US 3517177 A
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Description (OCR text may contain errors)
June 23, 1970 w. H. .CROWELL 3,
EQUIVALENT BASE LOAD HOURS COMPUTER Filed Dec. 15, '19s? DRIVER COUNTE R g? INVENTOR, WILLIAM H. CROWELL ATTORNEY.
United States Patent Otfice 3,517,177 EQUIVALENT BASE LOAD HOURS COMPUTER William H. Crowell, Lansdale, Pa., assignor to Honeywell Inc., Minneapolis, Minn., a corporation of Delaware Filed Dec. 15, 1967, Ser. No. 690,891 Int. Cl. G06g 7/18; 7/64; G011 3/00 US. Cl. 235183 8 Claims ABSTRACT OF THE DISCLOSURE It is well known that most prime movers have determinable useful operating lives. The useful operating life is defined as the life during which the prime mover may operate prior to either breakdown or maintenance. The useful operating life is a function of many variables of the physical system. For example, the output load driven and/ or produced by the prime mover, the temperature of the physical system, the pressure relative to the physical system and the like are typical variables of a physical system. The useful operating life of such a prime mover is established as a number of hours of operation under a set of standard or optimized conditions and is identified as the Base Load of the machine. It is axiomatic that the machine will not always be operated at the Base Load condition. A variation from any or several of the standard conditions produces a calculable variation in the number of hours of the useful operating life of the machine. Such a shift in the useful operating life is identified as the Equivalent Base Load Hours. Accordingly, these variables may be operated upon individually or together to produce a mathematical expression of the operating life of the prime mover.
Because of the last mentioned relationship, it--is desirable to be able to compute the consumption or the rate of consumption of the useful life of the prime mover under operating conditions. This information is used so that the prime mover is not overloaded or excessively operated under undesirable conditions. Moreover, the prime mover is not removed from useful production and overhauled prior to the actual necessity thereof if the useful life of the prime mover has not been fully utilized.
Therefore, the subject invention relates to a computer which manipulates input signals in accordance with a mathematical expression of the measurable variable such that the rate of consumption of the useful operating life of a prime mover can be monitored. In a preferred embodiment, the computer utilizes a plurality of amplifiers for producing and/or summing the various expressions of constants and/or measurable variables, a time division multiplier for producing a signal representative of the equivalent base load on the prime mover, time integration means for selectively operating upo the rate signals to produce an indication of the percentage of operating life which has been consumed. In addition, a switching circuit is utilized to selectively include a simulated base load signal if the actual operational load is below a minimum value.
Consequently, one object of this invention is to provide a base load computing circuit.
Another object of this invention is to provide a computing circuit which indicates the consumption of useful operating life of a prime mover.
Another object of this invention is to provide a com- 3,517,177 Patented June 23, 1970 puting circuit wherein the operation of a prime mover is detected and rated for purposes such as billing or maintenance or the like.
These and other objects and advantages of this invention will become more readily apparent when the following description is read in conjunction with the single figure which is a schematic diagram of the computing circuit.
Referring now to the drawing, the schematic diagram includes amplifiers 1, 2 and 3 which are connected as linear amplifiers having a predetermined loop gain. In addition, amplifier 4 is connected as an integrating amplifier while amplifier Sis connected as a comparator.
More specifically, variable resistor 10 is connected between a +15 volt source and ground. The variable tap of resistor 10 is connected via fixed resistor 11 and variable resistor 12 to the input of amplifier 1. Variable resistor 12 is connected such that the resistance thereof in series with resistor 11, may be varied. The output of amplifier 1 is connected via normally open contacts K2B and resistor 14 to the input of amplifier 1. Normally closed contacts K2A and temperature sensitive resistor 13 are also connected between the output and the input of amplifier 1.
The coil K2 associated with contacts K2A and K2B are connected to switch 40- and source 39. Thus, by closing switch 40 during the calibration operation, coil K2 is energized. When energized, coil K2 causes contacts K2A to open and contacts K2B to close. It should be noted that resistor 14 is a precision resistor which is equal to the resistance of temperature sensitive resistor 13 at a predetermined temperature. Therefore, when in the calibration mode, resistor 12 is varied such that the loop gain of amplifier 1 is unity. That is, resistor 12 is set equal to the resistance of resistor 14 whereby unity gain of amplifier 1 at the predetermined base temperature is achieved.
Resistor 13, a temperature sensitive resistor, may be a high precision nickel probe. This type of probe exhibits extreme sensitivity and accuracy in measuring temperature. Since it is frequently desirable to measure the temperature of a physical system relating to a prime mover at a fixed predetermined temperature, the resistance value of the probe at the predetermined temperature is calculated and used during calibration. The output of amplifier 1 is connected via coupling resistor 15 to summing junction 37 at the input of amplifier 3.
Variable resistor 17 is connected between a +15 volt source and ground. The variable tap of resistor 17 is connected via resistor 16, to summing junction 37. Resistors 16 and 17 provide an input signal which is a constant which is utilized to represent a characteristic of a particular prime mover. This constant may vary between different prime movers. As well, the constant may vary in relation to the type of measurable variable of the physical system which provides other inputs.
Another measurable variable is supplied at terminal 41 Where this measurable variable represents a signal which is referred to ground potential. This signal may represent, for example, pressure of the physical system or the power generated by the prime mover or the like. Terminal 41 is connected to the input of amplifier 2 via variable resistor 21 and fixed resistor 22. The output of amplifier 2 is connected to the input thereof via feedback resistor 23. Resistors 22 and 23 are designed to produce a suitable loop gain of amplifier 2, for example 60, to operate upon the signal applied at terminal 41. However, inasmuch as the desired output signal of amplifier 2 is a function of other environmental conditions such as atmospheric pressure and the like, as well as the input signal at terminal 41, resistor 21 is inserted to provide variability in the amplifier loop gain. Typically, variable resistor 21 is set at the predetermined initial conditions and thereafter said resistor is used to adjust the gain of amplifier 2. As the system variable represented by resistor 21 is varied, resistor 21 is also varied to insert a larger resistance into the equation-representing amplifier 2 such that the gain thereof is decreased. The output of amplifier 2 is connected via resistor 24 to summing junction 37.
Summing junction 37 is connected to an input of amplifier 3. The feedback network connected around amplifier 3 includes resistor 18 and switch 20. In addition, depending upon the position of switch 20, the feedback network may be connected either directly or via resistor 19 to the output of amplifier 3. When amplifier 3 is connected to the feedback network as shown, the loop gain thereof is typically unity. However, in the event that the loop gain of 60 is too large for amplifier 2 and produce instability or other inaccuracy, amplifier 3 may be designed to have a loop gain of 2 while amplifier 2 has a loop gain of 30. In the feedback condition shown, the output signal Z of amplifier 3 is a function of the signals which are supplied to summing junction 37. If switch 20 is repositioned, to insert resistor 19 in the feedback circuit, the output signal Z is a function of the signals supplied at summing junction 37 modified by a factor represented by resistor 19. It should be noted that the factor represented by resistor 19 is correlated with the signal effect produced by resistor 21.
The signal Z produced by amplifier 3 is supplied to an input of the time division multiplier TDM 25. A suitable circuit for performing this function is shown in the copending application of W. H. Crowell, the instant inventor, entitled Time Division Multilier, bearing Ser. No. 675,596, filed Oct. 16, 1967 and assigned to the common assignee. In the referenced patent application, there is disclosed an arithmetic circuit which includes a plurality of operational amplifiers interconnected to operate upon an input signal in such a manner that, inter alia, a reciprocal function is provided. The time division multiplier described in the copending application is not a part of this invention, per se, but is a preferred means for supplying the reciprocal signal l/Z at the output thereof.
The output signal supplied by TDM is supplied via normally closed contacts KIA to the armature of switch 38. Depending upon the position of switch 38, the signal is supplied to the input of integrating amplifier 4 via resistor 27 either directly or via variable resistor 26. It should be noted that switches 38 and 20 are ganged and operate together. The switches are concurrently in the position shown. In the alternative, both switches are in the opposite position. Thus, it will be seen that when resistor 19 is connected in the feedback circuit of amplifier 3, resistor 26 is disconnected from the input circuit of amplifier 4. In other words, if the factor represented by resistance 19 is inserted into the signal Z, it is not necessary to insert it into the signal 1/Z. Conversely, if the signal Z does not include the resistance 19 factor, a corresponding similar factor is inserted into the 1/ Z signal by means of resistor 26.
The output of amplifier 4 is connected to the input thereof via integrating capacitor 28. The output of amplifier 4 is further connected to a counter driver 29. The output of counter driver 29 is supplied to a suitable counter 30 wherein a digital output is presented and/or displayed.
Thus, it is seen that amplifier 4 integrates the signal l/Z as a function of time and provides a suitable output signal. In a preferred embodiment, the time constant for the inegrator amplifier 4 may be on the order of hour or 6 minutes. On the other hand, the counter 30 may be designed to provide an indication which is related to hours. In this case, a decade counter or divider maybe inserted before the counter. Obviously, if the time constant of amplifier 4 is enlarged and the counting rate of counter 30 is reduced, the decade counter may be eliminated or, conversely, expanded to provide a greater number of counts if desired.
Thus, it is seen that this computer circuit operates upon at least four factors, two of which are representative of measurable variable of a physical system, one of which is a constant which is a function of the physical system and one of which is a function of its environment. These input signals are vectorially or algebracically summed to produce an output signal Z which is repreentative of the continuously computed, instantaneous useful life of the prime mover. The instantaneous life expectancy signal is converted into a rate of consumption signal which is integrated to produce a percentage or similar satisfactory output signal representative of the actual useful life consumption.
As an additional feature, the output signal produced by TDM 25 may be connected via resistor 34 to an input of amplifier 5. A variable resistor 32 is connected between a l5 volt source and ground. The variable tap of resistor 32 is connected via fixed resistor 33 to input 36 of amplifier 5. Thus, the low level setpoint signal provided at the variable tap of resistor 32 is subtracted from the output signal of TDM25 at the summing junc tion 36. Zener diode 35 is connected in a feedback path around amplifier 5. Specifically, the anode of Zener diode 35 is connected to summing junction 36 while the cathode of Zener diode 35 is connected to the output of amplifier 5 along with coil K1 which is referenced to ground. With this configuration, amplifier 5 operates as a comparator which produces a low level signal when the signal 1/ Z from TDM25 is greater than the low level set oint signal supplied via resistor 33. However, when the signal at summing junction 36 assumes a negative level, amplifier 5 produces a high level output signal which energizes coil K1. When coil K1 is energized, contacts KIA are opened and contacts KlB are closed. Thus, the input of amplifier 4 is connected to the variable tap of resistor 31 which is connected between a +15 volt source and ground, instead of to the output of TDM25. This connection has the effect of supplying a constant signal of a predetermined level to the input of amplifier 4 whereby the amplifier 4 continues to integrate this predetermined signal and produce an output at counter 30. In essence, this operation has the effect of continuing the calculation of the consumption of the operating life at a minimum level, even though the actual consumption level may be less than the minimum level. Thus, a certain safety factor is built into the system. In the event that the system is used as a billing or metering system, this has the efifect of establishing a base minimum billing rate regardless of relatively low utilization of the prime mover.
Thus, the preferred embodiment of an equivalent base load measuring system has been described. This system operates upon suitable measurable variables produced by the prime mover or other systems being monitored. It is clear that modifications of this system will be suggested to those skilled in the art. Any modifications of this system which fall within the inventive precepts supra, are meant to be included in this description.
The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
1. A computer for computing the equivalent base load hours of a prime mover comprising, in combination, first input means including means for deriving a signal representative of a first significant parameter determinative of said equivalent base load hours and including a first amplifier means for generating a first signal,
second input means to which signals representative of a second significant parameter determinative of said equivalent base load hours may be applied, second amplifier means, said second input means being connected for supplying signals to said second amplifier means for generating a second signal,
means for establishing a signal representative of the base load characteristic of said prime mover,
arithmetic means for algebraically adding said three recited signals to produce a composite signal which is a function of the equivalent base load of the prime mover, and integrating means connected to integrate a function of said composite signal to produce a signal representative of said equivalent base load hours of said prime mover.
2. The combination recited in claim 1 wherein said first input means includes temperature sensitive means, said temperature means being connected in the feedback path of said first amplifier means.
3. The combination recited in claim 1 'wherein said second input means includes compensating means, said compensating means providing adjustment for environmental conditions relative to a physical system related to said combination.
4. The combination recited in claim 1 wherein said arithmetic means includes a third, or summing amplifier for summing and weighting said three recited signals.
5. The combination recited in claim 4 wherein said arithmetic means includes means connected to the output of said summing amplifier for providing a signal representative of the reciprocal of the output signal of said summing amplifier, said integrating means being connected to integrate said reciprocal signal.
6. The combination received in claim 5 including comparator means connected to said arithmetic means, simulated input means, said comparator producing a control 6 signal as a function of the output signal produced by said arithmetic means, and switch means controlled by said control signal produced by said comparator means, said switch means selectively connecting said integrating means to said simulated input means or the output of said arithmetic means.
7. The invention set forth in claim 5 including the addition of digital output means for displaying an output signal.
8. The combination recited in claim 4 including compensating means connected in the feedback path of said third amplifier means to provide adjustment for environmental conditions relative to the prime mover.
References Cited UNITED STATES PATENTS 2,946,943 7/1960 Nye et al. 235--183 X 3,237,448 3/1966 Howell et a1 235183 X 3,250,901 5/1966 Brahm 235183 2,357,239 12/1967 Hohenberg 235183 X 3,362,217 1/1968 Evans et al 235-183 X EUGENE G. BOTZ, Primary Examiner F. D. GRUBER, Assistant Examiner US. Cl. X.R.