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Flashcards in DC Generators Deck (12)
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1

2 types of generator

DC generator (dynamo) - produces DC output

DC alternator - produces AC output which is rectified (converted to DC)

2

Faradays law - the amount of EMF depends on

Strength of the magnetic field
Speed of the conductor relative to the field
Angle at which conductors cuts the field
Length of the conductor in the field

3

The power producing piece of the device - DC gen

The armature

4

DC generator

Rotating coil and a stationary field

Ac is generated by the rotating armature

5

Spilt ring commutator

Commutator and brushes are used to extract DC from the AC generated in the coil

Reverses the circuit between the coil and the external circuit
Only allows the output voltage to fluctuate between 0 and max
Causes the flow off the brushes to flow in 1 direction

6

Adv and disadv of DC gen

Can be used as a starter motor and a generator in some turbine a/c - saves weight

Disadv - poor output at low RPM - due to the commutator sparks at the carbon brushing

7

DC alternator

Rotating field with a stationary armature

As the rotor turns the rotating field induces on alternating in the armature - polarity of the magnetic field alternates as the magnet rotates through the field

As alternating voltage = alternating current - needs to convert it to DC - done by a rectifier fitted in the body of the alternator

8

Carbon pile voltage regulator

Solenoid makes the carbon plates more compact/loosen to increase/decrease resistance and regulate the amount of output from the generator to maintain a constant voltage

Only controls a shunt volt generator circuit

9

Field windings

Uses a variable resistor to alter the current to keep the voltage the same

10

Shunt wound generator

Field coil is in parallel with the armature - allows us to have control over them- can control the current going through the coil - allows constant voltage

11

Use of ground power

A/c system is isolated when it is connected - can’t mix ground power with a/c power

Automatically kicks out a/c battery - prevents it using the a/c battery if is the dominant voltage

12

Right hand rule

First finger = direction of field
Thumb = motion
Second finger = current