K
Knobhead
I’ve asked Lenny to set up a new sticky thread for motors and their control. I hope others will help with diagrams and theories for the benefit of others.
Currently reading:
Motors
Discuss Motors in the Electricians' Talk | All Countries area at ElectriciansForums.net
OP
Knobhead
It’s going to take some time to put together. I want to start with basic motors and control but then going in to some more complex motors and starters.
I’ll apologise for the control drawings, they will be line drawings, not little blocks showing wire A in to terminal B. your going to have to use some thought to transpose them to your application.
The motors and starters I want to cover are:
AC:
Squirrel cage
Wound rotor
Dual speed
Dahlander (dual speed)
Schrage (the motor in my avatar) (variable speed)
DC:
Series
Shunt
Compound
Starters:
DOL
Star Delta (open transition)
Star Delta (closed transition)
Auto transformer (open transition)
Auto transformer (closed transition Korndorfer)
It’s not going to be a definitive guide, but based purely on experience so at times you may have to bear with me.
Other members of the board will give better information on modern soft start and VFD’s than I can.
I’ll apologise for the control drawings, they will be line drawings, not little blocks showing wire A in to terminal B. your going to have to use some thought to transpose them to your application.
The motors and starters I want to cover are:
AC:
Squirrel cage
Wound rotor
Dual speed
Dahlander (dual speed)
Schrage (the motor in my avatar) (variable speed)
DC:
Series
Shunt
Compound
Starters:
DOL
Star Delta (open transition)
Star Delta (closed transition)
Auto transformer (open transition)
Auto transformer (closed transition Korndorfer)
It’s not going to be a definitive guide, but based purely on experience so at times you may have to bear with me.
Other members of the board will give better information on modern soft start and VFD’s than I can.
Last edited by a moderator:
OP
Silly Sausage
Courtesy of The silva.foxx, there's a very good link in here...
http://www.electriciansforums.net/e...stop-start-contactor-overload.html#post381564
http://www.electriciansforums.net/e...stop-start-contactor-overload.html#post381564
OP
gerard
Hi,
See attached file on various motors - DC, AC, Universal, etc. and their characteristics. It's not perfect (the spelling!) but it will help if trying to choose a motor. Hope this helps.
Regards,View attachment 8737
See attached file on various motors - DC, AC, Universal, etc. and their characteristics. It's not perfect (the spelling!) but it will help if trying to choose a motor. Hope this helps.
Regards,View attachment 8737
OP
Knobhead
Motor windings
For R, Y, B read Brn, Blk, Gry I’ve not gone decimal yet, plus it’s quicker to type.
The most basic motors will have just three terminals in the TB. How it’s connected internally isn’t an option. The plate rating will state one voltage so other than rotation there’s not a lot to worry about. These are for direct on line starting only.
View attachment 8907View attachment 8908
Regarding rotation the convention is connect R, Y, B to A, B, C the rotation will be clockwise looking at the shaft. (Works 99% of the time).
Most motors will have six terminals A1 B1 C1 top row C2 A2 B2 bottom row. 1 being the start of the winding, 2 the end.
View attachment 8906
Some will be dual voltage others suitable for star/delta starting.
Dual voltage will have two options, typical will be 230V delta 400V star. Some you may come across are:
400/230
415/240
433/250
690/400
750/433
(I’ve only ever come across the higher voltage ones a couple of time in 35 years).
Motors suitable for star/delta starting will usually just give one voltage for delta. If the supply is up to it they will start direct on line.
View attachment 8904View attachment 8905
For R, Y, B read Brn, Blk, Gry I’ve not gone decimal yet, plus it’s quicker to type.
The most basic motors will have just three terminals in the TB. How it’s connected internally isn’t an option. The plate rating will state one voltage so other than rotation there’s not a lot to worry about. These are for direct on line starting only.
View attachment 8907View attachment 8908
Regarding rotation the convention is connect R, Y, B to A, B, C the rotation will be clockwise looking at the shaft. (Works 99% of the time).
Most motors will have six terminals A1 B1 C1 top row C2 A2 B2 bottom row. 1 being the start of the winding, 2 the end.
View attachment 8906
Some will be dual voltage others suitable for star/delta starting.
Dual voltage will have two options, typical will be 230V delta 400V star. Some you may come across are:
400/230
415/240
433/250
690/400
750/433
(I’ve only ever come across the higher voltage ones a couple of time in 35 years).
Motors suitable for star/delta starting will usually just give one voltage for delta. If the supply is up to it they will start direct on line.
View attachment 8904View attachment 8905
OP
Knobhead
OK I know this is in electrical thories but I wanted to put it in “motors”
Squirrel Cage Motors.
On starting the rotor is stationary so it draws what is called locked rotor” current. This can be 5 to 8 times the FLC. The current is regulated primarily by the resistance of the winding with a small inductive element. As speed increases the inductance increases while the resistive element remains the same.
Running light the motor turns at near it’s synchronous speed causing high inductance in the stator windings and therefore low current. The motor cannot achieve full synchronous speed, as a small amount of “slip” is needed to induce current in to the rotor’s squirrel cage. As load on the shaft is increased slip increases inducing more current in to the squirrel cage, which in turn reduces the inductance of the rotor allowing more current to flow through the windings.
Synchronous speeds for an induction motor is governed by the number of poles in the rotor. This is give by Hz X 60 / No. of poles. So at 50Hz the synchronous speed for a 2 pole motor it will be 3000RPM.
Squirrel Cage Motors.
On starting the rotor is stationary so it draws what is called locked rotor” current. This can be 5 to 8 times the FLC. The current is regulated primarily by the resistance of the winding with a small inductive element. As speed increases the inductance increases while the resistive element remains the same.
Running light the motor turns at near it’s synchronous speed causing high inductance in the stator windings and therefore low current. The motor cannot achieve full synchronous speed, as a small amount of “slip” is needed to induce current in to the rotor’s squirrel cage. As load on the shaft is increased slip increases inducing more current in to the squirrel cage, which in turn reduces the inductance of the rotor allowing more current to flow through the windings.
Synchronous speeds for an induction motor is governed by the number of poles in the rotor. This is give by Hz X 60 / No. of poles. So at 50Hz the synchronous speed for a 2 pole motor it will be 3000RPM.
OP
Knobhead
Re: Autotransformer starters
View attachment 9101
There are two types of autotransformer starters and to add to the confusion they are wired the same. The sequence and the transformer construction are different.
The standard starter is open transition where at the change over from start to run there is a brief moment when no power is supplied to the motor. This can cause mechanical stress to the motor and load.
The Korndorfer starter is closed transition, so no loss of power at change over. Because of this the transformer has to be a bit more “beefy”. But because there is no break in the supply to the motor there is no mechanical stress.
Standard starter, open transition:
contactors 1 and 3 close. Giving a reduced voltage to the motor
time delay
contactors 1 and 3 open
small time delay (no power to motor)
contactor 2 closes. Giving full power to the motor
Korndorfer starter, closed transition:
contactor 3 closes
small time delay
contactor 3 closes. Giving a reduced voltage to the motor
time delay
contactor 3 opens. The transformer is now acting as a choke
small time delay
contactor 2 closes. The transformer is now shorted between it’s incoming and % tappings. But as it's the same potential bewteen the two points there is no current flow
small time delay
contactor 1 opens.
As can you see the sequence for the Korndorfer puts stress on the transformer where it has to withstand acting as a choke. So for small motors it’s uneconomical.
View attachment 9101
There are two types of autotransformer starters and to add to the confusion they are wired the same. The sequence and the transformer construction are different.
The standard starter is open transition where at the change over from start to run there is a brief moment when no power is supplied to the motor. This can cause mechanical stress to the motor and load.
The Korndorfer starter is closed transition, so no loss of power at change over. Because of this the transformer has to be a bit more “beefy”. But because there is no break in the supply to the motor there is no mechanical stress.
Standard starter, open transition:
contactors 1 and 3 close. Giving a reduced voltage to the motor
time delay
contactors 1 and 3 open
small time delay (no power to motor)
contactor 2 closes. Giving full power to the motor
Korndorfer starter, closed transition:
contactor 3 closes
small time delay
contactor 3 closes. Giving a reduced voltage to the motor
time delay
contactor 3 opens. The transformer is now acting as a choke
small time delay
contactor 2 closes. The transformer is now shorted between it’s incoming and % tappings. But as it's the same potential bewteen the two points there is no current flow
small time delay
contactor 1 opens.
As can you see the sequence for the Korndorfer puts stress on the transformer where it has to withstand acting as a choke. So for small motors it’s uneconomical.
Last edited by a moderator:
OP
Knobhead
Re: Dahlander Motors
I hadn’t intended to cover these so soon but the thread about a roller shutter door prodded me to go ahead. I’ve only ever got involved with 2 of these motors, and in all honesty I hope I never see one again!
The motor for the roller shutter door would be drawing 2.
The Dahlander motor is a two speed motor that offers a 1 : 2 speed switching. It is a specially wound pole switching motor requiring a special dual speed starter.
The Dahlander motor is wound as a star motor or a delta motor with centre taps on each leg of the winding. The motor is connected in star or delta for one speed and in "double star" for the other speed.The starter requires three contactors (five for reversing), a speed 1 main contactor and a speed 2 main contactor and a star contactor that can differ in it’s connection depending on the motor layout. Two over load protection relays are required, one in series with each of the main contactors.
Dahlander motors can be wound for constant power, variable torque or constant torque applications.A constant power Dahlander motor is would as a delta motor, and a constant torque motor is wound as a star.I’ve done the drawings showing reversing starters as this is what I used to work on.
View attachment 9135
View attachment 9134
This is a simplified version of the above.
View attachment 9142
View attachment 9133
I hadn’t intended to cover these so soon but the thread about a roller shutter door prodded me to go ahead. I’ve only ever got involved with 2 of these motors, and in all honesty I hope I never see one again!
The motor for the roller shutter door would be drawing 2.
The Dahlander motor is a two speed motor that offers a 1 : 2 speed switching. It is a specially wound pole switching motor requiring a special dual speed starter.
The Dahlander motor is wound as a star motor or a delta motor with centre taps on each leg of the winding. The motor is connected in star or delta for one speed and in "double star" for the other speed.The starter requires three contactors (five for reversing), a speed 1 main contactor and a speed 2 main contactor and a star contactor that can differ in it’s connection depending on the motor layout. Two over load protection relays are required, one in series with each of the main contactors.
Dahlander motors can be wound for constant power, variable torque or constant torque applications.A constant power Dahlander motor is would as a delta motor, and a constant torque motor is wound as a star.I’ve done the drawings showing reversing starters as this is what I used to work on.
View attachment 9135
View attachment 9134
This is a simplified version of the above.
View attachment 9142
View attachment 9133
Last edited by a moderator:
OP
Knobhead
Correction to post#7
Korndorfer starter, closed transition:
contactor 3 closes
small time delay
contactor 1 closes. Giving a reduced voltage to the motor
time delay
contactor 3 opens. The transformer is now acting as a choke
small time delay
contactor 2 closes. The transformer is now shorted between it’s incoming and % tappings. But as it's the same potential bewteen the two points there is no current flow
small time delay
contactor 1 opens.
Korndorfer starter, closed transition:
contactor 3 closes
small time delay
contactor 1 closes. Giving a reduced voltage to the motor
time delay
contactor 3 opens. The transformer is now acting as a choke
small time delay
contactor 2 closes. The transformer is now shorted between it’s incoming and % tappings. But as it's the same potential bewteen the two points there is no current flow
small time delay
contactor 1 opens.
OP
Knobhead
Star delta overloads
View attachment 9231
The motor needs overload protection via an overload unit, with a S/D starter the O/L’s can be placed in the circuit in two different positions. With a DOL starter the setting is simple, just set at the FLC of the motor.
Method “B” is the preferred method as it provides the correct O/L protection during starting. The disadvantage is the setting of the O/L unit. In a S/D starter only a proportion of the current flows through the O/L unit, therefore the relay has to be set at 0.58 (1/√3) of the FLC. Not quite so simple.
At times there are advantages to method “A”. I’ve used it for starting very heavy inertia loads where there would be a risk of tripping during start up. Some early starters even shorted the O/L’s out all together.
View attachment 9231
The motor needs overload protection via an overload unit, with a S/D starter the O/L’s can be placed in the circuit in two different positions. With a DOL starter the setting is simple, just set at the FLC of the motor.
Method “B” is the preferred method as it provides the correct O/L protection during starting. The disadvantage is the setting of the O/L unit. In a S/D starter only a proportion of the current flows through the O/L unit, therefore the relay has to be set at 0.58 (1/√3) of the FLC. Not quite so simple.
At times there are advantages to method “A”. I’ve used it for starting very heavy inertia loads where there would be a risk of tripping during start up. Some early starters even shorted the O/L’s out all together.
Last edited by a moderator:
OP
alli
Thanks for this thread, really interesting.
Do you ever sleep? 03:31 AM
Do you ever sleep? 03:31 AM
OP
Knobhead
Insomnia
View attachment 9236
View attachment 9236
OP
alli
Sorry to hear that, I guess that's why your drawings are superb.
OP
silva.foxx
To supplement Tony's SD info Line and Delta contactors are sized at 58% flc and the Star contactor at 33% flc of the motor load.
For example: a 220kw 3ph AC induction motor pulling say, 360 amps and star-delta started. Line and Delta contactors to be sized min. 210 amps and Star contactor at 120 amps. So you'd use 2off 250 and 1off 140A contactors (assuming AC-3 inductive requirement) as opposed to 3off 400A contactors. This saves on both expense and panel space.
On much smaller motors this is less of an issue and you'd typically find the three contactors similarly, if not indentically, sized.
For example: a 220kw 3ph AC induction motor pulling say, 360 amps and star-delta started. Line and Delta contactors to be sized min. 210 amps and Star contactor at 120 amps. So you'd use 2off 250 and 1off 140A contactors (assuming AC-3 inductive requirement) as opposed to 3off 400A contactors. This saves on both expense and panel space.
On much smaller motors this is less of an issue and you'd typically find the three contactors similarly, if not indentically, sized.
OP
Knobhead
Slip Ring or Wound Rotor Motors
View attachment 9616
View attachment 9617
I’ve had a love / hate relationship with these motors for years. Maintenance of the brush-gear is a pain to any maintenance department. Overlook or ignore it and it comes back and bites you. Excessive carbon dust can cause flashover on start up. On initial start up the voltage on the rings is at it’s maximum (some motors I’ve worked on could have up to 3KV between them). Carbon dust will find it’s way in to any little crevice, let it build up enough and you can expect an explosion. The first picture shows a basic set up, the left side shows a “standard” brush box, the right a constant force box. The second picture shows a practical set up. The constant force box uses a spring similar to the ones used for cable earthing but in this case they are trying to un-coil.
View attachment 9618
View attachment 9619
The slip ring or wound rotor motor is an induction machine where the rotor comprises a set of coils that are terminated in sliprings to which external impedances can be connected. The stator is the same as is used with a standard squirrel cage motor.
View attachment 9620
By changing the impedance connected to the rotor circuit, the speed/current and speed/torque curves can be altered.
The slip ring motor is used primarily to start a high inertia load or a load that requires a very high starting torque across the full speed range. By correctly selecting the resistors used in the secondary resistance or slip ring starter, the motor is able to produce maximum torque at a relatively low current from zero speed to full speed. A secondary use of the slip ring motor, is to provide a means of speed control. Because the torque curve of the motor is effectively modified by the resistance connected to the rotor circuit, the speed of the motor can be altered. Increasing the value of resistance on the rotor circuit will move the speed of maximum torque down. If the resistance connected to the rotor is increased beyond the point where the maximum torque occurs at zero speed, the torque will be further reduced.
When used with a load that has a torque curve that increases with speed, the motor will operate at the speed where the torque developed by the motor is equal to the load torque. Reducing the lad will cause the motor to speed up, and increasing the load will cause the motor to slow down until the load and motor torque are equal. Operated in this manner, the slip losses are dissipated in the secondary resistors and can be very significant. The speed regulation is also very poor.
Motor Characteristics.
The Slip Ring motor has two distinctly separate parts, the stator and the rotor. The stator circuit is rated as with a standard squirrel cage motor and the rotor is rated in frame voltage and short circuit current. The frame voltage is the open circuit voltage when the rotor is not rotating and gives a measure of the turns ratio between the rotor and the stator. The short circuit current is the current flowing when the motor is operating at full speed with the slip rings (rotor) shorted and full load is applied to the motor shaft.
Secondary Resistance Starters.
The secondary resistance starter comprises a contactor to switch the stator and a series of resistors that are applied to the rotor circuit and gradually reduced in value as the motor accelerates to full speed. The rotor would normally be shorted out once the motor is at full speed. The resistor values are selected to provide the torque profile required and are sized to dissipate the slip power during start. The secondary resistors can be metallic resistors such as wound resistors, plate resistors or cast resistors.
View attachment 9621
Or they can be liquid resistors made up of saline solution or caustic soda or similar, provided there is sufficient thermal mass to absorb the total slip loss during start.
View attachment 9622
View attachment 9623
I worked on the same type of liquid starter shown in the photograph. They were obsolete and costing a fortune to have final contacts made for them. £2500 for a set of contacts was a bit OTT, so I came up with this idea, standard Telemecanique 315A contactors working at 1.7X their normal rated voltage. The final contact in the original design were slow making so at 1250A they didn’t last long, with my set up the contacts were high speed and so didn’t get eroded. The final load current dropped from 400A+ to 150A @11KV.
View attachment 9624
To select the values of the resistors, you need to know the frame voltage and the short circuit current. The maximum torque occurs approximately at the point where the rotor reactance equals the termination resistance. The final stage of the resistance should always be designed for a maximum torque close to full speed to prevent a very large step in current when shorting the final stage of resistance. If a single stage was used and the maximum torque occurred at 50% speed, then motor may accelerate to 60% speed, depending on the load. If the rotor was shorted at this speed, the motor would draw a very high current (typically around 1400% FLC) and produce very little torque, and would most probably stall!
High Inertia Loads
Slip ring motors are commonly used on high inertia loads because of their superior start efficiencies and their ability to withstand the inertia of the loads
When a load is started, the full speed kinetic energy of that load is dissipated in the rotor circuit. With a standard cage type induction motor, there only some motors that can be used on high inertia loads. Most will suffer rotor damage due to the power dissipated by the rotor. With the slip ring motor, the secondary resistors can be selected to provide the optimum torque curves and they can be sized to withstand the load energy without failure.
Starting a high inertia load with a standard cage motor would require between 400% and 550% start current for up to 60 seconds. Starting the same machine with a wound rotor motor (slip ring motor) would require around 200% current for around 20 seconds. A much more efficient solution.
Shorting the rings out on a slip ring motor with a high inertia load is not an option as the load energy must be dissipated in the rotor winding during start. This will cause insulation failure in the rotor circuit.
Now this is my idea of a resonable sized motor
View attachment 9625
View attachment 9616
View attachment 9617
I’ve had a love / hate relationship with these motors for years. Maintenance of the brush-gear is a pain to any maintenance department. Overlook or ignore it and it comes back and bites you. Excessive carbon dust can cause flashover on start up. On initial start up the voltage on the rings is at it’s maximum (some motors I’ve worked on could have up to 3KV between them). Carbon dust will find it’s way in to any little crevice, let it build up enough and you can expect an explosion. The first picture shows a basic set up, the left side shows a “standard” brush box, the right a constant force box. The second picture shows a practical set up. The constant force box uses a spring similar to the ones used for cable earthing but in this case they are trying to un-coil.
View attachment 9618
View attachment 9619
The slip ring or wound rotor motor is an induction machine where the rotor comprises a set of coils that are terminated in sliprings to which external impedances can be connected. The stator is the same as is used with a standard squirrel cage motor.
View attachment 9620
By changing the impedance connected to the rotor circuit, the speed/current and speed/torque curves can be altered.
The slip ring motor is used primarily to start a high inertia load or a load that requires a very high starting torque across the full speed range. By correctly selecting the resistors used in the secondary resistance or slip ring starter, the motor is able to produce maximum torque at a relatively low current from zero speed to full speed. A secondary use of the slip ring motor, is to provide a means of speed control. Because the torque curve of the motor is effectively modified by the resistance connected to the rotor circuit, the speed of the motor can be altered. Increasing the value of resistance on the rotor circuit will move the speed of maximum torque down. If the resistance connected to the rotor is increased beyond the point where the maximum torque occurs at zero speed, the torque will be further reduced.
When used with a load that has a torque curve that increases with speed, the motor will operate at the speed where the torque developed by the motor is equal to the load torque. Reducing the lad will cause the motor to speed up, and increasing the load will cause the motor to slow down until the load and motor torque are equal. Operated in this manner, the slip losses are dissipated in the secondary resistors and can be very significant. The speed regulation is also very poor.
Motor Characteristics.
The Slip Ring motor has two distinctly separate parts, the stator and the rotor. The stator circuit is rated as with a standard squirrel cage motor and the rotor is rated in frame voltage and short circuit current. The frame voltage is the open circuit voltage when the rotor is not rotating and gives a measure of the turns ratio between the rotor and the stator. The short circuit current is the current flowing when the motor is operating at full speed with the slip rings (rotor) shorted and full load is applied to the motor shaft.
Secondary Resistance Starters.
The secondary resistance starter comprises a contactor to switch the stator and a series of resistors that are applied to the rotor circuit and gradually reduced in value as the motor accelerates to full speed. The rotor would normally be shorted out once the motor is at full speed. The resistor values are selected to provide the torque profile required and are sized to dissipate the slip power during start. The secondary resistors can be metallic resistors such as wound resistors, plate resistors or cast resistors.
View attachment 9621
Or they can be liquid resistors made up of saline solution or caustic soda or similar, provided there is sufficient thermal mass to absorb the total slip loss during start.
View attachment 9622
View attachment 9623
I worked on the same type of liquid starter shown in the photograph. They were obsolete and costing a fortune to have final contacts made for them. £2500 for a set of contacts was a bit OTT, so I came up with this idea, standard Telemecanique 315A contactors working at 1.7X their normal rated voltage. The final contact in the original design were slow making so at 1250A they didn’t last long, with my set up the contacts were high speed and so didn’t get eroded. The final load current dropped from 400A+ to 150A @11KV.
View attachment 9624
To select the values of the resistors, you need to know the frame voltage and the short circuit current. The maximum torque occurs approximately at the point where the rotor reactance equals the termination resistance. The final stage of the resistance should always be designed for a maximum torque close to full speed to prevent a very large step in current when shorting the final stage of resistance. If a single stage was used and the maximum torque occurred at 50% speed, then motor may accelerate to 60% speed, depending on the load. If the rotor was shorted at this speed, the motor would draw a very high current (typically around 1400% FLC) and produce very little torque, and would most probably stall!
High Inertia Loads
Slip ring motors are commonly used on high inertia loads because of their superior start efficiencies and their ability to withstand the inertia of the loads
When a load is started, the full speed kinetic energy of that load is dissipated in the rotor circuit. With a standard cage type induction motor, there only some motors that can be used on high inertia loads. Most will suffer rotor damage due to the power dissipated by the rotor. With the slip ring motor, the secondary resistors can be selected to provide the optimum torque curves and they can be sized to withstand the load energy without failure.
Starting a high inertia load with a standard cage motor would require between 400% and 550% start current for up to 60 seconds. Starting the same machine with a wound rotor motor (slip ring motor) would require around 200% current for around 20 seconds. A much more efficient solution.
Shorting the rings out on a slip ring motor with a high inertia load is not an option as the load energy must be dissipated in the rotor winding during start. This will cause insulation failure in the rotor circuit.
Now this is my idea of a resonable sized motor
View attachment 9625
Last edited by a moderator:
OP
SirKit Breaker
Tony's posts always make good reading, he really knows his stuff. Any apprentices out there in the industrial field could do a lot worse than read through a lot of his posts. i know a few of mine have.
Cheers.......Howard
Cheers.......Howard
OP
Knobhead
Motor bearings
Before I start on this I want to know who would be interested in motor bearings.
Glennispark is willing to help on this subject, between us I think we’ve well over 60 years of experience to hand, hopefully others will add to the pool.
Please say Yay or Ney as it does take time to do drawings to make things clear.
Before I start on this I want to know who would be interested in motor bearings.
Glennispark is willing to help on this subject, between us I think we’ve well over 60 years of experience to hand, hopefully others will add to the pool.
Please say Yay or Ney as it does take time to do drawings to make things clear.
OP
alli
Re: Motor bearings
I would really appreciate a post on bearings, if you can afford the time.
I would really appreciate a post on bearings, if you can afford the time.
- Reaction score
- 1,597
Re: Motor bearings
id like to learn more about the effects of VSD's on bearings, and common solutions ect. I think Marvo has mentioned that hes encountered this problem before.
I along with others appreciate the time taken to write these threads.
id like to learn more about the effects of VSD's on bearings, and common solutions ect. I think Marvo has mentioned that hes encountered this problem before.
I along with others appreciate the time taken to write these threads.
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