DC Compound motors are popular due do their characteristic of good starting torque and low speed regulation. The are used in pressure blowers, pumps, industrial fan, lathes etc.

1. DC Compound Motor
•Dc Compound motors are utilized in
many industrial application due to its
low speed regulation and high starting
torque characteristic

2. Construction
Stator:
• Generally the outer is stationary part that’s why it is called as
stator which consist of Frame or yoke inside which pole
shoes are bolted projecting Inwards .
• Main fields poles (bigger ones) are always in even number or
in number of pairs
• Inter poles (smaller ones) are also built in even number or in
number of pairs
• On each pole shoe the cropper or aluminum winding is
wound known as field winding which carries the field
current to create static magnetic poles on the stator.
• In all dc machines Filed winding are wound on stators.
DC Compound Motor

3. Construction
Rotor:
• Central rotating part is known as rotor built up of laminated
core having multiple number of slots (axially oriented) on
outer periphery.
• The rotor slots consist of armature conductors are connected
to form close type winding.
• Winding could be wound in “lap” or “wave” patterns
• The complete core is mounted on high grade stainless steel
shaft also keyed to it so as to avoid slipping.
• The shaft is also mounted with commutator ring made up of
multiple number of commutator segments.
• From each commutator segments ends of the armature
winding are connected.
DC Compound Motor

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5. Main Field Pole
Inter-pole
Yoke
Pole Shoe
Armature/ Rotor core
Armature winding
Commutator
Shaft
DC Compound Motor
Shunt Field Winding
Series Field Winding

6. Construction
• Rotor is placed inside the stator separated by small air gap and
free to rotate.
• Rotor is supported by the end cover on both side of the motor
frame by the help of bearings.
• Brushes feeds direct electric current in to the armature winding
pressing on commutator segment.
• Number of brushes are always equal to number of main poles
• Four carbon brushes are in this case of four pole compound
motor
• brushes are always placed at inter polar region.
DC Compound Motor

7. N
S
N
S
Working
• It works on the principle of Lorentz Law, which states
that “the current carrying conductor placed in a
magnetic field experience a force.
• Magnetic Field is produce by the main field poles.
• All main poles consist of two winding set and out of
which one is connected in parallel and another set is
connected in series with the main field winding.
• Field lines emerges radialy inwards from North Pole
and converges in to South Poles placed next to every
North Pole.
DC Compound Motor

8. Working
• Simple representation of field winding.
• Current enters in to first pole form one end and exit
form another terminal from last pole.
DC Compound Motor

9. Working
• Verifying direction of each pole
magnet using right hand thumb
rule.
• Using right hand grip rule
DC Compound Motor

10. Working
• Wiring connection of burses.
• Two brushes are given Positive
voltage and two are given negative.
DC Compound Motor

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12. DC Shunt Motor
Working
• When dc current is feed in to the commutator using brushes.
• The current flows through the armature/rotor winding in such a way that
the coil sides/conductors under the influence of North pole of stator/field
carry current in one direction represented by dot in the diagram.
• The current flows in the coil side/conductor under the influence of south
pole carries current in opposite direction represented by cross in the
diagram.

13. DC Compound Motor

14. Working
• Verifying the direction of force on the
conductors of Left hand side of rotor.
• Applying Fleming left hand rule.
• Index finger – direction of field
• Middle finger – direction of
current
• Thumb – Gives direction of force
DC Compound Motor

15. Working
• Verifying the direction of force on the
conductors of top side of rotor.
• Applying Fleming left hand rule.
• Index finger – direction of field
• Middle finger – direction of current
• Thumb – Gives direction of force
DC Compound Motor

16. Working
• Verifying the direction of force on the
conductors of right side of rotor.
• Applying Fleming left hand rule.
• Index finger – direction of field
• Middle finger – direction of
current
• Thumb – Gives direction of force
DC Compound Motor

17. Working
• Verifying the direction of force on the
conductors of bottom side of rotor.
• Applying Fleming left hand rule.
• Index finger – direction of field
• Middle finger – direction of
current
• Thumb – Gives direction of force
DC Compound Motor

18. DC Compound Motor

19. Working
• After verifying direction of force on all
the conductors, it could be conclude
that the rotor is getting torque in
clock wise direction
DC Compound Motor

20. DC Compound Motor
Connection of windings

21. DC Compound Motor
Characteristics

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