Answer sheet for online assignment of "motor and drive" of Xijiao 21 autumn (IV) [standard answer]

Xi'an Jiaotong 《 Motor and drive 》FAQ（ Four ）
Chapter IV operation of separately excited DC motor
One 、 Directly start the achievements encountered
The DC motor is controlled by the original motion condition , Turn on the power , Decelerate to a certain task speed , This process is called startup .
Request to start ：
High torque , Fast start , Improve productivity ;
The current should not be too large , So as not to persecute the power supply and motor ;
The equipment is simple , Easy to control .
When the DC motor is directly connected to the rated voltage for starting , There will be certain achievements .
Two 、 What are the characteristics of armature series resistance speed regulation ？
The problem of armature series resistance speed regulation ： Consume large 、 The firmness of rotating speed becomes worse 、 It is difficult to realize stepless speed regulation .
The advantage is that the equipment is simple , Low investment cost . It is suitable for those who do not require high speed regulation function 、 On small motors .
The speed regulation method belongs to constant torque speed regulation .
3、 ... and 、 Field weakening speed regulation of separately excited DC motor
Keep the system voltage stable at the rated value , The armature circuit is not connected in series with resistance , When the load torque driven by the motor is not too large , Falling flux , You can get the rest of the speed difference .
The speed at which the motor operates without the characteristics of the machine is called the base speed .
After connecting the armature circuit with resistance in series , The rotational speed of the system will be lower than the base speed , The speed regulation bias of the speed regulation method is from base speed to up regulation .
With constant power load , Use this method to adjust the speed , The armature current will remain stable .
Four 、 Speed regulation method
The motor operates at the rated armature current , Most efficient and economical . In the process of speed regulation , Keep armature current stable at rated value , It is the fantasy state of speed regulation .
When the motor is running , The actual armature current depends on the speed regulation method of the motor and the load .
In some speed regulation method , Maintain armature current Ia=IN Stable , If the electromagnetic torque of the motor is also constant and stable , This speed regulation method is called constant torque speed regulation method .
In some speed regulation method , Maintain armature current Ia=IN Stable , If the electromagnetic power of the motor is constant and stable , This speed regulation method is called constant power speed regulation method .
5、 ... and 、 Forward electric operation of aopeng Xijiao
The system operates at I Quadrant time , Electromagnetic torque T>0, speed n>0, The electromagnetic torque and speed are in the same direction , The electromagnetic torque is the drag torque , This operation condition is called forward electric operation .
In case of positive electric operation , The electric power that the motor sends power to the motor , Feel through electromagnetism （ Generating force ） Convert to machine power . The whole process is accompanied by the electric consumption and no-load consumption of the armature circuit .