1. KALOL INSTITUTE OF TECHNOLOGY & RESEARCH CENTER

2. BRANCH:-E.E. BANCH:-[A] P.P.T. Sub.:-D.M.T.
ROLL NO.
NAME OF STUDENTS.
ENROIIMENT NO:- 74
Prajapati Mihir V. 76
Rami Bhavin 75
Pomal Raj 99
Zinzuvadiya Dhruv

3. Commutation of the Rotating Loop
Commutation in a Simple Four-Loop DC Machine
Commutation is the process of converting the ac voltages and currents in the rotor of a dc machine to dc voltages and currents at its terminals
A simple 4 loop, 2 pole dc machine is shown here 
The winding’s connections

4. Commutation Process
The machine at time ωt=45°.

5. Commutation of the Rotating Loop
Here, the 1’, 2, 3, and 4’ ends of the loops are under the north pole face, and the 1, 2’, 3’ and 4 ends of the loops are under the south pole face

6. Commutation of the Rotating Loop
This machine has 4 complete loops buried in slots carved in the laminated steel of its rotor
The pole faces of the machine are curved to provide a uniform air-gap width and to give a uniform flux density everywhere under the faces
The 4 loops of this machine are laid into the slots in a special manner
The “unprimed” end of each loop is the outermost wire in each slot, while the “primed” end of each loop is the innermost wire in the slot directly opposite

7. Commutation of the Rotating Loop
A winding Diagram showing interconnections of rotor loops

8. Commutation of the Rotating Loop
The winding’s connections to the machine’s commutator are shown below:
Note : loop 1 stretches between commutator segments a and b, loop 2 stretches between segments b and c, and so forth around the rotor

9. Commutation of the Rotating Loop
The voltages are still built up out of the page for the ends under the north pole face and into the page for the ends under the south pole face
The resulting voltage diagram is shown here:

10. Commutation Process
The machine at time ωt=90°.
the 1’, 2, 3, and 4’ ends of the loops are under the north pole face
the 1, 2’, 3’ and 4 ends of the loops are under the south pole face
so the terminal voltage E=4e

11. Problems with Commutation in Real Machines
Armature reaction
The current though the
Armature conductors set up a magneticfield
surrounding it which
has the following effects
Weakens the main flux
Distorts the main flux
Neutral plan shift