Generator fundamentals 1
-
Upload
walid-salama -
Category
Education
-
view
505 -
download
3
description
Transcript of Generator fundamentals 1
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
Generator Fundamentals and the
Theory of Magnetism
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
Ampere’s Law expresses that whenever there is an electric current of any kind, a magnetic field is created and lines of flux encircle the current.
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
Magnetic field or flux established by current flowing through a coil or wire, obey the Right
Hand Rule.
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
If the thumb of the right hand is pointed in the direction of current flow, the finger will curl in the
direction of the magnetic flux.
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
What is the direction of the magnetic field around the wire?
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
The concept of magnetomotive force, or MMF is central to understanding the operation of a
generator.
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
MMF can be thought of as the strength of the magnet.
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
What determines the strength of MMF of a magnet?
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
The number of coil turns (N)
and
The magnitude of current (I)
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
The point at which lines of flux leave the magnet is called the North Pole.
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
The point at which lines of flux enter the magnet is called the South Pole.
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!TB1-03
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
Indicates that current is flowing into the page
Indicates that current is flowing out of the page
Draw the magnetic lines of flux.TB1-03
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
Indicates that current is flowing into the page
Indicates that current is flowing out of the page
Draw the magnetic lines of flux.TB1-03
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
Where is the North Pole located?
N
S
TB1-03
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
What happens if you increase current?
N
S
TB1-03
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
The magnetic field that is produced around a magnet causes a certain amount of flux to exist
around the same path.
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
The amount of flux is dependent upon the magnetic field strength and the permeability of
the material through which the flux passes.
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
In the generator, flux interactions occur in the armature windings located in the stationary part
of the machine (stator).
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
This voltage is referred to as generated or terminal voltage.
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
Maximum generated voltage occurs when the rotating magnetic field cuts at a 90 o angle.
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
Label the parts of the generator.
TB1-04
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
Where is the stator?
Stator
Stator
TB1-04
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
Where is the rotor?
Stator
Stator
Rotor
TB1-04
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
What is the space called between the rotor and the stator?
Stator
Stator
Rotor
TB1-04
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
Air Gap
Stator
Stator
Rotor
TB1-04
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
Draw the magnetic lines of flux.
N
S
TB1-04
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
N
S
TB1-04
Why did the flux go into the stator?
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
N
S
TB1-04
Because the stator is made of iron, it has less resistance than air.
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
N
S
TB1-04
What happens to the flux as the rotor turns?
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
The flux will rotate with the rotor and still pass through the stator.
N
S
TB1-04
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
N
S
TB1-04
What would happen if the flux inside the core became to large?
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
The core would eventually saturate and magnetic lines of flux would go outside the stator core. The
flux outside of the core will induce a voltage into the stator frame thus creating a current.
N
S
TB1-04
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
The current will cause excessive heating that will eventually damage the generator!
N
S
TB1-04
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
For Generator Action (Voltage) to occur, three conditions are required to be met to
induce a voltage:
Generating Electricity
Conductor
Magnetic Field
Relative Motion
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
• The Conductor is a length of wire wrapped around the metal ring.
Generating Electricity
The Magnetic Field is produced by a battery and connected to a rotating metal bar.
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
• As DC flows through the metal bar, a magnetic field is formed creating a magnet.
• The magnet has a North and South Pole.
Generating Electricity
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
• Rotating the magnet so that the field cuts the conductor causes relative motion between the conductor and the field.
• Each time a Pole cuts the conductor, a voltage is induced.
Generating Electricity
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
• Assumption: Every time the North Pole passes by the conductor, a maximum positive (+) voltage is induced into the conductor.
Generating Electricity
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
Generating Electricity
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
Operation of a Simple Generator
• DC is applied to the generator rotor from an external source through slip rings and carbon brushes.
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
Operation of a Simple Generator
• Slip Rings are made from copper, brass or steel and are insulated from the generator shaft.
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
Operation of a Simple Generator
• Larger generators will use steel slip rings to compensate for large amounts of heat that can be generated.
• Steel slip rings will have a groove cut into the face for cooling and for proper bush wear.
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
Operation of a Simple Generator
• Smaller machines will use copper or brass because they are lighter and there is not as much heat.
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
Operation of a Simple Generator
• Brushes are made of a carbon composite.
• Carbon is chosen because it is an excellent conductor, cheaper to manufacture, and easier to work with.
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
• Current to the rotor is supplied by a DC power source. This current is called Excitation Current.
• This current flows through the brushes, slip rings, closed loop, and back to the source.
Operation of a Simple Generator
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
Operation of a Simple Generator
What is the stationary components of the generator called? __________________
What is the rotating portion called? __________________
What makes the electrical contact between the excitation supply and the rotor? _________________
Excitation supply provides what type of current? ______________
Stator
Rotor
Slip Rings and Brushes
DC
TB1-05
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
Operation of a Simple Generator
The armature is the part of the generator where ________________________ .
Slip Rings are made of what? ______________________
Slip Rings may have a ________
that is used for what? ___________________________
A North Pole will always produce a _____________________ ?
Current and Voltage are induced
Steel, Copper, or Brass
Groove
Cooling and Equal Current Distribution
Max Positive (+)
TB1-05.1
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
Generator Frequency
Speed of the Rotor
Number of Rotor Poles
There are two factors that will determine frequency:
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
Generator Frequency
Frequency = NP /120
where
N = rotor speed in rpm
P = number of rotor poles
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
Draw the AC WaveformIn
duce
d V
olta
ge
TB1-06
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
Draw the AC Waveform
TB1-06
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
• The simple generator is only a single-phase generator because it only has one set of windings in the stator.
• Most power generators have 3 sets of windings that produce 3 distinct outputs that are 120o apart.
Three Phase AC Generation
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
• Each winding or phase is actually several windings connected in series.
• Windings connected in series increase the voltage in each phase. This is desirable to limit the strength of the excitation current.
Three Phase AC Generation
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
• The same assumptions apply for the 3-phase generator that applied to the single-phase generator: “A North Pole under the winding will produce a maximum Positive (+) voltage”.
Three Phase AC Generation
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
Most generators are connected in “WYE or Star”.
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
In the WYE connection, the three neutral connections are connected together and the three
line terminals are connected to the system.
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
This connection can be used to detect ground faults within the armature windings of the generator.
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
• The equipment used in 3-phase systems has many advantages over that employed in single-phase service.
3-Phase AC Systems
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
• Advantages include:
• reduced size,
• increased reliability of transmission, and
• reduced cost because of machinery size and less conductors.
3-Phase AC Systems
TB1-07
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
Types of Power
The output capacity of a generator is expressed in MVA, or Mega-Volt-Amperes.
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
Types of Power
However, the power systems engineer defines 3 types of power: Real Power, Reactive Power, and Apparent
Power.
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
The consumption of real power is associated with circuit resistance.
Real Power
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
The primary characteristic of a resistor is that when a current and voltage are present, energy is
lost is the form of heat.
Real Power
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
Reactive Power
Reactive power is the power that is consumed by reactive elements within a circuit.
These elements are ideally inductors and capacitors.
Reactive power is expressed as VARS.
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
Reactive power can be thought of as the amount of power that is required to make magnetic
fields.
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
A distribution system, has both reactive and resistive components.
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
The resultant power produced by the station is called Apparent Power.
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
The Power Triangle
TB1-17
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
In AC circuits operating under steady state conditions, all of the currents and voltages vary at the same frequency; however the voltages and currents are normally out of
phase.
Aspects of AC Quantities
TB1-18
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
Phase Relationships
Lagging
Voltage leads Current
Found in Inductive Systems
TB1-21
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
Phase Relationships
Unity
Voltage and Current are in phase
Found in Purely Resistive Systems
TB1-21
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!
Phase Relationships
Leading
Current leads Voltage
Found in Capacitive Systems
TB1-21
GE Power Systems
Revision Date: 02/10/2000Revision Date: 02/10/2000 Property of Power Systems University- Proprietary Information for Training Purposes Only!Property of Power Systems University- Proprietary Information for Training Purposes Only!