DC Generators Flashcards
2 types of generator
DC generator (dynamo) - produces DC output
DC alternator - produces AC output which is rectified (converted to DC)
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
The power producing piece of the device - DC gen
The armature
DC generator
Rotating coil and a stationary field
Ac is generated by the rotating armature
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
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
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
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
Field windings
Uses a variable resistor to alter the current to keep the voltage the same
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
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
Right hand rule
First finger = direction of field
Thumb = motion
Second finger = current
