Skip to main content

Slip Ring Rotor or Wound Rotor in three phase induction motor

In this type of construction, rotor winding is exactly similar to the stator. The rotor carries a three phase star or delta connected, distributed winding, wound for same number of poles as that of stator. The rotor construction is laminated and slotted. The slots contain the rotor winding. The three ends of three phase winding, available after connecting the winding in star or delta, are permanently connected to the slip rings. The slip rings are mounted on the same shaft. We have seen that slip slip rings are used to connect external stationary circuit to the internal rotating circuit. So in this type of rotor, the external resistances can be added with the help of brushes and slip ring arrangement, in series with each phase of the rotor winding. This arrangement is shown in the Fig. 1. 

Fig. 1  Slip rings or wound rotor

Key point : This way the value of rotor resistance per phase ca be controlled. This helps us to control some of the important characteristics of the motor like starting torque, speed etc.
       In the running condition, the slip rings are shorted. This is possible by connecting a metal collar which gets pushed and connects all the slip rings together, shorting them. At the same time brushes are also lifted from the slip rings. This avoids wear and tear of the brushes due to friction. The possibility of addition of an external resistance in series with the rotor, with the help of slip sings is the main feature of this type of rotor.
 
Comparison of Squirrel Cage and Wound Rotor

Labels:

Comments

Post a Comment

Comment Policy
We’re eager to see your comment. However, Please Keep in mind that all comments are moderated manually by our human reviewers according to our comment policy, and all the links are nofollow. Using Keywords in the name field area is forbidden. Let’s enjoy a personal and evocative conversation.

Popular posts from this blog

Demagnetising and Cross Magnetizing Conductors

The conductors which are responsible for producing demagnetizing and distortion effects are shown in the Fig.1. Fig. 1        The brushes are lying along the new position of MNA which is at angle θ  from GNA. The conductors in the region AOC = BOD = 2θ  at the top and bottom of the armature are carrying current in such a direction as to send the flux in armature from right to left. Thus these conductors are in direct opposition to main field and called demagnetizing armature conductors.         The remaining armature conductors which are lying in the region AOD and BOC carry current in such a direction as to send the flux pointing vertically downwards i.e. at right angles to the main field flux. Hence these conductors are called cross magnetizing armature conductors which will cause distortion in main field flux.        These conductors are shown in the Fig. 2 Fig. 2  ...
Post a Comment
Read more

Characteristics of Separately Excited D.C. Generators

The characteristics is separately excited d.c. generator are divided into two types, 1) Magnetization   and         2) Load characteristics. 1.1 Magnetization or Open Circuit Characteristics         The arrangement to obtain this characteristics is shown in the Fig. 1. Fig. 1  Obtaining O.C.C. of separately excited generator        The rheostat as a potential driver is used to control the field current and the flux. It is varied from zero and is measured on ammeter connected.        E o  = (ΦPNZ) / (60A)        As I f is varied, then Φ change and hence induced e.m.f. E o  also varies. It is measured on voltmeter connected across armature. No Load is connected to machine, hence characteristics are also called no load characteristics which is graph of E o  against field current I f as sho...
Post a Comment
Read more

Armature Voltage Control Method or Rheostatic Control of dc motor

Speed Control of D.C. Shunt Motor (Part2)  2. Armature Voltage Control Method or Rheostatic Control        The speed is directly proportional to the voltage applied across the armature. As the supply voltage is normally constant, the voltage across the armature can be controlled by adding a variable resistance in series with the armature as shown in the Fig. 1. Fig. 1 Rheostat control of shunt motor        The field winding is excited by the normal voltage hence I sh is rated and constant in this method. Initially the reheostat position is minimum and rated voltage gets applied across the armature. So speed is also rated. For a given load, armature current is fixed. So when extra resistance is added in the armature circuit, I a remains same and there is voltage drop across the resistance added ( I a R). Hence voltage across the armature decreases, decreasing the speed below normal value. By varyi...
Post a Comment
Read more