Prepared by: Braj Bihari B.Tech(IT)

DC MACHINES

DC CONSTRUCTION

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Field System

Armature

Armature Cont..

Armature Windings

Armature winding cont..

Commutator

Commutator and Brushes

Principle of Operation of DC Generator and DC Motor

Principle of Operation

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DC GENERATOR OPERATION

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DC MOTOR

DC MOTOR

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EMF or Armature Voltage Equation

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Torque

Types of DC Motor

Classification of DC Machines

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Speed and Torque Characteristics of a DC Motor

Separately Excited Equations

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Torque- Speed Characteristics

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Selection of DC Motor for Particular Applications

Separately Excited Motors

1. Accurate Speed2. Speed variation is required from very low

value to high value.3. Used in steel rolling mills, paper machines,

diesel-electric propulsion of ships.

Shunt Motors

It is constant speed motor so it used for:

1. Where the speed between no load to full load has to be maintained almost constant.

2. Where it is required to drive the load at various speeds and any one of the speed is required to be maintained almost constant for a relatively long period.

Series Motors

It is variable speed motor:

1. Where high torque is required at the time of starting to accelerate heavy loads quickly.

2. Where the load is subjected to heavy fluctuations and speed is required to be adjusted automatically.

3. Most suitable for electric traction, cranes, elevators, vacuum cleaners, air drives, sewing machines, fans and air compressors.

Compound Motors

1. Where high torque is required at the time of starting and where the load may be thrown off suddenly.

2. Where the load is subjected to heavy fluctuations.

3. Best suited for punching and shearing machines, rolling mills, lifts and mine-hoists.

Applications

Applications

The d.c. machine can operate as either a motor or a generator, at present its use as a generator is limited because of the widespread use of ac power.

Large d.c. motors are used in machine tools, printing presses, fans, pumps, cranes, paper mill, traction, textile

mills and so forth.

Small d.c. machines (fractional horsepower rating) are used primarily as control device-such as tacho-generators

for speed sensing and servomotors for position and tracking.

Paper and Steel Mills

Steel MillsSteel Mills

Mining and Machine Tools

Robots and Petrochemicals

Thanks