US3226558A - Automatic control systems - Google Patents

Automatic control systems Download PDF

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Publication number
US3226558A
US3226558A US255774A US25577463A US3226558A US 3226558 A US3226558 A US 3226558A US 255774 A US255774 A US 255774A US 25577463 A US25577463 A US 25577463A US 3226558 A US3226558 A US 3226558A
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United States
Prior art keywords
speed
program
drive means
signal generator
turbine
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Expired - Lifetime
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US255774A
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English (en)
Inventor
Walker Herbert Oswald
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Richardsons Westgarth and Co Ltd
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Richardsons Westgarth and Co Ltd
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    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
    • G05D13/00—Control of linear speed; Control of angular speed; Control of acceleration or deceleration, e.g. of a prime mover
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D19/00—Starting of machines or engines; Regulating, controlling, or safety means in connection therewith
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D21/00—Shutting-down of machines or engines, e.g. in emergency; Regulating, controlling, or safety means not otherwise provided for
    • F01D21/02—Shutting-down responsive to overspeed
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P23/00—Arrangements or methods for the control of AC motors characterised by a control method other than vector control
    • H02P23/16—Controlling the angular speed of one shaft

Definitions

  • This invention relates to automatic control systems for controlling the operation of rotary machines such as steam turbines.
  • the invention is particularly applicable to the control of these machines during their starting-up period.
  • the starting-up of large steam turbines is frequently controlled through a control system which regulates the operation of the turbine up to the point where the normal running control gear takes over, the regulation being achieved by using a device which compares the actual speed of the turbine shaft at any instant which the intended speed set by speed-programme apparatus. If for any reason the actual turbine speed departs by more than a limited amount from the intended speed laid down by the programme, some kind of over-ride control can come into action so that the turbine is shut down for correction of the fault which caused the actual speed to depart from the intended speed.
  • the departure of the turbine speed from its intended value is due to a temporary factor which does not warrant shutting down the turbine.
  • the speed of the turbine may drop during its starting-up period due to a temporary restriction of the steam supply which is corrected in a relatively short time.
  • a difficulty which arises however if the turbine is kept running under such conditions is that, when the turbine speed lags behind the programme speed to an appreciable extent, the programme must not be allowed to continue as if there had been no such lag in speed, for this would cause a sudden upward surge in the turbine speed on removal or correction of the cause of the speed-lag which could result in serious damage. This in fact is the reason why over-ride controls are provided in the systems used hitherto so that the turbine is shut down on the occurrence of any undesirable departure in speed.
  • a control system in accordance with the invention therefore includes means which are capable of overcoming the difficulty outlined above, and according to the invention an automatic control system for controlling the operation of a rotary machine comprises speed-sensitive means for detecting non-permissible departures in the speed of the machine from the intended speed, and an adjusting device for adjusting speed-programme apparatus which determines the intended speed so that, on the removal or correction of the factor which caused the actual speed to depart from its intended value, the speed programme recommences at an adjusted intended speed which is not different to a harmful extent from the actual speed of the machine at that instant.
  • a similar control system can be used to control the rate of loading of the alternator after it has been synchronised with the electrical network to which it is connected.
  • a control system for this purpose will accordingly have load-sensitive means and load-programme apparatus instead of speed-sensitive 3,226,558 Patented Dec. 28, 1965 means and speed-programme apparatus, the load-sensitive means being arranged to detect non-permissible departures in the load on the machine from the intended load.
  • FIGURE 1 is a speed/time graph
  • FEGURE 2 is a diagrammatic layout of the control system
  • FIGURE 3 is another speed/time graph.
  • the line AB in FIGURE 1 represents the intended speed of a steam turbine during its starting-up period, the point B being that at which the normal running control gear takes over.
  • the lines ab on either side of the line AB represent the maximum limits by which the actual speed of the turbine may depart from its intended speed without endangering the machine. In a typical case a deviation of about rpm. from the intended speed is permissible.
  • FIGURE 2 illustrates one particular control system by which the speed programme is adjusted to take into account temporary departures of the turbine speed from its intended value.
  • a speed-sensitive device 10 arranged on or near the steam turbine 12 being controlled serves to feed an electrical signal F2 proportional to or dependent on the actual speed of the turbine shaft back to an algebraic summing device 26 such as a summing amplifier which compares the signal with an electrical reference signal F1 received from a program speed signal generator 16 to derive a difference or error signal which is applied over line 28 to the input of a servo amplifier 14.
  • an algebraic summing device 26 such as a summing amplifier which compares the signal with an electrical reference signal F1 received from a program speed signal generator 16 to derive a difference or error signal which is applied over line 28 to the input of a servo amplifier 14.
  • the signal F1 is a variable signal representing the desired or program speed of the turbine shaft at any instant, and provided the relationship between the two signals F1 and F2 is such that the actual speed of the turbine shaft is above the lower line ab on the graph shown in FIGURE 1, the difference or error signal applied to the servo amplifier 14 is below the threshold value necessary to activate the servo and the servo will remain out of action.
  • the program speed signal generator 16 is driven by the combination of a servo amplifier 24 and servometer 22 so as to deliver a program speed signal that increases progressively with time along the curve AB of FIGURES 1 and 3. In the absence of any interruption in the speed I programme, the actual speed of the turbine shaft will 3 approximately follow the line AB shown in FIGURES 1 and 3.
  • the actual speed signal F2 will immediately drop in relation to the program speed signal F1, and directly the difference between the two signals exceeds an amount corresponding to the distance between the line AB and the lower line ab in FIGURE 3, the input to the servo amplifier 14 exceeds the aforesaid threshold value thereof and the amplifier commences to supply a driving signal F3 to an associated servo motor 18 which serves to drive the program speed signal generator in the opposite direction to the drive imparted by the servomotor 22.
  • the two drives from the two servomotors 22, 18 may be combined by differential gearing (not shown) and thence applied to the program speed signal generator 16 as a single drive input.
  • the signal F1 representing the program speed of the turbine will be adjusted to a value I which brings the actual turbine speed at the point K back within the permissible deviation from the adjusted programme (see FIGURE 3).
  • the dilference signal on the input lead 28 falls back below the threshold value of the amplifier 14, the servomotor 18 ceases to drive, and program speed signal generator 16 resumes its normal forward programme but from the adjusted value I.
  • the actual turbine speed again lags behind by more than the permissible amount, and the servo amplifier 14 once more brings the servo motor 18 into operation to make a further program speed adjustment. This cyclical process will continue until the steam supply becomes normal again.
  • the line KH representing the actual turbine speed approximately coincides with the line cd representing the maximum permissible deviation from the adjusted program line I M.
  • the adjusted program speed M will not differ to a harmful extent from the actual speed H of the turbine at that instant. In other words, the turbine will not be required to speed up to a dangerous extent which would have been the case had the programme not been adjusted to compensate for the temporary loss in steam.
  • the programme and the turbine speed now follow the line MN.
  • the control system includes apparatus 20 of conventional construction to control the steam supply to the turbine 12 in accordance with the signal F1 received from the program speed generator 16 and the signal F2 representing actual turbine speed.
  • the program speed signal generator 16 will generally take the form of a variable ratio transformer with a movable top or wiper driven by the servo motor 22 under the control of the servo amplifier 24.
  • control system described above is primarily concerned with the control of a steam turbine, but the invention is applicable to the control of other rotary machines such as gas turbines, electric motors and alternators.
  • Apparatus for controlling the operation of a steam turbine during start-up and in accordance with a desired program of increasing turbine shaft speed comprising: an actual speed signal generator sensing actual turbine shaft speed and deriving a first variable signal representative thereof, a program speed signal generator and first drive means therefor, said program speed signal generator deriving a second variable signal that normally increases progressively during turbine start-up and is representative of the desired program speed at each time instant, comparator means receiving said first and second signals as inputs and deriving an error signal representative of the instantaneous difference between actual speed and program speed, a second drive means coupled to said program speed signal generator which second drive means is ordinarily inactive, and servo means responsive to said error signal and applying a driving signal to said second drive means whenever said error signal exceeds a predetermined limit value, said second drive means imparting drive to said program speed signal generator in opposite sense to said first drive means.
  • Apparatus for controlling the operation of a rotary machine during a period of varying output and in accordance with a program of desired change of a selected output parameter comprising: a signal generator sensing the actual instantaneous value of said output parameter and deriving a first variable signal representative thereof, a program signal generator and first drive means therefor, said program signal generator deriving a second variable signal representative of the desired value of said output parameter at each time instant, comparator means receiving said first and second signals as inputs and deriving an error signal representative of the instantaneous difference between the actual value and the program value of said parameter, a second drive means coupled to said program signal generator which second drive means is ordinarily inactive, and servo means responsive to said error signal and applying a driving signal to said second drive means whenever said error signal exceeds a predetermined limit value, said second drive means imparting drive to said program signal generator in a direction to reduce the difference between said first and second signals.
  • Apparatus for controlling the operation of a rotary machine during start-up and in accordance with a program of desired increase of a selected output parameter comprising: a signal generator sensing the actual instantaneous value of said output parameter and deriving a first variable signal representative thereof, a program signal generator and first drive means therefor, said program signal generator deriving a second variable signal that normally increases progressively during start-up and is representative of the desired value of said output parameter at each time instant, comparator means receiving said first and second signals as inputs and deriving an error signal representative of the instantaneous difference between the actual value and the program value of said parameter, a second drive means coupled to said program signal generator which second drive means is ordinarily inactive, and servo means responsive to said error signal and applying a driving signal to said second drive means whenever said error signal exceeds a predetermined limit value, said second drive means driving said program signal generator in a direction opposite to said first drive means.
  • Apparatus for controlling the operation of a rotary machine during a period of varying output and in accordance with a program of desired change of a selected output parameter comprising: a signal generator sensing the actual instantaneous value of said output parameter and deriving a first variable signal representative thereof, a program signal generator deriving a second variable signal representative of the desired value of said output parameter at each time instant, comparator means receiving said first and second signals as inputs and deriving an error signal representative of the instantaneous difference between the actual value and the program value of said parameter, and program-adjusting means coupled to said program signal generator and having said error signal applied thereto as an input said program-adjusting means remaining inactive while said error signal is below a preselected limit value but effecting program-adjusted in said program signal generator in the sense necessary to bring the error signal back below the limit if said limit is exceeded.
  • Apparatus according to claim 1 further comprising control means receiving as inputs said first and second variable signals and operative to vary the steam input to the turbine in response thereto.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Automation & Control Theory (AREA)
  • Control Of Turbines (AREA)
US255774A 1962-02-05 1963-02-04 Automatic control systems Expired - Lifetime US3226558A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB4340/62A GB1037173A (en) 1962-02-05 1962-02-05 Improvements in or relating to automatic control systems

Publications (1)

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US3226558A true US3226558A (en) 1965-12-28

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US255774A Expired - Lifetime US3226558A (en) 1962-02-05 1963-02-04 Automatic control systems

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US (1) US3226558A (enrdf_load_stackoverflow)
CH (1) CH408055A (enrdf_load_stackoverflow)
GB (1) GB1037173A (enrdf_load_stackoverflow)
NL (1) NL288491A (enrdf_load_stackoverflow)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3348559A (en) * 1964-04-07 1967-10-24 Baldwin Lima Hamilton Corp Electronic governor
US3601984A (en) * 1969-10-27 1971-08-31 Gen Electric Temperature rate control system

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1971811A (en) * 1933-07-20 1934-08-28 Gen Electric Control system
US1994121A (en) * 1933-02-16 1935-03-12 Gen Electric Elastic fluid turbine
US2285208A (en) * 1940-04-10 1942-06-02 Gen Electric Automatic turbine control system
US2671860A (en) * 1947-06-26 1954-03-09 Bendix Aviat Corp Load sensitive fuel governor for gas turbines
US2743097A (en) * 1953-08-25 1956-04-24 Leeds & Northrup Co Generator loading rate control
US2783427A (en) * 1953-07-10 1957-02-26 W L Maxson Corp Motor control systems
US2790092A (en) * 1955-06-09 1957-04-23 Thompson Prod Inc Alternator drive starting control
US2926681A (en) * 1955-05-31 1960-03-01 Rotol Ltd Speed governing systems for turbines
GB907438A (en) * 1959-02-25 1962-10-03 Siemens Ag A control circuit for the speed regulation of an electric motor

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1994121A (en) * 1933-02-16 1935-03-12 Gen Electric Elastic fluid turbine
US1971811A (en) * 1933-07-20 1934-08-28 Gen Electric Control system
US2285208A (en) * 1940-04-10 1942-06-02 Gen Electric Automatic turbine control system
US2671860A (en) * 1947-06-26 1954-03-09 Bendix Aviat Corp Load sensitive fuel governor for gas turbines
US2783427A (en) * 1953-07-10 1957-02-26 W L Maxson Corp Motor control systems
US2743097A (en) * 1953-08-25 1956-04-24 Leeds & Northrup Co Generator loading rate control
US2926681A (en) * 1955-05-31 1960-03-01 Rotol Ltd Speed governing systems for turbines
US2790092A (en) * 1955-06-09 1957-04-23 Thompson Prod Inc Alternator drive starting control
GB907438A (en) * 1959-02-25 1962-10-03 Siemens Ag A control circuit for the speed regulation of an electric motor

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3348559A (en) * 1964-04-07 1967-10-24 Baldwin Lima Hamilton Corp Electronic governor
US3601984A (en) * 1969-10-27 1971-08-31 Gen Electric Temperature rate control system

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Publication number Publication date
GB1037173A (en) 1966-07-27
CH408055A (de) 1966-02-28
NL288491A (enrdf_load_stackoverflow) 1900-01-01

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