to adjust the speed is very convenient and feasible, is the main way to adjust.

Mechatronics-Learning Note two