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Electrical Engineering
Electrical engineering is a field of engineering that deals with the study and application of electricity, electronics and electromagnetism.
23,056 Questions
What is the difference between shunt generators and series generators?
1. In Shunt generators armature current is equal to sum of field current and load current whereas in series generators field current and load current is same.
2. Shunt generators field winding has high resistance and large no of turns as compared to series generators.
3. Shunt generator field winding has thin conductor and series generator has thick.
How many amps are in 400 horsepower with 480 volt three phase?
This might help you. First and foremost is the information the manufacturer puts on the nameplate of the motor. Second, the generic amperage can be found on motor charts that are on the Internet. Third you can use a formula to find the approximate amperage. HP = Amps x Volts x 1.73 x %Eff x pf/746. Transposed for Amperage, Amps = HP x 746/Volts x 1.73 x %Eff x pf. Use power factor = .9. Eff = 746 x Output HP/Input watts use 1.5. For estimating a 400 HP motor running on 480 volts. Amps = 400 x 746/ 480 x 1.73 x 1.5 x .9 = 298400/747.36 = 399.27 amps. See how much easier it is to read the nameplate.
Can you use 24 volt transformer to powers 12v lights?
You can if you want to connect two 12 volt lights in series with each other. Make sure that the 12 volt lights are rated for AC and not DC.
CommentFurther to the above answer, you must also ensure that the two lamps have identical power ratings, or the lamp with the lower power rating will be brighter than the one with the higher power rating!
What is the instantaneous voltage at 180 degrees for peak voltage of 150 volts?
Zero. If voltage starts at zero at zero degrees, it rises to peak voltage at 90 degrees. Voltage then reaches zero at 180 degrees and heads for negative peak voltage at 270 degrees and then back to zero at 360 degrees.
What is the voltage of a pylon?
there are 3 main types of power pylons,400,000volts(400kv) usually there are 4 wires on each arm,275,000volts(275kv)usually 2wires,and 132,000volts(132kv)usually 1 wire.
CommentPylons, or to give them their correct name, 'towers', are used in electricity transmission systems and, to some extent, in distribution systems. Their operating voltages depend on the electricity standards in the country in which they are used. As pointed out in the original answer, in the UK, transmission voltages are 400 kV, 275 kV, and 132 kV; towers are also used, in some cases, to support distribution lines that operate at 66 kV and 33 kV (although these are more-commonly supported on poles).
In most cases, each tower supports two separate circuits -one on either side of the tower- with each circuit comprising three 'lines' (L1, L2, and L3)- often with one circuit having its line sequence reversed.
As the original answer indicates, at higher voltages, each 'line' consists of 'bundled' conductors (four per line at 400 kV, two per line at 275 kV). The purpose of bundling these conductors is to reduce the electric field stress that would otherwise exist at the surface of single conductors.
Why does under voltage cause overheating?
Overheating is a result of too much current flowing. AC motors are constant power devices, meaning they require the same amount of power to spin under a specific load. Power is equivalent to voltage times current. If voltage to a motor sags, the motor will attempt to make up the lack of voltage with an increase in current so the power stays the same. If voltage sags too much, the motor will overheat.
How do you calculate kvar of capacitor bank if you know only the kw?
Your question is rather vague. Are you asking how do you determine the reactive power of a capacitor bank necessary to improve the power factor of a load (in which case, is it a single-phase or a three-phase load), or are you asking how to convert a capacitor bank's capacitance into reactive power?
If the former, then you need to know the reactive power of the load before power factor-improvement, and the resulting reactive power after power-factor improvement, and the difference between these two will tell you how much reactive power you need to add in the form of capacitors.
Is BJT is a current control device or voltage control device?
transistor is a current controlled device. as the current flows through the base of the transistor , it works like a close switch.
What size resistor is needed to drop 24 volts dc to 12volts dc?
Its dependent what will by rated power of the device (current).
What is the density of transformer oil?
Density of Transformer Oil at 29.5oC is 0.89g/cm3.
The exact density of transformer oil depends upon the manufacturer but, expressed in SI units, is typically a little less than 900 kg/m3 at 20oC. The J&P Transformer Book states that 'a limit of 895 kg/m3 at 20oC ensures that the temperature (of the oil) must fall to -20oC before the density of the oil would exceed that of ice' -thus ensuring that if ice forms, then it would remain at the bottom of the tank.
How you increase current by keeping voltage constant?
If you are referring to a simple circuit, you could add resistance throughout it. Increased resistance means decreased current flow yet the same voltage.
What is the purpose of ballast in lighting?
The ballast is a transformer that steps the voltage up higher than its incoming voltage.
This is usually used with flourescent, metal halide, & sodium vapor lights.
The higher voltage is needed to 'excite' the gases within the bulbs and make the molecules bounce around and give off light.
Difference between 2 core wire and 4 core wire?
in 4 core cable all four cables are equal dia and in a 3.5 core cable 3 cores are equal dia and fourth one will be with half dia. and it is used for neutral in 3phase 4 wire syastem
Wire size for 500 feet distance 120 volt 20 amps?
The American Wire Gauge code table shows 8 gauge safe for 24 Amps, 10 Gauge for 15 Amps. If the circuit is going to be used at capacity (2400 Watts in this case), 8 or 10 gauge is the minimum, if load is constant, use 8 gauge.
Voltage ability of the wire is dependent on the insulation thickness and material. So 20 amps at 120 Volts is 2400 watts of power, and 20 amps at 12 volts is 48 watts of power. Both would require the same gauge of wire, but the higher voltage would need better insulation.
<<>>
This is a voltage drop question.
A #1 copper conductor will limit the voltage drop to 3% or less when supplying 20 amps for 500 feet on a 120 volt system.
What do the colors on a resistor mean?
Most resistors have either 3 or 4 color bands. The fourth, if it is there, only indicates the tolerance, or how accurate the value is. For the first three bands, the following colors may be used: black = 0 or X1 brown = 1 or X10 red = 2 or X100 orange = 3 or X1000 yellow = 4 or X10000 green = 5 or X100000 blue = 6 or X1000000 violet = 7 gray = 8 white = 9 A resistor uses the first two color bands to form a 2 digit number, then a third band to add a multiplier. For instance, suppose you have a resistor that has a red, violet, brown color code. Decoding: red = 2 violet = 7 27 brown = X10 27 * 10 = 270 In this case, you are holding a 270 ohm resistor. How about a 2.2K resistor? Well, K = 1000, so 2.2K is the same as 2200 ohms. Reverse decoding: The first two bands would have to be red, red (22). To get to 2200 from 22 we have to multiply by 100, so the third band would also be red (X100). The last, or fourth band indicates how close to the nominal value the resistor is. The band colors are: none = 20% silver = 10% gold = 5% So, if the 2.2K resistor is red, red, red, silver, it means the actual resistance can be as much as 10% (or 220 ohms) higher or lower than 2.2K, or anywhere from 1980 ohms to 2420 ohms. You can get resistors with better accuracy than 5%, such as 2%, 1%, 0.1%. Some use three number bands and a fourth multiplier band, others have no bands at all, just the actual resistance printed as a number on the body. If in doubt, measure the resistor with an ohmmeter to be sure.
What happens when a the electrical voltage is low?
Appliances at home have designated voltage e.g. 220 V or 110 V. When the voltage is dropped, the appliances try to run at their designated power in kW as usual. To keep the power same, current is increased (P = VI). This increase in current can burn the most delicate part of the appliances if the low voltage is experienced persistently.
AnswerA drop in supply voltage results in a drop in the power of appliances. For fixed-resistance devices, a 10% drop in voltage results in approx, 18% drop in power.
What are the 4 parts of a technological system?
The for parts of the computer system are
1,hardware
2,software
3,data
4,users
What are the application of chemistry in civil engineering?
Actually its answer is very easy and very simple where as you know that all things made by soem chemistry formula where you know that a metal is combinations of amny metals and also some chemicals which are used in different technology also made by combinations of different chemicals so the role of chemistry is much more important in each and every technology even in civil technology,,,, i think there will be no more capacity to understand you about it,,,
How governing system of steam turbine is being done?
(pictures insert is not being allowed by wiki. i am sorry)
TOPICS OF DISCUSSION
CONCEPT OF GOVERNING SYSTEM
FEATURES OF KWU GOVERNING SYSTEM
OVERVIEW OF GOVERNING RACK
FUNCTIONING OF EHC CIRCUITS
FREE GOVERNOR MODE OPERATION
BEST PRACTICES IN GOVERNING SYSTEM
EMERGENCIES IN GOVERNING SYSTEM
WHAT IS GOVERNING SYSTEM ?
n Turbine Governing system is meant for regulation of turbine speed under no load and varying load condition.
n It helps in precise control of grid frequency under normal operation and protects the machine as well as grid during emergency situation.
KWU GOVERNING SYSTEM-FEATURES
n ELECTRO-HYDRAULIC GOVERNING SYSTEM WITH HYDRAULIC BACKUP
n OPERATION OF STOP VALVES BY STARTING & LOAD LIMITING DEVICE (HYDRAULIC)
n ROLLING, SYNCHRONIZATION & LOAD OPERATION BY HYDRAULIC / ELECTRO- HYDRAULIC SYSTEM
n ELECTRO- HYDRAULIC SPEED GOVERNOR WITH HYDRAULIC BACK UP
n SAFE SHUTDOWN BY HYDRAULIC / ELECTRO- HYDRAULIC SYSTEM
n ELECTRICAL AND HYDRAULIC PROTECTION SYSTEM ALONG WITH TEST FACILITIES
FEATURES OF EHC
n AUTO ROLLING & SYNCHRONIZATION THROUGH SPEED CONTROLLER UNDER INFLUENCE OF TSE
n CONSTANT LOAD OPERATION BY LOAD CONTR. WITH PRESSURE CONTR. AS BACKUP
n RUNBACK OPERATION THROUGH PRESSURE CONTR.
n EMERGENCY OPERATION THROUGH SPEED CONTR.
n AUTO GRID FREQUENCY CONTROL THROUGH EXTERNAL FREQUENCY INFLUENCE
n AUTO UNLOADING AT HIGH FREQUENCY THROUGH INTERNAL FREQUENCY INFLUENCE
n CONTROL DURING AUTOMATIC TURBINE TESTING,
ISOLATED GRID CONDITION & LSR OPERATION
SPEED CONTROLLER CIRCUIT
L - Raise & Lower command from UCB :
nr - Speed Reference :
nr limit - Delayed Speed Reference :
NLC - No Load Correction (Ensures required Speed controller O/P for Rolling even when Speed reference n r matches n act.)
n act - Actual Speed :
hr nc - Speed Controller O/P with DROOP of + / - 10.0 V for nr lim ~ n act = 150 RPM ( GAIN = 22
LOAD SET POINT GENERATION CIRCUIT
1 - SET POINT FOLLOW UP when Automatic Grid Control or CMC In service
(Other Raise / Lower commands get blocked)
2 -- TSE ENABLING when
A) GCB is closed AND
B) Load controller (L C) not OFF AND
C) Fast calibration signal 6 absent AND
D) I) Load controller (L C) in control
OR ii) Pressure controller with initial pressure in action
OR iii) Turbine follow mode in service
This helps to bring manually adjusted gradient and stress effect in service.
+/- 10 V gradient => +/- 25 MW / MIN for 200 MW units
OR +/- 50 MW / MIN for 500 MW units.
PRESSURE CONTROLLER CIRCUIT
EHC TRANSFER CIRCUIT
FGMO - BACKGROUND
n Unique frequency band of 49.0 Hz to 50.5 Hz, as specified by IEGC
n Scheduling & dispatch by RLDCs/SLDCs is based on day ahead demand & availability
n Frequency control by load-generation balance in every 15 mins time block
n Wide frequency variation during Grid disturbance, Unit outage, change in demand, etc.
n No primary response by generators to maintain frequency under such system contingency
n Emergencies caused due to frequency control only through importing /cutting load by system operator
n
FGMO - GRID CODES
n All generating units should have their speed governors in normal operation at all times to enable Grid frequency control by loading / unloading
n Droop characteristic for primary response should be within 3% to 6%
n Each unit shall be capable of instantaneously picking up at least 5% extra load for a minimum of 5 mins (up to 105%MCR), during fall in frequency
n No dead bands and/or time delays shall be deliberately introduced
n Facilities like load limiters, CMC, etc. shall not be used to suppress the normal governor action
IMPLEMENTATION OF FGMO
In line with clause Clause 1.6 of IEGC and CERC order dated 30-10-99, date of FGMO implementation, as decided by REBs are :-
n Western Region - 19-05-03 ( ABT - 01-07-02 )
n Southern Region - 01-08-03 ( ABT - 01-01-03 )
n Northern Region - 01-10-03 ( ABT - 01-12-02 )
n Nor-East Region - 22-12-03 ( ABT - 01-11-03 )
n Eastern Region - 02-01-04 ( ABT - 01-04-03 )
FGMO CHARACTERISTIC FOR KWU M/C
MAJOR ISSUES WITH FGMO IN 2004
Ø Wide and frequent variation of freq.
Ø Perpetual oscillations in critical parameters due to Boiler response time
Ø M/C subjected to cyclic loading and fatigue stresses
Ø Frequent HP/LP Bypass valve operation
Ø Continuous manual interventions
Ø Self-defeating feature(Unloading when freq. improving towards 50 Hz)
Ø Conflict with ABT(Offsetting freq. correction)
TRANSIENTS IN GOVERNING SYSTEM
n FAILURE OF POWER PACKS OF CONTROLLER RACKS IN EHC PANEL
n POWER SUPPLY FAILURE IN ATRS PANEL
n SIGNAL ACQUISITION PROBLEM
n FAILURE IN TURBINE SYSTEM
n ELECTRICAL SYSTEM FAILURE
n COMPONENT FAILURE IN GOVERNING RACK
n OPERATIONAL EMERGENCY
1 CONTROL RACK SUPPLY FAILURE
n M/C is on EHC. Power supply fails in Load control/Pressure control / transfer circuit rack. Starting device becomes off automatically due to EHC fault.
Observation: EHC output is minimum/zero and load minimum/ zero with EHC fault alarm. Machine on bar with ESV & IV open (Turbine not tripped).
Action: Confirm HP/LP bypass opening, isolate EHC from governing rack and parallely adjust starting device position from UCB. Reduce boiler firing to restrict rise in boiler pressure.
2) SUPPLY FAILURE IN ATRS PANEL(ATRS=Automatic Turbine Rolling & Synchronisation)
n M/C is on EHC. Power supply fails in CCA panels only.
Observation: All indication lamps in ATRS consoles will go off. EHC output and Load will become zero due loss of GCB close feedback. All ATRS drives will become inoperative.
Action: Confirm HP/LP bypass opening , isolate EHC. Reduce boiler firing. Adjust starting device position from local. Normalize power supply in CCA panels at the earliest.
3) SIGNAL ACQUISITION PROBLEM
n Loss of speed signal occurs due to Hall Probe / card failure.
Observation: Speed indication will become zero. M/C will be loaded through speed controller. Subsequently Pressure controller will come in service. AOP & JOP will take auto start & Barring Gear valve Will open on auto.
Action: Isolate EHC and adjust Starting device position. If pressure oil pressure is normal, make SLC of AOP, JOP and Barring Gear vlv OFF and stop AOP, JOP and close Barring Gear vlv.
4)FAILURE IN TURBINE SYSTEM
n Loss of speed signal occurs due to breakage of MOP shaft.
Observation: Speed indication and pressure oil pressure will come down. M/C will be loaded through speed controller and Pressure controller will come in service. Subsequently, AOP & JOP will take auto start &Barring Gear valve. will open on auto.
Action: Safe shutdown of M/C is to be ensured.
5) ELECTRICAL SYSTEM FAILURE
n M/C is on EHC with Tracking on. Starting device becomes inoperative due to Electrical module trouble/motor failure/overload.
Observation: During increase in boiler firing, Boiler pressure will increase due to load restriction by Starting device. EHC output will go to 100%.
Action: Switch off the electrical module of Starting device and increase Starting device position from local so that EHC can take control.
6) FAILURE IN GOVRRNING RACK
n EHC Plunger coil failure
n EHC Pilot valve bearing failure
Observation: EHC starts hunting
Action: Isolate EHC and take Hydraulic mode in service. Replace the failed omponent. Governing characteristic checking should be done before EHC is put in service
n Speeder Gear spring tension gets altered.
Observation: M/C may get unloaded at frequency lower than recommended value.
Action: Speeder Gear spring tension may be adjusted to increase the start of unloading.Testing for proper setting should be checked during suitable opportunity.
LOGICS
A SPEED CONTROLLER LOGICS
1 Command for slow rate at nr > 2850 RPM to facilitate easy synchronisation
2 TSE Influence ON, when min of all the upper stress margins comes into picture to control gradient of nr lim and hence, acceleration of Rolling speed. Upper stress margin = 30 deg C => 10.0 V => 600 RPM ~ (Acceleration < 108 RPM ~ causes dn / dt tripping)
B LOAD SET POINT GENERATION LOGICS
1 Stopping of nr lim when
a) GCB open AND
b) n act is < nr lim by approx. 45 RPM.
This restricts hr nc up to around 30 % during Rolling to avoid wide v/v opening.
2 Stopping speed set point control when,
a) n act > 2850 RPM AND
b) nr raised ( I.e, nr > nr lim) AND
c) I) TSE ON and faulted in GCB open condition
OR ii) Stop command from SGC in SGC ON condition.
3 Tracking in synchronized condition if
a) Frequency within limit (adjustable, say 48.5 to 51.5 Hz.) AND
b) Load controller O/P , hr PC > hr nc AND
c) I) Load controller (L C) in control
OR ii)Pressure controller in action
4 Set Point Follow Up (Fast Calibration) during
a) Tracking condition 5 ( nr = n act + 21 RPM ) OR
b) Turbine Trip ( nr = n act - 120 RPM ). Simultaneously nr lim immediately equals to nr
Condition (a) ensures certain speed controller O/P during emergency to keep machine in rolled condition along with some load.
Condition (b) ensures negative speed controller O/P during Trip condition.
LOAD CONTROLLER (L C) IN CONTROL CONDITIONS -
a) Speed OR Pressure Controller not in action AND
b) Isolated Grid condition absent AND
c) Both Load Controller OFF and Schedule OFF absent (I.e, L C ON)
LOAD CONTROLLER SCHEDULE OFF - L C can be made OFF if Speed controller is in action and hrnc > hr PC. Otherwise, with OFF command OFF lamp blinks - called Schedule OFF
C .LOAD SET POINT GENERATION LOGICS
1TSE ON AND NOT FAULTED
This helps to keep stress effect for gradient control in service.
2-- LOAD GRADIENT ON
This helps to keep manual gradient control in service
3-- STOP POWER SET POINT CONTROL when
a) TSE ON and Faulted OR
b) Stop command from SGC OR
c) Pr raised when Pressure controller is in action with CMC ON OR Limit pressure mode selected OR Boiler follow mode selected
In above conditions Pr lim stops, I.e,Set point can not be increased.
4-- FAST CALIBRATION when
a) Pressure controller is in action OR
b) Follow above (h v0) condition present
Under this condition MW error (ep) is selected and Pr lim immediately equals to Actual load (P act) without any gradient .
5 -- FREQUENCY INFLUENCE ON
This is made ON from ATRS panel to put EXTERNAL FREQUENCY EFFECT in service for
loading / unloading w.r.t. 50 Hz ( with 2.5 % to 8 % Frequency Droop)
6 TSE TEST RELEASE : TSE TEST (For checking healthiness of TSE Margins) can be done when
a) TSE Influence is OFF OR
b) Both Pr, Pr lim and hr, hr lim are balanced, I.e, Speed and Power set point controls are not in action.
D .LOAD CONTROLLER LOGICS
FOLLOW ABOVE ( h v0 ) --
a) GCB closed and load < 10 % (station load) OR
b) GCB open OR
c) Load controller OFF
Absence of these conditions help Load controller output to track above Pressure controller output when Pressure controller is in service.
FOLLOW LOW ( h vu ) - GCB CLOSED AND Speed controller in action.
This helps Load controller output to track below Speed controller output.
8 -- Either a) Initial pressure mode selected OR
b) Turbine follow mode in action OR
c) CMC Runback active
This ensures Load controller output above pressure controller output
9 -- Load controller OFF
This defeats transmission of Load Controller output to Transfer circuit.
R & L - Raise & Lower command from UCB :
nr - Speed Reference :
nr limit - Delayed Speed Reference :
NLC - No Load Correction (Ensures required Speed controller O/P for Rolling even when Speed reference n r matches n act.)
n act - Actual Speed :
hr nc - Speed Controller O/P with DROOP of + / - 10.0 V for nr lim ~ n act = 150 RPM ( GAIN = 22
LOAD SET POINT GENERATION CIRCUIT
1 - SET POINT FOLLOW UP when Automatic Grid Control or CMC In service
(Other Raise / Lower commands get blocked)
2 -- TSE ENABLING when
A) GCB is closed AND
B) Load controller (L C) not OFF AND
C) Fast calibration signal 6 absent AND
D) I) Load controller (L C) in control
OR ii) Pressure controller with initial pressure in action
OR iii) Turbine follow mode in service
This helps to bring manually adjusted gradient and stress effect in service.
+/- 10 V gradient => +/- 25 MW / MIN for 200 MW units
OR +/- 50 MW / MIN for 500 MW units.
PRESSURE CONTROLLER CIRCUIT
EHC TRANSFER CIRCUIT
FGMO - BACKGROUND
n Unique frequency band of 49.0 Hz to 50.5 Hz, as specified by IEGC
n Scheduling & dispatch by RLDCs/SLDCs is based on day ahead demand & availability
n Frequency control by load-generation balance in every 15 mins time block
n Wide frequency variation during Grid disturbance, Unit outage, change in demand, etc.
n No primary response by generators to maintain frequency under such system contingency
n Emergencies caused due to frequency control only through importing /cutting load by system operator
n
FGMO - GRID CODES
n All generating units should have their speed governors in normal operation at all times to enable Grid frequency control by loading / unloading
n Droop characteristic for primary response should be within 3% to 6%
n Each unit shall be capable of instantaneously picking up at least 5% extra load for a minimum of 5 mins (up to 105%MCR), during fall in frequency
n No dead bands and/or time delays shall be deliberately introduced
n Facilities like load limiters, CMC, etc. shall not be used to suppress the normal governor action
IMPLEMENTATION OF FGMO
In line with clause Clause 1.6 of IEGC and CERC order dated 30-10-99, date of FGMO implementation, as decided by REBs are :-
n Western Region - 19-05-03 ( ABT - 01-07-02 )
n Southern Region - 01-08-03 ( ABT - 01-01-03 )
n Northern Region - 01-10-03 ( ABT - 01-12-02 )
n Nor-East Region - 22-12-03 ( ABT - 01-11-03 )
n Eastern Region - 02-01-04 ( ABT - 01-04-03 )
FGMO CHARACTERISTIC FOR KWU M/C
MAJOR ISSUES WITH FGMO IN 2004
Ø Wide and frequent variation of freq.
Ø Perpetual oscillations in critical parameters due to Boiler response time
Ø M/C subjected to cyclic loading and fatigue stresses
Ø Frequent HP/LP Bypass valve operation
Ø Continuous manual interventions
Ø Self-defeating feature(Unloading when freq. improving towards 50 Hz)
Ø Conflict with ABT(Offsetting freq. correction)
TRANSIENTS IN GOVERNING SYSTEM
n FAILURE OF POWER PACKS OF CONTROLLER RACKS IN EHC PANEL
n POWER SUPPLY FAILURE IN ATRS PANEL
n SIGNAL ACQUISITION PROBLEM
n FAILURE IN TURBINE SYSTEM
n ELECTRICAL SYSTEM FAILURE
n COMPONENT FAILURE IN GOVERNING RACK
n OPERATIONAL EMERGENCY
1 CONTROL RACK SUPPLY FAILURE
n M/C is on EHC. Power supply fails in Load control/Pressure control / transfer circuit rack. Starting device becomes off automatically due to EHC fault.
Observation: EHC output is minimum/zero and load minimum/ zero with EHC fault alarm. Machine on bar with ESV & IV open (Turbine not tripped).
Action: Confirm HP/LP bypass opening, isolate EHC from governing rack and parallely adjust starting device position from UCB. Reduce boiler firing to restrict rise in boiler pressure.
2) SUPPLY FAILURE IN ATRS PANEL(ATRS=Automatic Turbine Rolling & Synchronisation)
n M/C is on EHC. Power supply fails in CCA panels only.
Observation: All indication lamps in ATRS consoles will go off. EHC output and Load will become zero due loss of GCB close feedback. All ATRS drives will become inoperative.
Action: Confirm HP/LP bypass opening , isolate EHC. Reduce boiler firing. Adjust starting device position from local. Normalize power supply in CCA panels at the earliest.
3) SIGNAL ACQUISITION PROBLEM
n Loss of speed signal occurs due to Hall Probe / card failure.
Observation: Speed indication will become zero. M/C will be loaded through speed controller. Subsequently Pressure controller will come in service. AOP & JOP will take auto start & Barring Gear valve Will open on auto.
Action: Isolate EHC and adjust Starting device position. If pressure oil pressure is normal, make SLC of AOP, JOP and Barring Gear vlv OFF and stop AOP, JOP and close Barring Gear vlv.
4)FAILURE IN TURBINE SYSTEM
n Loss of speed signal occurs due to breakage of MOP shaft.
Observation: Speed indication and pressure oil pressure will come down. M/C will be loaded through speed controller and Pressure controller will come in service. Subsequently, AOP & JOP will take auto start &Barring Gear valve. will open on auto.
Action: Safe shutdown of M/C is to be ensured.
5) ELECTRICAL SYSTEM FAILURE
n M/C is on EHC with Tracking on. Starting device becomes inoperative due to Electrical module trouble/motor failure/overload.
Observation: During increase in boiler firing, Boiler pressure will increase due to load restriction by Starting device. EHC output will go to 100%.
Action: Switch off the electrical module of Starting device and increase Starting device position from local so that EHC can take control.
6) FAILURE IN GOVRRNING RACK
n EHC Plunger coil failure
n EHC Pilot valve bearing failure
Observation: EHC starts hunting
Action: Isolate EHC and take Hydraulic mode in service. Replace the failed omponent. Governing characteristic checking should be done before EHC is put in service
n Speeder Gear spring tension gets altered.
Observation: M/C may get unloaded at frequency lower than recommended value.
Action: Speeder Gear spring tension may be adjusted to increase the start of unloading.Testing for proper setting should be checked during suitable opportunity.
LOGICS
A SPEED CONTROLLER LOGICS
1 Command for slow rate at nr > 2850 RPM to facilitate easy synchronisation
2 TSE Influence ON, when min of all the upper stress margins comes into picture to control gradient of nr lim and hence, acceleration of Rolling speed. Upper stress margin = 30 deg C => 10.0 V => 600 RPM ~ (Acceleration < 108 RPM ~ causes dn / dt tripping)
B LOAD SET POINT GENERATION LOGICS
1 Stopping of nr lim when
a) GCB open AND
b) n act is < nr lim by approx. 45 RPM.
This restricts hr nc up to around 30 % during Rolling to avoid wide v/v opening.
2 Stopping speed set point control when,
a) n act > 2850 RPM AND
b) nr raised ( I.e, nr > nr lim) AND
c) I) TSE ON and faulted in GCB open condition
OR ii) Stop command from SGC in SGC ON condition.
3 Tracking in synchronized condition if
a) Frequency within limit (adjustable, say 48.5 to 51.5 Hz.) AND
b) Load controller O/P , hr PC > hr nc AND
c) I) Load controller (L C) in control
OR ii)Pressure controller in action
4 Set Point Follow Up (Fast Calibration) during
a) Tracking condition 5 ( nr = n act + 21 RPM ) OR
b) Turbine Trip ( nr = n act - 120 RPM ). Simultaneously nr lim immediately equals to nr
Condition (a) ensures certain speed controller O/P during emergency to keep machine in rolled condition along with some load.
Condition (b) ensures negative speed controller O/P during Trip condition.
LOAD CONTROLLER (L C) IN CONTROL CONDITIONS -
a) Speed OR Pressure Controller not in action AND
b) Isolated Grid condition absent AND
c) Both Load Controller OFF and Schedule OFF absent (I.e, L C ON)
LOAD CONTROLLER SCHEDULE OFF - L C can be made OFF if Speed controller is in action and hrnc > hr PC. Otherwise, with OFF command OFF lamp blinks - called Schedule OFF
C .LOAD SET POINT GENERATION LOGICS
1TSE ON AND NOT FAULTED
This helps to keep stress effect for gradient control in service.
2-- LOAD GRADIENT ON
This helps to keep manual gradient control in service
3-- STOP POWER SET POINT CONTROL when
a) TSE ON and Faulted OR
b) Stop command from SGC OR
c) Pr raised when Pressure controller is in action with CMC ON OR Limit pressure mode selected OR Boiler follow mode selected
In above conditions Pr lim stops, I.e,Set point can not be increased.
4-- FAST CALIBRATION when
a) Pressure controller is in action OR
b) Follow above (h v0) condition present
Under this condition MW error (ep) is selected and Pr lim immediately equals to Actual load (P act) without any gradient .
5 -- FREQUENCY INFLUENCE ON
This is made ON from ATRS panel to put EXTERNAL FREQUENCY EFFECT in service for
loading / unloading w.r.t. 50 Hz ( with 2.5 % to 8 % Frequency Droop)
6 TSE TEST RELEASE : TSE TEST (For checking healthiness of TSE Margins) can be done when
a) TSE Influence is OFF OR
b) Both Pr, Pr lim and hr, hr lim are balanced, I.e, Speed and Power set point controls are not in action.
D .LOAD CONTROLLER LOGICS
FOLLOW ABOVE ( h v0 ) --
a) GCB closed and load < 10 % (station load) OR
b) GCB open OR
c) Load controller OFF
Absence of these conditions help Load controller output to track above Pressure controller output when Pressure controller is in service.
FOLLOW LOW ( h vu ) - GCB CLOSED AND Speed controller in action.
This helps Load controller output to track below Speed controller output.
8 -- Either a) Initial pressure mode selected OR
b) Turbine follow mode in action OR
c) CMC Runback active
This ensures Load controller output above pressure controller output
9 -- Load controller OFF
This defeats transmission of Load Controller output to Transfer circuit.
What is the difference between a secondary and primary coil?
The primary coil is the one with voltage applied, or the 'input'.
The secondary coil is the one in which a voltage is induced by electromagnetism, or the 'output'.
In a step up transformer, the secondary coil voltage is higher than the primary.
In a step down transformer, the secondary coil voltage is lower than the primary.
In an isolation transformer, the secondary coil voltage is the same as the primary. Here, the point of the transformer isn't to raise or lower voltage, but to keep a particular circuit electrically disconnected from another circuit, while still allowing the circuits to function together (through electromagnetism).
Why capacitor connected in parallel in circuit?
Any answer "why" will depend on the rest of the circuit, which may an electric motor, a filter, or any number of other applications.
If you're asking about 2 or capacitors in parallel, it is to provide a higher capacitance, since the total C will be the sum of each device's individual capacitances.
Ctotal = C1 + C2 + C3 ...+ Cn
Conversely capacitors in series obey the reciprocal law:
1/Ctotal = 1/C1 + 1/C2 + 1/C3 ...+ 1/Cn
Causes of hysteresis loss in transformer?
No, you're hysteresis losses are set by Bmax, frequency, and material. The function is highly nonlinear and the loss goes up disproportionately with Bmax.
When designing power transformers, you typically want the hysteresis + eddy losses to equal the copper losses.
A capacitor is used to store charge. It does this by the means of an electrochemical reaction. After the charging circuit is turned off, this charge - if not discharged by any means - is still present in the capacitor. High-Voltage capacitors can amass sufficient current for it to be lethal at said voltage, and they can deliver all of it at the slightest contact.
For example, a flasher circuit used in a typical photo camera can deliver lethal voltage, even when it's been charged from a 1.5V battery. The current doesn't need to be high (and is typically very low).
I've made this mistake more than once in my life, and I've had screwdrivers welded to the capacitor terminals by their charge. :D
It is worthy of note that some devices and circuits act as capacitors even when they're not designated as such! For example, a Cathode-Ray Tube (the big-ass thing in a tube TV) is a very good high-voltage capacitor itself, and can hold a charge for a long time (even weeks)!
Let C1=0.05F
& C2=0.025F, C1 & C2 are in series
Let the equivalent capacitance will be C
than 1/C = 1/C1 + 1/C2
1/C = 1/0.05 + 1/0.025 = 20 + 40 = 60F
hence C= 1/60 = 0.0166667 F
