Xijiao 21 autumn "motor and drive" online homework answer sheet (III) [standard answer]

Xi'an Jiaotong 《 Motor and drive 》FAQ（ 3、 ... and ）
Chapter III principle of DC motor
One 、 What are the uses of DC motors ？
DC motor is the equipment to realize the mutual conversion between DC electric energy and machine energy .
A DC motor can be used as a generator , It can also be used as a motor .
Being used as a generator may convert machine energy into direct current , Now it is important to use it as an independent power supply and the excitation power supply of the exchange generator .
Used as an electric motor , Convert direct current energy into machine energy , It is widely used in rolling mills 、 Ship thruster 、 Tram 、 Electric railway traction 、 Blast furnace feeding 、 Papermaking 、 Spin 、 crane 、 Driving of excavation hoist, etc .
Two 、 What is pitch ？
The pitch is the distance between two component edges or commutators connected , It is expressed by the number of virtual slots or the number of commutators . The winding of a DC motor has four pitches ： First pitch y1/ Second pitch y2/ Profiling pitch y/ Commutator pitch yk.
3、 ... and 、 What are the characteristics of single wave winding ？
All N The components at the bottom of the pole are connected in series to form a branch , All S The components at the bottom of the pole are connected in series to form another branch . The number of branches of single wave winding is equal to 2.
When the number and shape of components are symmetrical 、 When the brush is placed in the nominal position of the commutator to align with the core line of the magnetic pole , The maximum potential is felt between the positive and negative brushes . The electric potential of the components short circuited by the brush is the minimum .
The number of brush poles equals the number of poles .
Four 、 Try to describe the excitation method of DC motor
Broadly speaking, the excitation method of motor refers to the method of breaking the magnetic field , The excitation method of electrically excited DC motor refers to the combination of excitation winding and armature winding .
According to the excitation method, the electrically excited DC motor may be divided into ： He encouraged 、 Shunt excitation 、 Series and compound excitation motors .
5、 ... and 、 What are the uses of DC generators ？
The vast majority of modern power systems are three order switching electricity , Most of the general electric parts use exchange electricity directly .
Some parts use exchange electricity , Direct current is also required .
There are two ways to get direct current ： One is to use electronic rectifier installation to convert exchange electricity into direct current ; The other is to use other power equipment to drive the DC generator to generate DC .
With the development of Power Electronics Technology , The first method is more and more widely used . But in most mobile units , Like a plane 、 train 、 Ships and so on still make extensive use of DC generators .
6、 ... and 、 What are the features of solid machines ？ Aopeng Xijiao
Armature voltage 、 The air gap magnetic flux per pole is rated 、 The machine feature when the armature circuit is not connected in series with resistance is called the solid machine feature of DC motor .
7、 ... and 、 What role does the commutator play in the DC motor ？
In DC generator , The commutator acts as a rectifier , That is, the exchange current in the armature winding is rectified to direct current , Output at both ends of positive and negative brushes . In DC motors , The commutator acts as an inverter , That is to say, the DC current in the external circuit of the brush is inverted into the exchange current through the commutator and input into the armature element .