Hello friends, today I am going to tell you Selecting the number of poles of the D.C. Machine/Motors, What is a pole in DC machine/Motors: If you also want to know, then keep reading this article completely.
What is a pole in DC machine/Motors
Selecting the number of poles of the D.C. Machine: A DC The number of poles used in a machine is important in both magnetic and electric circuits. To select the number of poles, assume that the diameter D, length L, specific magnet, and electric loading of the machine is constant and the number of poles varies.
1. Frequency- The frequency of flux change in the air space is f = pn/2. Hence the number of poles is kept more so that the frequency remains high. The frequency of magnetic flux change should not be so high as to cause excessive iron losses in the armature teeth and core, so the value of frequency is kept between 25 to 50 Hz, which can be higher in small machines.
2. Weight of Iron Parts – The number of poles also affects other parts. If the machine is designed for 4 poles, the flux per pole will be t/4 and the flux in the armature core and yoke section will be t/8.
The weight of the machine depends on the number of poles. It can be understood as follows.
(i) The cross-section area of the yoke decreases with the increase in the number of poles.
(ii) The weight of iron in the armature core decreases as the number of poles increases.
(iii) By taking more poles, the diameter of the machine decreases.
Based on the above points, it can be concluded that keeping more poles reduces the total iron weight of the machine.
3. Overall Size of Machine- As the number of poles increases, the length of the pole decreases, and the overall outer diameter of the machine decreases. As the number of poles increases, the overhang in the armature winding decreases, which reduces the overall length of the armature. Increasing the number of poles reduces the overall size of the machine.
4. Weight of Copper- As the number of poles increases, the pole pitch decreases, which leads to a reduction in copper load.
More number of poles in the machine reduces the amount of armature copper and also reduces the overhang portion of the winding. Thus the length of the machine is reduced. As the number of poles increases, the load on the field copper also decreases. The number of poles is inversely proportional to the magnetic carrying force (MMF). The magnetic carrying force of 2 poles is twice the magnetic carrying force of 4 poles, so the mean length of a turn in 2 poles is more than the mean length of a 4 pole turn, due to which copper takes more in the area of 2 poles as shown in the figure. have been shown.
5. Labor Charge – The remuneration increases with the increase in the number of poles because more field coils have to be made due to more number of poles and more armature coils have to be installed on the commutator segment, as well as for assembling and insulating the segments. work increases.
6. Length of Commutator- The number of brushes in lap wound armature is equal to the number of poles and only two brushes are used in wave wound armature. The current collected by each brush arm in a DC machine is inversely proportional to the number of poles, i.e., the area of the brushes in each arm decreases or the length of the brushes is reduced, resulting in a decrease in the length of the commutator. She goes.
7. Flash Over Between Brushes – By increasing the number of poles, the number of brushes on the commutator segment increases, so the distance between brushes for the same diameter decreases. This results in an increased tendency of flashover between the brushes.
- Read more: what is a DC generator?
- Read more: Types of Losses in Transformer?
what did you learn today:-
Friends, today you learned Selecting the number of poles of the D.C. Machine/Motors, What is a pole in DC machine/Motors. If you liked the information given by me, then you can share it with your friends and if you have any question or suggestion in your mind, then you can tell by commenting below.