Dc Synchronous Machines
- Submitted by: rahulpetrocrat
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- Category: Science
- Date Submitted: 11/12/2010 02:05 PM
- Pages: 7
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DC Machines:
Stator
Main Parts:
• • • • A stationary stator : carries field poles or field coils Rotor: carries armature or armature windings Commutator: for ac to dc conversion Brushes : slides on commutator and collect or supply dc current
DC MACHINES
• The field poles, which produce the needed flux, are mounted on the stator and carry windings called field windings or field coils • The armature core, which carries the armature windings, is generally on the rotor and is made of sheet-steel laminations. • The commutator is made of hard-drawn copper segments insulated from one another by mica. • armature windings are connected to the commutator segments over which the carbon brushes slide and serve as leads for electrical connection. The armature winding is the load-carrying winding.
Electromagnetic Energy Conversion:
1. When armature conductors move in a magnetic field (produced by the current in stator field winding), voltage is induced in the armature conductors. When current carrying armature conductors are placed in a magnetic field (produced by the current in stator field winding), the armature conductors experience a mechanical force.
2.
These two effects occur simultaneously in a DC machine whenever energy conversion takes place from electrical to mechanical or vice versa.
Electromagnetic Force, f
f=Bli, where B, f and i are mutually perpendicular.
Motional Voltage, e
e=Blv, where B, v and e are mutually perpendicular.
Wire loop rotating in a magnetic field.
6
Elementary DC Generator with Commutator and Brushes:
Brush
7
Force on a current-carrying wire in a magnetic field.
8
Flux compression and resulting force.
9
Commutator and Brushes on DC Machine
To keep the torque ( or current) on a DC machine from reversing every time the coil moves through the plane perpendicular to the magnetic field, a split-ring device called a commutator is used to reverse the current at that point. The...
Stator
Main Parts:
• • • • A stationary stator : carries field poles or field coils Rotor: carries armature or armature windings Commutator: for ac to dc conversion Brushes : slides on commutator and collect or supply dc current
DC MACHINES
• The field poles, which produce the needed flux, are mounted on the stator and carry windings called field windings or field coils • The armature core, which carries the armature windings, is generally on the rotor and is made of sheet-steel laminations. • The commutator is made of hard-drawn copper segments insulated from one another by mica. • armature windings are connected to the commutator segments over which the carbon brushes slide and serve as leads for electrical connection. The armature winding is the load-carrying winding.
Electromagnetic Energy Conversion:
1. When armature conductors move in a magnetic field (produced by the current in stator field winding), voltage is induced in the armature conductors. When current carrying armature conductors are placed in a magnetic field (produced by the current in stator field winding), the armature conductors experience a mechanical force.
2.
These two effects occur simultaneously in a DC machine whenever energy conversion takes place from electrical to mechanical or vice versa.
Electromagnetic Force, f
f=Bli, where B, f and i are mutually perpendicular.
Motional Voltage, e
e=Blv, where B, v and e are mutually perpendicular.
Wire loop rotating in a magnetic field.
6
Elementary DC Generator with Commutator and Brushes:
Brush
7
Force on a current-carrying wire in a magnetic field.
8
Flux compression and resulting force.
9
Commutator and Brushes on DC Machine
To keep the torque ( or current) on a DC machine from reversing every time the coil moves through the plane perpendicular to the magnetic field, a split-ring device called a commutator is used to reverse the current at that point. The...