US3832609A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Slip detection system
Assignee: Woodward Inc
•
Filing: 1973-02-05
•
Granted: 1974-08-27
•
Expires: 1993-02-05
Abstract
Abstract A system for detecting excessive slip between the speed of an ac. motor and the speed of an a-c. generator supplying power to the motor at a variable frequency. Transducers associated with the motor and the generator produce pulses at frequencies proportional to the speeds of the motor and the generator, respectively. The periods Tm and Tg of these two series of pulses are measured by applying clock pulses to a counter during each period, so that the number of clock pulses counted during each period is proportional to the duration thereof. The pulses applied to the counter during the period Tm are counted up, and the pulses applied during the period Tg are counted down, so that the resulting output of the counter represents the difference (Tm - Tg). The count representing the period Tm is stored in a separate register, and the number representing Tm is then repetitively subtracted from the number representing (Tm - Tg) until the remainder is reduced to zero. The number of subtraction steps required to reduce the remainder to zero is counted to provide a number representing the quotient (Tm -Tg)/Tm. This quotient represents the per cent slip of the motor, and is compared with a preselected per cent slip limit determined by the setting of a series of thumbwheel switches. If the measured per cent slip value exceeds the preselected limit, an output signal is generated for actuating an alarm or other suitable utilization device so that the excessive slip condition can be corrected. Computation of the actual per cent slip is carried out by digital signal processing on a rapidly iterating basis so that the system provides a substantially instantaneous indication of any change in the percent slip. The system includes a number of auxiliary features for detecting various malfunctions and for resetting the system in response to both internal and external command signals.
Inventors
- 👤 W Barrett
- 👤 H Green
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 19:48
CPC Classifications
H; H02; H02P; H02P23/00; H02P23/08; G; G01; G01P; G01P3/00; G01P3/42; G01P3/56; G01P3/60; G06; G06F; G06F7/00; G06F7/60; G06F7/62
Claims Analysis
Total Claims: 42
Claim 1
Independent Claim
159 words
A system for detecting excessive slip between the speed of an a-c. motor and the speed of an a-c. generator supplying power to said motor at a variable frequency, said system comprising the combination of a. means for generating a first electrical signal representing the speed of the generator, b. means for generating a second electrical signal representing the speed of the motor, c. means for generating a third electrical signal representing a preselected maximum limit for the percentage of slip between said generator and said motor, d. computing means responsive to said first and second signals for producing an electrical output signal representing K(Ng Nm)/Ng where K is a predetermined constant, Ng is the generator speed, and Nm is the motor speed, e. and means responsive to said third signal and said output signal for producing an excess slip output signal whenever the value represented by said output signal exceeds the preselected limit represented by said third signal.
Claim 2
Independent Claim
159 words
A system for detecting excessive slip between the speed of an a-c. motor and the speed of an a-c. generator supplying power to said motor at a variable frequency, said system comprising the combination of a. means for generating a first electrical signal representing the speed of the generator, b. means for generating a second electrical signal representing the speed of the motor, c. means for generating a third electrical signal representing a preselected maximum limit for the percentage of slip between said generator and said motor, d. computing means responsive to said first and second signals for producing an electrical output signal representing K(Ng Nm)/Ng where K is a predetermined constant, Ng is the generator speed, and Nm is the motor speed, e. and means responsive to said third signal and said output signal for producing an excess slip output signal whenever the value represented by said output signal exceeds the preselected limit represented by said third signal.
Claim 3
Dependent Claim
56 words
A system for detecting excessive slip as set forth in claim 1 wherein said means for generating said first electrical signal comprises means for generating pulses at a frequency proportional to the generator speed, and said means for generating said second electrical signal comprises means for generating pulses at a frequency proportional to the motor speed.
Claim 4
Dependent Claim
29 words
means responsive to said second signal for producing an electrical signal digitally representing a number proportional to the duration of the period Tm between pulses in said second signal,
Claim 5
Dependent Claim
29 words
means responsive to said second signal for producing an electrical signal digitally representing a number proportional to the duration of the period Tm between pulses in said second signal,
Claim 6
Dependent Claim
38 words
means responsive to said signals digitally representing numbers proportional to (Tm - Tg) and Tm for repetitively subtracting the number proportional tO Tm from the number proportional to (Tm - Tg) until the remainder is reduced to zero,
Claim 7
Dependent Claim
38 words
means responsive to said signals digitally representing numbers proportional to (Tm - Tg) and Tm for repetitively subtracting the number proportional tO Tm from the number proportional to (Tm - Tg) until the remainder is reduced to zero,
Claim 8
Dependent Claim
16 words
and means for counting the number of subtraction steps required to reduce said remainder to zero.
Claim 9
Dependent Claim
16 words
and means for counting the number of subtraction steps required to reduce said remainder to zero.
Claim 10
Dependent Claim
23 words
and means responsive to said Tg and Tm signals for producing an electrical signal digitally representing a number proportional to K(Tm - Tg)/Tm.
Claim 11
Dependent Claim
23 words
and means responsive to said Tg and Tm signals for producing an electrical signal digitally representing a number proportional to K(Tm - Tg)/Tm.
Claim 12
Dependent Claim
17 words
A system for detecting excessive slip as set forth in claim 2 wherein said computing means includes
Claim 13
Dependent Claim
104 words
A system for detecting excessive slip as set forth in claim 3 wherein said means for producing said signal representing a number proportional to K(Tm - Tg)/Tm includes a source of clock pulses, an up-down counter having count-up and count-down input terminals and an output terminal, means for applying said clock pulses to the count-up input terminal of said counter during the period Tm, and means for applying said clock pulses to the count-down input terminal of said counter during the period Tg for producing an electrical signal at the counter output terminal digitally representing a number proportional to the difference (Tm - Tg).
Claim 14
Dependent Claim
29 words
A system for detecting excessive slip as set forth in claim 3 wherein said means for producing said signal digitally representing a number proportional to K(Tm - Tg)/Tm comprises
Claim 15
Dependent Claim
62 words
A system for detecting excessive slip as set forth in claim 5 wherein said means for producing said signal representing a number proportional to (Tm - Tg) includes an up-down counter, and means for recycling an electrical signal digitally representing the remainder from each of the repetitive subtraction steps to said counter for use as the minuend in the next subtraction step.
Claim 16
Dependent Claim
75 words
A system for detecting excessive slip as set forth in claim 5 wherein said means for repetitively subtracting the number proportional to Tm from the number proportional to (Tm - Tg) comprises means for producing an electrical signal digitally representing the two''s complement of a binary number proportional to Tm, and adding means for producing an electrical signal digitally representing the sum of said two''s complement and a binary number proportional to (Tm - Tg).
Claim 17
Dependent Claim
61 words
A system for detecting excessive slip as set forth in claim 7 wherein said adding means is a binary adder having a carry output, and including an electronic counter connected to said carry output for counting the number of addition steps which yield a carry to produce an electrical signal digitally representing a number proportional to the quotient (Tm - Tg)/Tm.
Claim 18
Dependent Claim
33 words
A system for detecting excessive slip as set forth in claim 1 wherein said means for generating said third signal includes a set of manually operable switch means for selecting said maximum limit.
Claim 19
Dependent Claim
33 words
A system for detecting excessive slip as set forth in claim 1 wherein said means for producing an excess slip signal comprises a comparator for comparing said third signal and said output signal.
Claim 20
Dependent Claim
66 words
A system for detecting excessive slip as set forth in claim 2 which includes means for producing a start signal in response to generation of the first pulse in said second signal within a predetermined interval following generation of the first pulse in said first signal, and means for activating a utilization device in response to the absence of said start signal after said predetermined interval.
Claim 21
Dependent Claim
28 words
A slip detection system as set forth in claim 5 which includes overflow detection means for activating a utilization device in response to an overflow of said counter.
Claim 22
Dependent Claim
54 words
A slip detection system as set forth in claim 1 which includes means for monitoring said signals representing the speeds of the motor and generator, means for producing an output signal in response to termination of either of said speed-representing signals, and means for activating a utilization device in response to said output signal.
Claim 23
Dependent Claim
60 words
A slip detection system as set forth in claim 1 which includes internal reset means for automatically resetting said system at the end of each cycle of operation of said computing means, and means responsive to production of said excess slip signal prior to the resetting operation for maintaining said excess slip signal during and subsequent to the resetting operation.
Claim 24
Dependent Claim
36 words
A slip detection system as set forth in claim 1 which includes external reset means responsive to a command signal for resetting the entire slip detection system including the means for producing said excess slip signal.
Claim 25
Dependent Claim
33 words
A slip detection system as set forth in claim 1 which includes means responsive to the absence of either of said speed-representing signals at start-up of the system for activating a utilization device.
Claim 26
Independent Claim
298 words
A system for signaling the percentage difference between two recurring signals having variable periods, said system comprising the combination of a. an up-down counter having a count-up input terminal, a count-down input terminal, and output terminals carrying electrIcal signals digitally representing the number contained in the counter, b. a source of clock pulses, c. means responsive to a first one of said recurring signals for applying said clock pulses to said count-up input terminal during one period of said first signal to produce counter output signals digitally representing a number Tm proportional to the duration of said one period of said first signal, d. means responsive to the second recurring signal for applying said clock pulses to said count-down input terminal during one period of said second signal to produce counter output signals digitally representing a number K(Tm - Tg) proportional to the difference between the durations of the periods of said first and second signals, e. subtracting means responsive to said output signals digitally representing said numbers Tm and K(Tm - Tg) for producing output signals digitally representing the difference K(Tm - Tg) - Tm, f. means for repetitively applying said difference output signals from said subtracting means and said signals representing said number Tm to said subtracting means until the output signals therefrom represent a zero difference, g. a source of clock pulses generated at the same frequency at which said difference output signals are repetitively applied to said subtracting means, h. and an electronic counter for counting the clock pulses from source (g) and producing output signals digitally representing the number of subtraction operations required to reduce the difference represented by the output signals from said subtracting means to zero, whereby the output signals from said counter digitally represent the quotient of K(Tm - Tg)/Tm.
Claim 27
Independent Claim
298 words
A system for signaling the percentage difference between two recurring signals having variable periods, said system comprising the combination of a. an up-down counter having a count-up input terminal, a count-down input terminal, and output terminals carrying electrIcal signals digitally representing the number contained in the counter, b. a source of clock pulses, c. means responsive to a first one of said recurring signals for applying said clock pulses to said count-up input terminal during one period of said first signal to produce counter output signals digitally representing a number Tm proportional to the duration of said one period of said first signal, d. means responsive to the second recurring signal for applying said clock pulses to said count-down input terminal during one period of said second signal to produce counter output signals digitally representing a number K(Tm - Tg) proportional to the difference between the durations of the periods of said first and second signals, e. subtracting means responsive to said output signals digitally representing said numbers Tm and K(Tm - Tg) for producing output signals digitally representing the difference K(Tm - Tg) - Tm, f. means for repetitively applying said difference output signals from said subtracting means and said signals representing said number Tm to said subtracting means until the output signals therefrom represent a zero difference, g. a source of clock pulses generated at the same frequency at which said difference output signals are repetitively applied to said subtracting means, h. and an electronic counter for counting the clock pulses from source (g) and producing output signals digitally representing the number of subtraction operations required to reduce the difference represented by the output signals from said subtracting means to zero, whereby the output signals from said counter digitally represent the quotient of K(Tm - Tg)/Tm.
Claim 28
Dependent Claim
51 words
A system as set forth in claim 17 wherein said subtracting means comprises means for producing electrical signals digitally representing the two''s complement of a binary number Tm, and adding means for producing an electrical signal digitally representing the sum of said two''s complement and a binary number K(Tm - Tg).
Claim 29
Dependent Claim
63 words
A system as set forth in claim 18 wherein said adding means is a binary adder having a carry output for producing a carry output signal as long as said sum is greater than zero, and including means responsive to said carry output signal for applying the clock pulses from source (g) to said counter only until said sum is reduced to zero.
Claim 30
Independent Claim
157 words
A method for detecting excessive slip between the speed of an a-c. motor and the speed of an a-c. generator supplying power to said motor at a variable frequency, said method comprising the steps of a. generating a first electrical signal representing the speed of the generator, b. generating a second electrical signal representing the speed of the motor, c. generating a third electrical signal representing a preselected maximum limit for the percentage of slip between said generator and said motor, d. producing an electrical signal in response to said first and second signals and representing K(Ng - Nm)/Ng where K is a predetermined constant, Ng is the generator speed, and Nm is the motor speed, e. rapidly iterating steps (a) through (d), f. and producing an excess slip signal in response to said third signal and said output signal whenever the value represented by said output signal exceeds the preselected limit represented by said third signal.
Claim 31
Independent Claim
157 words
A method for detecting excessive slip between the speed of an a-c. motor and the speed of an a-c. generator supplying power to said motor at a variable frequency, said method comprising the steps of a. generating a first electrical signal representing the speed of the generator, b. generating a second electrical signal representing the speed of the motor, c. generating a third electrical signal representing a preselected maximum limit for the percentage of slip between said generator and said motor, d. producing an electrical signal in response to said first and second signals and representing K(Ng - Nm)/Ng where K is a predetermined constant, Ng is the generator speed, and Nm is the motor speed, e. rapidly iterating steps (a) through (d), f. and producing an excess slip signal in response to said third signal and said output signal whenever the value represented by said output signal exceeds the preselected limit represented by said third signal.
Claim 32
Dependent Claim
42 words
A method for detecting excessive slip as set forth in claim 20 wherein said first signal comprises pulses generated at a frequency proportional to the generator speed, and said second signal comprises pulses generated at a frequency proportional to the motor speed.
Claim 33
Dependent Claim
76 words
A method for detecting excessive slip as set forth in claim 21 including the steps of producing an electrical signal digitally representing a number proportional to the period Tg between pulses in said first signal, producing an electrical signal digitally representing a number proportional to the period Tm between pulses in said second signal, and producing an electrical signal digitally representing a number proportional to K(Tm - Tg)/Tm in response to said Tg and Tm signals.
Claim 34
Dependent Claim
82 words
A method for detecting excessive slip as set forth in claim 22 wherein said signal representing a number proportional to K(Tm - Tg)/Tm is produced by generating a series of clock pulses, applying said clock pulses to the count-up input terminal of an up-down counter during the period Tm, and applying said clock pulses to the count-down input terminal of said counter during the period Tg for producing an electrical signal digitally representing a number proportional to the difference (Tm - Tg).
Claim 35
Dependent Claim
77 words
A method for detecting excessive slip as set forth in claim 22 wherein said signal representing a number proportional to K(Tm - Tg)/Tm is produced by generating an electrical signal digitally representing a number proportional to the difference (Tm - Tg), repetitively subtracting the number proportional to Tm from the number proportional to (Tm - Tg) until the remainder is reduced to zero, and counting the number of subtraction steps required to reduce said remainder to zero.
Claim 36
Dependent Claim
58 words
A method for detecting excessive slip as set forth in claim 24 wherein the repetitive subtraction is carried out by producing an electrical signal digitally representing the two''s complement of a binary number proportional to Tm, and producing an electrical signal digitally representing the sum of said two''s complement and a binary number proportional to (Tm - Tg).
Claim 37
Dependent Claim
32 words
A method for detecting excessive slip as set forth in claim 24 wherein the remainder from each of the repetitive subtraction steps is used as the minuend in the next subtraction step.
Claim 38
Dependent Claim
36 words
A method for detecting excessive slip as set forth in claim 24 which includes the step of activating a utilization device in response to the counting of a number of subtraction steps above a predetermined limit.
Claim 39
Dependent Claim
39 words
A method for detecting excessive slip as set forth in claim 25 wherein the signal representing a number proportional to the quotient (Tm - Tg)/Tm is generated by counting the number of binary addition steps which yield a carry.
Claim 40
Dependent Claim
65 words
A method for detecting excessive slip as set forth in claim 21 which includes the steps of producing a start signal in response to generation of the first pulse in said second signal within a predetermined interval following generation of the first pulse in said first signal, and activating a utilization device in response to the absence of said start signal after said predetermined interval.
Claim 41
Dependent Claim
53 words
A method for detecting excessive slip as set forth in claim 20 which includes the steps of monitoring said signals representing the speeds of the motor and generator, producing an output signal in response to termination of either of said speed-representing signals, and activating a utilization device in response to said output signal.
Claim 42
Dependent Claim
34 words
A method for detecting excessive slip as set forth in claim 20 which includes the step of activating a utilization device in response to the absence of either of said speed-representing signals at start-up.
References Cited (Backward Citations)
US2848671A
Cited
US2928033A
Cited
US3206665A
Cited
US3372323A
Cited
US3408549A
Cited
US3700986A
Cited
US3694634A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-08-26 | 1978-02-25 | 1978-08-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-08-26 | 1982-02-25 | 1982-08-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-08-26 | 1986-02-25 | 1986-08-27 | $7700.00 | Window Closed / Lapsed |