AUTOMATIC SYNCHRONIZING CONTROL SYSTEM

• US 3,794,846 A
• Filed: 09/18/1972
• Issued: 02/26/1974
• Est. Priority Date: 09/18/1972
• Status: Expired due to Term

• Current Assignee: GEC Automation Projects Incorporated
• Original Assignee: David W. Schlicher, Denton C. Rowe
• Inventors: Schlicher, David W., Rowe, Denton C.
• Primary Examiner(s): Trammell, James D.
• Application Number:
  US05/289,791
• Time in Patent Office: 526 Days
• Field of Search: 307/87 322/24,28,32
• US Class Current: 307/87
• CPC Class Codes: H02J 3/42 with automatic parallel connection when synchronisation is achieved

Abstract

An accurate, miniaturized synchronizing system for automatically connecting an oncoming AC generator in parallel with a threephase bus source when the generator and bus source output parameters are simultaneously within predetermined phase, frequency and voltage synchronization limits of each other, and for automatically changing the rotational speed and voltage of the oncoming generator to achieve the predetermined synchronizing conditions. Sensing circuits monitor the oncoming generator and bus source output voltages. Pulse generator circuits produce a plurality of phase angle dependent pulse train signals from the sensed output voltage signals. A digital speed matching circuit determines the directional frequency difference between the oncoming generator and bus source signals and provides periodic compensating speed regulating signals to a prime mover of the oncoming generator in response thereto. A voltage matching circuit detects voltage synchronization unbalance between the oncoming generator and bus source output signals, and in response thereto, provides a digital output synchronization signal indicative of the voltage synchronization unbalance, and provides voltage matching control signals to a voltage regulator of the oncoming generator. Phase and frequency synchronizer logic circuits digitally compare the generated pulse train signals and provide therefrom logical phase and frequency synchronization output signals indicative of the phase and frequency unbalance between the oncoming generator and bus source output signals. A synchronizer control logic circuit provides an energizing signal to a circuit breaker for connecting the oncoming generator in parallel with the bus source when the voltage, phase and frequency synchronization output signals simultaneously indicate that the oncoming generator and bus source outputs are within the predetermined synchronization limits. A lockout circuit prevents repeated circuit breaker closure attempts if the circuit breaker fails to close after receiving the first energizing signal from the synchronizer control logic circuit.

Claims

1. Apparatus for determining phase and frequency synchronization of two electric AC sources comprising:

a. means connected to sense output voltages of first and second AC sources for providing first and second AC sensed output signals respectively in response thereto;

b. means operatively connected to receive said first and second AC sensed signals for respectively producing therefrom a plurality of first and second source binary pulse train signals having pulse repetition rates directly proportionAl to the frequencies of said first and second sensed AC signals respectively and having individual pulse widths independent of the frequencies of said sensed signals and representative respectively of a predetermined number of first and second source phase angle degrees; and

c. digital circuit means connected to receive said plurality of first and second source binary pulse train signals for detecting time coincidence between pulses from selected pulse trains of said first and second pulse train signals and for providing in response thereto;

1. phase output signals indicative of phase angle matching, within a predetermined allowable phase matching range, between said first and second AC sensed signals, and 2. frequency output signals indicative of frequency matching, within a predetermined allowable frequency matching range, between said first and second AC sensed signals.

2. Apparatus for determining phase and frequency synchronization of two electrical AC sources accordign to claim 1, including circuit means operatively connected to receive said phase and frequency output signals of said digital circuit means and operable in one state for producing a first output signal when said received phase and frequency signals simultaneously indicate said phase and frequency matching, and operable in another state for producing a second output signal different from said first output signal when said received phase and frequency signals do not simultaneously indicate said phase and frequency matching.

3. Apparatus for determining phase and frequency synchronization of two electrical AC sources according to claim 1, wherein said means for producing said plurality of first and second source binary pulse train signals includes means for providing first and second source phase angle pulse train signals each characterized by pulses of constant predetermined width and similarly positioned in phase relationship to the zero degree phase angle reference points respectively of said first and second AC source sensed signals;

and wherein said digital circuit means includes logic gate means connected to receive said first and second source phase angle pulse train signals operable in one mode for producing a first phase output signal when pulses from said first and second phase angle pulse train signals are coincidentally received thereby and operable in another mode for producing a second phase output signal different from said first output signal when pulses from said first and second phase angle pulse train signals are not coincidentally received thereby.

4. Apparatus for determining phase and frequency synchronization of two electrical AC sources according to claim 1, wherein said means for producing said plurality of first and second source binary pulse train signals includes means for providing at least one pair of pulse train signals for determining said frequency matching, wherein said pair of pulse train signals comprises a first pulse train signal having pulses of constant predetermined width and a pulse repetition rate directly proportional to the frequency of said first AC source sensed signal, and a second pulse train signal having pulses of constant predetermined width and a pulse repetition rate directly proportional to the frequency of said second AC source sensed signal;

and wherein said digital circuit means includes a frequency synchronization detecting circuit comprising;

a. logical circuit means operatively connected to receive said pair of pulse train signals for producing in response thereto a first output signal whenever pulses from said first and second output pulse train signals are coincidentally received and for producing a second output signal whenever pulses from said first and second pulse train signals are not coincidentally received; and

b. timing circuit means operatively connected to receive said first and second output signals for measuring the continuous time duration of said received second oUtput signal, wherein said timing circuit means is normally operative in a first mode to produce a first output frequency signal when said first output signal is received and when said second output signal is continuously received for a time less than a predetermined period of time, and is operative in a second mode to produce a second frequency output signal different from said first output signal after said second output signal has been continuously received for a length of time greater than said predetermined period of time.

5. Apparatus for determining phase and frequency synchronization of two electrical AC sources according to claim 4, including circuit means for producing a periodic reset output signal whose frequency is proportional to one of said first and second AC sensed signals, and wherein said timing circuit means includes means connected to receive said reset output signal for causing in response thereto said timing circuit means when operating in its second mode to resume operation in its first mode.

6. An improved automatic synchronizing apparatus for connecting an oncoming AC generator source in parallel with an energized AC bus source comprising:

a. sensing means for sensing corresponding output voltages of said generator and said bus sources, and for respectively providing sensed generator and bus AC output signals in response thereto;

b. means operatively connected to receive said sensed generator and bus signals for respectively producing therefrom a plurality of binary generator and bus output pulse train signals;

c. phase synchronizer gating means operatively connected to receive at least one each of said generator and bus binary output pulse train signals, for digitally comparing said received binary pulse train signals and for producing in response thereto a binary phase output signal, wherein said phase synchronizer gating means is operable to cause said binary phase output signal to assume first and second binary output levels respectively when said generator and bus sensed signals are and are not simultaneously within a predetermined number of phase angle degrees of each other;

d. frequency synchronizer circuit means operatively connected to receive at least one each of said generator and bus binary output pulse train signals for digitally comparing the frequencies thereof and for producing in response thereto a binary frequency output signal, wherein said frequency synchronizer circuit means is operable to cause said binary frequency output signal to assume first and second binary output levels respectively when the frequencies of said sensed bus and generator signals are and are not within a predetermined frequency synchronization range of each other;

e. voltage synchronizer circuit means operatively connected to receive said sensed generator and bus AC output signal for comparing the voltage levels of said received sensed signals and for producing in response thereto a binary voltage output signal, wherein said voltage synchronizer circuit means is operable to cause said voltage binary output signal to assume first and second binary output levels respectively when said received sensed voltage levels are and are not within a predetermined voltage synchronization range of each other;

f. synchronizer control circuit means operatively connected to receive said binary phase, frequency and voltage output signals for producing a synchronizing output signal;

said synchronizer control means being operable in a first state to produce a first level synchronizing output signal whenever said first binary levels of said phase, frequency and voltage output signals are simultaneously received, and operable in a second state to produce a second level synchronizing output signal whenever one or more of said second binary levels of said phase, frequency and voltage output signals is received; and

g. switching circuit means operatively connected to said generator and bus sources and for receiving said synchroniZing output signal, normally operable upon receipt of said first level synchronizing signal in an open mode for electrically isolating said bus and oncoming generator sources, and operable in a closed mode upon receipt of said second level synchronizing signal for electrically connecting in parallel said bus and generator sources.

7. An improved automatic synchronizing apparatus for connecting an oncoming AC generator source in parallel with an energized AC bus source according to claim 6, wherein said means for producing said plurality of pulse train signals includes means for causing each of said plurality of binary generator output pulse train signals to be characterized by pulse repetition rates directly proportional to the frequency of said sensed generator AC signal and by individual pulses of constant predetermined width within any given pulse train signal, and further includes means for causing each of said binary bus output pulse train signals to be characterized by a pulse repetition rate directly proportional to the frequency of said sensed bus AC signal and by individual pulses of constant predetermined width within any given pulse train signal.

8. An improved automatic synchronizing apparatus for connecting an oncoming AC generator source in parallel with an energized AC bus source according to claim 6, wherein said sensing means produces generally sinusoidal sensed generator and bus AC output signals and wherein said means for producing said plurality of bus and generator output pulse train signals comprises:

a. bus and generator wave shaper circuit means operatively connected to receive respectively said sinusoidal bus and generator sensed AC signals and for respectively shaping said received bus and generator sensed signals for producing squared bus and generator output signals having frequencies respectively equal to said received bus and generator sensed signals;

b. bus pulse generating cicuit means operatively connected to receive said square bus output signal for producing in response thereto said plurality of binary bus output pulse train signals, each having a pulse repetition rate equal to the frequency of said squared bus signal and having pulses whose widths equal a predetermined number of phase angle degrees of said squared bus signal and are constant for individual pulse train signals; and

c. generator pulse generating circuit means operatively connected to receive said squared generator output signal for producing in response thereto said plurality of binary generator pulse train signals, each having a pulse repetition rate equal to the frequency of said squared generator output signal and having pulses whose widths equal a predetermined number of phase angle degrees of said squared generator signal and are constant for individual pulse train signals.

9. An improved automatic synchronizing apparatus for connecting an oncoming AC generator source in parallel with an energized AC bus source according to claim 7, wherein said means for producing said plurality of bus and generator output pulse train signals include means for producing a bus and a generator angle pulse train signal each having individual pulses whose leading edges are respectively time coincident with like phase angle reference points of said sensed bus and generator signals and whose widths are constant and equal respectively a predetermined number of bus and generator phase angle degrees;

and wherein said phase synchronizer gating means is operatively connected to receive said bus and generator angle pulse train signals for detecting coincidence in time of pulses from said bus and generator angle pulse train signals, and for producing in response thereto said binary phase output signal.

10. An improved automatic synchronizing apparatus for connecting an oncoming AC generator source in parallel with an energized AC bus source according to claim 9, wherein said phase synchronizer gating means includes a coincident gating circuiT operatively connected for receiving said bus and generator angle pulse train signals for producing therefrom said binary phase output signal, said coincident gating circuit being operable in one mode to cause said binary phase output signal to assume said first binary output level when pulses from said bus and generator angle pulse train signals are simultaneously received, and operable in a second mode to cause said binary phase output signal to assume said second binary output level when pulses from said bus and generator angle pulse train signals are not simultaneously received.

11. An improved automatic synchronizing apparatus for connecting an oncoming AC generator source in parallel with an energized AC bus source according to claim 10, wherein said phase synchronizer gating means includes pulse stretching means operatively connected to receive said binary phase output signal for altering said binary phase output signal so as to expand the time duration at which it appears at said second binary level.

12. An improved automatic synchronizing apparatus for connecting an oncoming AC generator source in parallel with an energized AC bus source according to claim 7, wherein said means for producing said plurality of binary generator and bus output pulse train signals include means for producing generator slip timing and bus reference marker pulse train signals each being characterized by pulses of constant widths and having leading pulse edges that are respectively time coincident with a predetermined fixed phase angle of said sensed generator and bus signals;

wherein individual pulses from said generator slip timing and said bus reference marker pulse train signals when coincident in time, define a slip angle timing zone whose real time period varies with the relative frequencies of said sensed generator and bus signals; and

wherein said frequency synchronizer circuit means includes means operatively connected to receive said generator slip timing and said bus reference marker pulse train signals for detecting and measuring the time coincidence of pulses from said received signals and for varying in response thereto said binary frequency output signal.

13. An improved automatic synchronizing apparatus for connecting an oncoming AC generator source in parallel with an energized AC bus source according to claim 9, wherein said means for producing said plurality of binary bus and generator output pulse train signals include means for producing bus slip timing and generator reference marker pulse train signals each characterized by pulses of constant predetermined widths and having pulse leading edges respectively time coincident with a predetermined fixed phase angle of said sensed bus and generator signals;

wherein respective pulses from said bus slip timing and generator reference marker pulse train signals when coincident in time, define a first periodic slip angle timing zone whose real time period varies with the relative frequencies of said sensed generator and bus signals; and

wherein said frequency synchronizer circuit means includes means operatively connected to receive said bus slip timing and generator reference marker pulse train signals for detecting and measuring the time coincidence of pulses from said received signals and for varying in response thereto said binary frequency output signal.

14. An improved automatic synchronizing apparatus for connecting an oncoming AC generator source in parallel with an energized AC bus source according to claim 13, wherein said means for producing said plurality of binary generator and bus output pulse train signals include means for producing generator slip timing and bus reference marker pulse train signals each being characterized by pulses of constant width having pulse leading edges respectively time coincident with a predetermined fixed phase angle of said sensed generator and bus signals;

wherein respective pulses from said generator slip timing an said bus reference marker pulse train signals When time coincident, define a second slip angle timing zone whose real time period varies with the relative frequencies of said sensed generator and bus signals; and

wherein said frequency synchronizer circuit means includes means operatively connected to receive said generator slip timing and said bus reference marker pulse train signals for measuring the time coincidence of pulses from said received signals and for varying in response thereto said binary frequency output signal.

15. An improved automatic synchronizing apparatus for connecting an AC generator source in parallel with an energized AC bus source according to claim 14, including means colectively connecting said bus and generator slip timing, reference marker and angle pulse train signal producing means for causing synchronous operation thereof such that the leading pulse edges of said bus and generator marker pulse train signals are time coincident respectively with the leading edges of said bus and generator amgle pulse train signals, and the leading pulse edges of said bus generator slip timing pulse train signals respectively trail in time the trailing pulse edges respectively of said bus and generator angle pulse train signals;

and wherein said frequency synchronizer circuit means includes;

a. input logic means operatively connected to receive pulses of said bus and generator reference marker and slip timing pulse train signals, for detecting time coincidence therebetween and for producing in response thereto an output enable signal whenever pulses either from said bus reference marker and said generator slip timing signals or from said generator reference marker and said bus slip timing signals are simultaneously received, and for producing a disable output signal whenever said reference marker and slip timing signals are not simultaneously received;

b. timing circuit means operatively connected to receive said enable and disable signals for providing a timer output signal in response thereto, said timing circuit means operable to produce a first timer output signal whenever said disable signal is received or said enable signal is received for a length of time less than a preset time interval, and operable to produce a second timer output signal, differing from said first timer output signal, after said enable signal has been continuously received for a length of time longer than said preset time interval; and

c. latching circuit means having first input means operatively connected to receive said first and second timer output signals and second input means adapted to receive a reset signal for producing said binary frequency output signal;

said latching circuit means operable to vary said binary frequency output signal in response to said received input signals for causing said binary frequency output signal to assume said second binary level whenever said second timer output signal or a reset signal are respectively received by said first and second input means, and operable to cause said binary frequency output signal to assume said first binary output level when said second timer output signal is received by said first input means.

16. An improved automatic synchronizing apparatus for connecting an oncoming AC generator source in parallel with an energized AC bus source according to claim 15, wherein said bus and generator angle pulse train producing means include means for causing the leading pulse edges of said bus and generator angle pulse train signals to be respectively time coincident with the zero degree phase angle reference points of said bus and generator sensed AC signals;

wherein said means for producing said plurality of binary generator output pulse train signals include means for producing an out of phase reference pulse train signal having binary pulses whose leading edges are time coincident with a definite phase angle reference point of said sensed generator signal, said definite phase angle reference point being out of phase with that said phase angle point to which pulses from said angle pulse train signals are referenced; and

including means operatively connecting said reset input means of said latching circuit means to receive said out of phase reference pulse train signal as said reset signal.

17. An improved automatic synchronizing apparatus for connecting an oncoming AC generator source in parallel with an energized AC bus source according to claim 6, including lock-out circuit means having an input connected to receive said synchronizing output signal, normally operable in a first state upon receipt of said first level synchronizing output signal for producing an enabling lock-out output signal and operable in a second locking state upon receipt of said second level synchronizing output signal for thereafter producing a second lock-out output signal;

and wherein said synchronizer control circuit means further contains means operatively connected to receive said enabling and second lock-out output signals for causing said synchronizer control means to become operable in its first state to produce said first level synchronizing output signal whenever said phase, frequency and voltage first binary levels and said enabling lockout output signals are simultaneously received and to become operable in its second state to produce said second level synchronizing output signal whenever one or more of said phase, frequency and voltage second binary levels or said second lockout output signal is received.

18. An improved automatic synchronizing apparatus for connecting an oncoming AC generator source in parallel with an energized AC bus source according to claim 6, including speed matching circuit means operatively connected to receive said plurality of binary generator and bus output pulse train signals for effecting in response thereto changes in the output signal frequency of said oncoming generator in a direction causing the frequency of said sensed generator output signal to approach that of said sensed bus output signal.

19. An improved automatic synchronizing apparatus for connecting an oncoming AC generator source in parallel with an energized AC bus source according to claim 18, wherein said speed matching circuit means for effecting said change in the oncoming generator frequency by providing pulsed output raise and lower output signals for controlling speed regulating motor means of said oncoming generator source.

20. An improved automatic synchronizing apparatus for connecting an oncoming AC generator source in parallel with an energized AC bus source according to claim 19, wherein said means for producing said plurality of binary bus and generator pulse train signals includes means for producig said bus and generator pulse train signals having pulse repetition rates respectively equal to the frequencies of said sensed bus and generator signals, means for producing bus and generator reference marker pulse train signals each having pulses whose leading edges are time coincident respectively with like pahse angles of said sensed bus and generator signals, and means for producing bus and generator speed sensing pulse train signals each having pulses whose leading edges are time coincident respectively with like phase angles of said sensed bus and generator signals;

and wherein said speed matching circuit means includes;

a. low frequency sensing logic means operatively connected to receive said bus reference marker and said generator speed sensing pulse train signals for producing in response thereto a logical low frequency output signal when pulses from said bus reference and said generator speed sensing signals are simultaneously received;

b. high frequency sensing logic means operatively connected to receive said generator reference and said bus speed sensing pulse train signals for producing in response thereto a logical high frequency output signal when pulses from said generator reference and said bus speed sensing signals are simultaneously received; and

c. drive circuIt means operatively connected to receive said logical high frequency and low frequency output signals for producing respectively therefrom said lower and raise output signals.

21. An improved automatic synchronizing apparatus for connecting an oncoming AC generator source in parallel with an energized AC bus source according to claim 20, wherein said low frequency sensing logic means includes means for causing said logical high frequency output signal to assume first and second binary output levels respectively when pulses from said generator reference and said bus speed sensing pulse train signals are and are not simultaneously received;

and wherein said drive circuit means includes means for producing said lower output signal when said high frequency output signal assumes its first output level and to produce said raise output signal when said low frequency output signal assumes its first output level.

22. An improved automatic synchronizing apparatus for connecting an oncoming AC generator source in parallel wtih an energized AC bus source according to claim 21, wherein said drive circuit means includes first timing circuit means operatively connected to produce a first timing signal for controlling the pulse width of individual pulses of said raise and lower output signals.

23. An improved automatic synchronizing apparatus for connecting an oncoming AC generator source in parallel with an energized AC bus source according to claim 22, including circuit means operatively connected to receive selected signals from said plurality of binary generator and bus output pulse train signals and for producing a triggering signal in response thereto;

and wherein said drive circuit means includes inhibiting circuit means connected to receive as inputs said low and high frequency binary logic output signals and said triggering signals for inhibiting said raise and lower output pulse signals in response to said triggering signal.

24. An improved automatic synchronizing apparatus for connecting an oncoming AC generator source in parallel with an energized AC bus source according to claim 23, wherein said means for producing said plurality of generator binary output pulse train signals includes means for producing an out of phase pulse train signal having pulses whose leading edges periodically occur at time intervals so as to be out of phase with the leading pulse edges of said generator reference marker pulse train signal;

wherein said circuit means for producing said triggering signal comprises conicident gating means operatively connected to receive said generator out of phase and said bus reference marker pulse train signals for producing said triggering signal when pulses from said generator out of phase and said bus reference pulse train signals are simultaneously received, and wherein said inhibiting circuit means includes;

a. first AND logic gate means connected to receive as inputs said binary low frequency output and said triggering signals, for producing a first AND gate output signal when said low frequency output signal appearing at said first level is received simultaneously with said triggering signals;

b. second AND logic gate means connected to receive as inputs said binary high frequency and said triggering signals, for producing a second AND gate output signal when said high frequency output signal appearing at said first level is received simultaneously with said triggering signal;

c. raise speed latch circuit means operatively connected to receive said first AND gate output signal and said first timing signal for producing, when enabled by said first AND gate output signal, said raise output pulse signal in response to said first timing signal; and

d. lower speed latch circuit means operatively connected to receive said second AND gate output signal and said first timing signal for producing, when enabled by said second AND gate output signal, said lower output pulse signal in response to said fIrst timing signal.

25. An improved automatic synchronizing apparatus for connecting an oncoming AC generator source in parallel with an energized AC bus source according to claim 24, including second timing means having an enable input operatively connected to receive said first timing signal, said second timing means being operable when enabled by said first timing signal for producing a second timing signal delayed in time from receipt of said first timing enabling signal by a first preset time interval;

wherein said inhibiting circuit means also includes gating means operatively connected to receive as inputs said second timing signal and said triggering signal for providing a triggering output signal upon receiving said second timing signal or said triggering signal; and

wherein said triggering signal received as an input by said first and second AND logic gate means comprises said gate triggering output signal.

26. An improved automatic synchronizing apparatus for connecting an oncoming AC generator source in parallel with an energized AC bus source according to claim 25, including means operatively connecting said first timing circuit means to receive as enabling inputs said raise and lower signals, and wherein said first timing circuit means includes means for causing said first timing signal to be produced delayed in time from the receipt of said raise or lower enabling source by a second preset adjustable time interval.

27. An improved automatic synchronizing apparatus for connecting an oncoming AC generator source in parallel with an energized AC bus source according to claim 25, including means collectively connecting said bus and generator reference and speed sensing pulse train signal producing means for causing synchronous operation thereof such that the leading pulse edges of said bus and generator reference pulse train signals are time coincident respectively with first predetermined like phase angles of said sensed bus and generator AC signals, the leading pulse edges of said bus and generator speed sensing pulse train signals are respectively time coincident with said first predetermined like phase angles of sensed bus and generator AC signals, and the leading pulse edges of said generator reference pulse train signal are time coincident with a second predetermined phase angle of said sensed generator AC signal;

said second phase angle differing from said first phase angle by approximately 180*.

28. An improved automatic synchronizing apparatus for connecting an oncoming AC generator source in parallel with an energized AC bus source according to claim 6, wherein said voltage synchronizer means includes voltage matching circuit means connected to receive said sensed bus and generator output voltages for producing in response thereto output voltage matching signals for effecting a change in the output voltage level of said oncoming generator in a direction causing the sensed generator output voltage to approach that of said sensed bus output.

29. An improved automatic synchronizing apparatus for connecting an oncoming AC generator source in parallel with an energized AC bus source according to claim 28, wherein said synchronizing apparatus includes voltage regulating means connected to receive said voltage matching signals for raising and lowering the output voltage level of said oncoming generator source in response thereto.

30. An improved automatic synchronizing apparatus for connecting an oncoming AC generator source in parallel with an energized AC bus source according to claim 28, wherein said voltage synchronizer means includes:

a. input circuit means for producing averaged bus and generator signals respectively from said sensed bus and generator output signals;

b. control circuit means operatively connected to receive said averaged bus and generator signals for selectively producing at its output one of said averaged signals shifted in magnitude by a predetermined voltage increMent;

c. comparator means operatively connected to receive said averaged bus and generator signals and the incremented averaged signal for producing first and second comparator output signals in response thereto; and

d. output circuit means operatively connected to receive said first and second comparator output signals for producing in response thereto said binary voltage output signal and said output matching signals.

31. An improved automatic synchronizing apparatus for connecting an oncoming AC generator source in parallel with an energized AC bus source according to claim 30, wherein said input means comprises voltage transducer circuit means operatively connected to receive said bus and generator sensed output voltage signals for producing respectively therefrom averaged bus and generator current analog signals.

32. An improved automatic synchronzing apparatus for connecting an oncoming AC generator source in parallel with an energized AC bus source according to claim 31, wherein said voltage transducer means includes first and second voltage transducers each having input transistor and filtering circuits, said voltage transducer means being operatively connected for respectively receiving said sensed bus and generator signals and for producing said bus and generator current analog signals in response thereto.

33. An improved automatic synchronizing apparatus for connecting an oncoming AC generator source in parallel with an energized AC bus source according to claim 30, wherein said control circuit means includes means for adjusting said predetermined voltage increment level within a predetermined voltage tolerance band, said adjustment within the tolerance band defining said voltage synchronization range.

34. An improved automatic synchronizing apparatus for connecting an oncoming AC generator source in parallel with an energized AC bus source according to claim 33, wherein said control circuit means includes:

a. level detecting means connected to receive said averaged bus and generator signals for providing a detected output signal proportional to the larger of said received averaged bus and generator signals; and

b. range control circuit means operatively connected to receive said detector output signal for algebraically incrementing said detected output signal by said predetermined voltage increment level.

35. An improved automatic synchronizing apparatus for connecting an oncoming AC generator source in parallel with an energized AC bus source according to claim 30, wherein said comparator means includes first and second comparator amplifier circuit means;

said first comparator amplifier circuit means being operatively connected to receive said incremented averaged and said bus averaged signals for comparing same and for producing said first comparator output signal in response thereto;

said second comparator amplifier circuit means being operatively connected to receive said incremented averaged and said generator averaged signals for comparing same for producing said second comparator output signal in response thereto.

36. An improved automatic synchronizing apparatus for connecting an oncoming AC generator source in parallel with an energized AC bus source according to claim 35, wherein said control circuit means includes means for producing said incremented averaged output signal by subtracting said predetermined voltage increment level from the larger of said averaged bus or generator signals;

wherein said first comparator amplifier circuit means includes means for producing said first comparator output signal when the voltage of said incremented averaged signal exceeds that of said received averaged bus signal; and

wherein said second comparator amplifier circuit means includes means for producing said second comparator output signal when the voltage of said incremented averaged signal exceeds that of said received averaged generator signal.

37. An improved automatic synchronizing apparAtus for connecting an oncoming AC generator source in parallel with an energized AC bus source according to claim 30, wherein said voltage matching circuit means includes means for producing said raise and lower voltage output signals which comprise said output matching signals;

and wherein said output means includes raise and lower relay driving circuit means operatively connected respectively to receive said first and second comparator signals for producing continuous raise or lower output signals respectively in response thereto.

38. An improved automatic synchronizing apparatus for connecting an oncoming AC generator source in parallel with an energized AC bus source according to claim 30, wherein said output means includes transistor means connected to sense said first and second comparator output signals for producing said first binary output voltage level when said first and second comparator signals are simultaneously below a threshold level, and for producing said second binary voltage output signal level when said first and second comparator signals are above said threshhold level.