Exciter Basics
Sep 09, 2014
Exciter Basics
DCExctr
DCExctr
SYNMach
AutomaticControl
MOT
PilotExciter
ForcingDown
ForcingUp
MainExciter
CTPTS
FixedResistor
QL QR
NL NR
ExciterField
Rheostat(ManualControl)
AC VoltageAdjuster
Notes: (1) NL, NR - Close for small errorQL, QR - Close for large error
DC Generator-Commutator Exciter Separately Excitedwith Noncontinuously Acting Rheostatic Regulator
DCExctr
SYNMach
CTPTS
AutomaticControl
AC VoltageAdjuster
PMG
RotatingAmplifier
RegulatorTransfer
Exciter FieldRheostat(Manual Control)
MOT Station Auxiliary Power
DC Generator-Commutator Exciter with Rotating Amplifier
AutomaticControl
DCExctr
SYNMach
CTPTS
RegulatorTransfer
Exciter FieldRheostat(Manual Control)
StationAuxiliaryPower
MOT AC VoltageAdjuster
PMG
DC Generator-Commutator Exciter with Continuously Acting Regulator Employing Static Amplifiers
StatorACExc GEN
RotorPMG
Perm.Mag.
Power Amp
Stator
ShuntDC
41
AC
+ -
DCIsolation
Transducer LimitingAnd
Protection
AC Reg.
FiringCircuit
Voltage Adjuster
ACIsolation
CT
PT
-+
Pulses
PMGAC
ExctrArm.
NS
PMSYNMach
ExciterField
CT
PTS
AutomaticControl
GateControl
RegulatorTransfer
AC VoltageAdjuster
BaseVoltageAdjuster(ManualControl)
Alternator-Rectifier Exciter Employing RotatingNoncontrolled Rectifiers (Brushless)
FeedbackInputs
Tur
bine
To Set UpTransformer
Generator
ControlledRectifier
ReferenceInputs
PermanentMagnet
Generator(PMG)
Exciter
Rotating Elements• Generator field• diode wheel with fuses• exciter armature• PMG field
ALTERNATOR EXCITERBrushless Type
SYNMach CT
PTS
GateControl
ManualControl
AutomaticControl
Start-UpPower
PowerPT
AC VoltageAdjuster
RegulatorTransfer
DC VoltageAdjuster
Potential Source-Rectifier Exciter Employing Controlled Rectifiers
GEN
AC IsolationTransducer
PT’s CT
120 VAC 4 VAC
TO DCADJ
REGTRIP
UNITTRIP
OXP
Damping
MEL
V/HZ
MXL
VED
AC Adj.
+/-10v
+/-10v
+/-10v
+/-10v
SIGMIX
+/-10v
BALMeter
DC Adj.
To AllModules
Auto
1pu=5v
Power AMP
15 VDCSupply
TransMOD
StartRES
Shunt
CurrentTransducer
WTA-300 STATIC
4:1 1pu=5v
DC Reg
Main
+/-10v
Firing Ckt
Power FromStation Service
Or Power FromPower PotentialTransformer41
To FiringCKT Phase
Back
VoltageTransducer
Feedback Control - Limiters
• Auto and Manual Operation
• Minimum Excitation Limiter
• Maximum Excitation Limiter OEL
• Volts/Hertz Limiter
• Overvoltage Limiter
• Instantaneous Current Limiter
Minimum Excitation Limiter• Generator Capability Curve -UEL
– Time Delay Curve and Gain– Adjustable 100%-130%– On Line-Off Line– Dynamic Pickup based on Pressure/Temperature
• Steady State Stability Limit - MEL– Varies Proportional -
• Square of Generator Terminal Voltage
Maximum Excitation Limiter OEL
• Limits Generator Field Current or Voltage• Adjustable Pickup Point
– On Line setting 100% -130%– Off Line setting 100% -200%
• Adjustable Time Delay • Dynamic Pickup based on Pressure/Temperature
Instantaneous Current Limiter
• Adjustable Pickup Point – 100%- 150% Field Current or– 100% - 300% Full Load Voltage
• Maintain Output – Within +/- 2% of Pickup Point
Volts/Hertz Limiter
• Adjustable Pickup Point 100%-120%• Adjustable Time Delays 0 - 1000 seconds• Inverse V/HZ Curve - ANSI C37.102
Overvoltage Limiter
• Limits Generator Voltage• Adjustable Pickup Points 100% - 130%• Adjustable Time Delay 0 - 10 sec.
Protection• Overexcitation Protection
• Volts/Hertz Protection
• Overvoltage Protection
• Minimum Excitation Protection
• Loss of Field Protection
• Loss of Sensing
Overexcitation Protection
• Configurable to Field Current or Field Voltage• On Line - Off Line Adjustable Settings• On Line - 100%-170% Full Load Value• Off Line 100% to 130% No Load Value• Dynamic Pickup based on Pressure/Temperature
Volts/Hertz Protection
• Adjustable Pickup Point 100% -120%• Adjustable Time Delay 0 - 1000 Seconds• Inverse Volts/Hertz Curve Per ANSI C37.102• Alarm On Pickup - Trip after Time Delay
Overvoltage Protection
• Adjustable Pickup 100-200% Generator voltage• Adjustable Time Delay• Alarm on Pickup• Trip After Time Delay
Minimum Excitation Protection
• Based upon Generator Capability Curve• Operating Curves approximated via:
– Five straight line segments
• Adjustable Time Delay on Trip• Dynamic Pickup based on Pressure/Temperature
Loss of Field Protection
• Based upon Steady State Stability Limit• Operating Curves approximated via:
– Five straight line segments
• Adjustable Time Delay on Trip• Varies Proportional
– Square of Generator Terminal Voltage
Loss of Sensing• Detects complete/partial Loss of Voltage Intelligence• Transfer based upon Adjustable Comparison• Comparison Configurable to:
– PT Secondary Voltage
• Configurable To Transfer to– Backup Metering PT’s (If existing)– Manual Control
GEN
AC IsolationTransducer
PT’s CT
120 VAC 4 VAC
TO DCADJ
REGTRIP
UNITTRIP
OXP
Damping
MEL
V/HZ
MXL
VED
AC Adj.
+/-10v
+/-10v
+/-10v
+/-10v
SIGMIX
+/-10v
BALMeter
DC Adj.
To AllModules
Auto
1pu=5v
Power AMP
15 VDCSupply
TransMOD
StartRES
Shunt
CurrentTransducer
WTA-300 STATIC
4:1 1pu=5v
DC Reg
Main
+/-10v
Firing Ckt
Power FromStation Service
Or Power FromPower PotentialTransformer41
To FiringCKT Phase
Back
VoltageTransducer
Two Basic Purposes of Firing Circuit1. To provide proper firing pulses at the right time to the thyristors
in power amplifier(s), such that –
2. The DC output from the power amplifier(s) is a Linear function of the DC control input to the firing circuit.
Power Amp.
Bridge
FieldDCOut
PowerACIn
+
-
FiringCircuit
DCControl
In
3Ph AC Timing (Same Ph. As AC Power)
Thyristor
Anode
GateCathode
+
-
I-
+
I
+
VGT
VDRM
- +-
VDRM
(Forward Blocking Voltage600 to 12KV.
IT(AV)
(Average Forward Current)100 to 5000 A.
VGT
(Gate Trigger Voltage)1 to 5 V.
IGT
(Gate Trigger Current)100 ma. To 500 ma.
1 2 1 2
Anode-Cathode Voltage
1
Thyristor Current in a resistive load
1 IAV.
2
IAV.
2
Thyristor Current in a resistive load
DC Output
AC Input
VDC
IDC
+
+
-
-
VDC
IDC
+
+
-
-DC Output
AC Input
One-Quadrant Converter
Two-Quadrant Converter
X1 Y1 Z1
X2 Y2 Z2
+R
L(>>R)
-
123
3-Phase6 PulseConverter
0o Delay
I
3-Phase6 PulseConverter
30o Delay
X1 Y1 Z1
X2 Y2 Z2
+R
L(>>R)
-
123 I
3-Phase6 PulseConverter
60o Delay
X1 Y1 Z1
X2 Y2 Z2
+R
L(>>R)
-
123 I
3-Phase6 PulseConverter
90o Delay
X1 Y1 Z1
X2 Y2 Z2
+R
L(>>R)
-
123 I
3-Phase6 PulseConverter
120o Delay(Transiently Only)
X1 Y1 Z1
X2 Y2 Z2
+R
L(>>R)
-
123 I
-1.0
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
Universal Relationship between the DC output terminal voltage and the firing angle, for all 2-quadrant phase-controlled converters (with smooth DC current).
D-C
Te
rmin
al V
olta
ge
in P
.U.
Firing Angle
0o
60o
180o
PowerAmp.
Firing Angle
DCOut
0o
60o
180o
DCIn
FiringCircuit
The key is to make the firing circuit like this
FiringDCIn
AmpDCOut
So thatRESULTSare this!!!