US1997476A - Compressor control system - Google Patents

Description

April 9,1935. F. o. WALLENE 1,997,476 COMPRESSOR CONTROL SYSTEM Filed March 26, 1932 INVENTOR 0. .Pl/ILLt/V:

ATTORNEY:

i Apr, 9,1935 v l I i f 1 I v UNITED STATES PATENT 1 OFFICE v 1,997,476 1 comanssoa oormtor. SYSTEM Frank 0. Wallenc, Lakewood, on Application March 26, 1932, Serial No. 601,393

4 Claims. (01. 230-21) This invention relates to method and apparatus mining in' the chamber and its pocket at the end a for automatically controlling, for any desirable of the piston troke, such remaining gas expandreason, the amount of compression work done by ing to assist the piston to return, and thereby rea gas compressor, such as for economy in conducing the work performed on each stroke. By 5 struction, design or operation of the compressor automatically controlling or adjusting the volume 5 itself, or of the plant or system of which it forms of the clearance pocket or pockets, and by maka part, or for maintaining desirable conditions, ing the adjustment sensitive to a suitable or de- Such as a constant compressor discharge or suosirable factor of operation of the compressor or tion pressure, or forany other reason. plant equipment supplied thereby, it is possible One object o! the invention is to provide-imto produce or maintain certain desirable condi- 10 proved method and apparatus of the character tions. While the invention may be applied for described, in which compressor control is secured use in a variety of ways, some of which will be deby automatic adjustment or control of adjustable scribed, it will be understood that it is not limited clearance pockets in step with or according to to these particular instances but is capable of variations in some suitable or desirable 'controlsome variation within the scope of the a p- 1 ling factor. r pended hereto. More particularly, as applied to refrigeration, Speaking first with reference to its application an object of the invention is to provide an imin the refrigerating art, it is-possible to use the Proved gas compressor system sensitive to some invention in at least twoi if not moreways. It may pressure value at the compressor, such as the be taken advantage of to produce inherent 66011- suction pressure, and also to the flow of energy y of Operation of e compressor. t p to the driver thereior, either for securing greater eu rly w n h r q i d w r n ad of t economy in operation or for avoiding peak loads plant V i v r a v n p i Of ope iom in'the energy supply, as will more'tully appear, as during the day. Again, where the power source Further objects and advantages of the inve comes from outside the plant, such as electrical 25 tion will in partbe obvious and in part will apcurrent p c as d om a power compa y, it may pear more clearlyhereatter. I be desirable to avoid unduly high peak load be- In the drawing, the view is a diagram, partly cause of the influence of peak load upon current in section, illustrating one embodime t f th cost. Insuch cases, the present invention is'taken invention. advantage of to avoid the use of an excess quan- 30 According tomodern practice, gas compressors y of p c a d p w r r t e pu pose of k pare usually driven by constant speed driv ing the peak load within the desired maximum either a constant speed electric motor or, in some limit- I cases, by a steam turbine operating most eflicient- While the invention is capable of use on double as 1y at a definite speed which desirably does not a i or u t -st p ess rs by pr vid n materially vary. with such drivers therefore, it eans for control of a part or all of the clearis not possible or at least not conveniently possio ce pockets either simultaneously or in suitable 'ble, to vary the amount of compression work done 118111110113 With each 011116131 have illustrated for by'the compressor by changing the speed of the convenience the application of the invention to 40 driver, for which reason I resort to adjustment 2. single a n Compressor h m r 0f 4 v of a clearance pocket for the same purpose, and which communicates y y Of an inlet Valve 3 for purposes of illustration, assuming a compresw the S o 0 S pp y p p and y Way sor driven by a constant speed electric motor, I of an outlet valve 5 with the discharge pipe 6. cause' the adjustment or the clearance pocket to The piston I is actuated by an electric motor 8 be sensitive to both the amount of electrical which may be u ed o be a constantspeed 45 energy required for compressoroperation and to electric motor and which is supplied by current the pressure of the 'gas handled by the vcomthrough the leads 9 from the main line source pressor. of current supply It). The present invention, generally speaking, is Chamber'2 communicates by way of an opentherefore based upon the well recognized ability ing II with the adjustableclearance pocket 12, 50 to control the amount of compressor work done which lies within a housing l3 attached. to the e by a gas compressor, by providing it with adjustcompressor cylinder, one wall of the clearance able clearance pockets by means of which it is pocket being formed by a piston ll adjustable to possible to vary the effective volume of the'cyland fro in any suitable manner, or by any suitinder chamber and consequently of theses reable mechanism, operated hydraulically, elec- 55 trically, or from any source of power, and shown as operated by providing it with anon-rotatable strumentalities for the purpose of securing control sensitive to the pressure of the gas: at the compressor, either suction orv discharge, as may be desirable or necessary, and also sensitive to the power input to the compressor driver. For illustration, and not in any sense of limitation,

' I have shown the control system as comprising two instruments, marked respectively A and B, the first of which is sensitive to the electrical energy input to the compressor driver 8 and the second of which is sensitive to the compressor pressure, the two instruments conjointly controlling operation of the clearance pocket adjust- I ing motor 58.

v lar to a polyphase or single phase meter. For a.

Electrical instmment A of course is of a char-- acter suitable to the kind of current required for motor 8. For an [1.0. system, it will be simi- D, 0. system it may be similar to a D. C. watt meter. in the arrangement shown, which supplies alternating current to motor 8, instrument A includes'a disc 2% carrying an arm 2i and influenced by coils 22, 23 supplied by current transformers it, 25 associated with leads from the supply line to motor 8, and also sensitive to potential coils'zu, 2i suitably connected to the line. The torque developed by the disc 2c is proportional to the amount of power taken from the supply leads by motor a and is balanced against an adjustable loading spring 2%.,

Instrument'E includesa pipe 293 communicating with the compressor so as to beresponsive to its pressure, and in the instance shown come municating with the suction side of the coinpressor; jsaid pipe also communicates with a bellows 30, the movable part of which actuates a rack '38 operating alpinion 32 with which rotates an oscidating arm 33, the bellows pressure being balanced against the usual adjustable loading spring 33a.

Arm 2| of instrument A is connected by a link 34 to arm 35 pivoted at 36 and carrying a double e'ndedcontact member 3! cooperating with two adjustable contacts 38 39 on the arms of a yoke carried by a lever 40 also pivoted at 36 and working between adjustable 'limitstops 4i and connected by link 42 to be operated by arm -33.

The centercontact is connected by a wire 31a to the center onset the supply leads, while the contacts 38, 39 are connected-through coils G3,

44 to one of the other leads, for'actuating the reversing switch marked generally 45. These two coils 43, 44, separately actuate the switch parts 45a, 451), which connect the motor ill to the main leads I, so as to cause rotation of said motor in one direction or the other according to which switch part is closed, and to thereby either increase or decrease the volume of the clearance pocket or pockets, as may be required by the control operation in progress.

Let it be assumed that 46 representsany refrigerating system or apparatus supplied with refrigerant bythe compressor through its discharge line 6, the refrigerant returning to the compressor as a gas byway of the suction line 4.

Gas enters the compressor cylinder through valve 3 as the piston moves to the right. As it completes its stroke and returns, valve 3 closes and gas escapes through valve to the discharge line 6 when the pressure in the cylinder rises slightly above that in the discharge line. A certain amount of gas has been trapped-in clearance pocket [2 and such other'clearance space as is necessary for mechanical reasons between the piston and cylinder head. As piston 1 starts to return, the gas in the clearance space, including pocket l2, expands to a pressure slightly beand fills the cylinder'during the suction stroke 0 to a pressure nearly equal tothat in the suction line I.

If piston I t has been so adjusted that it lies in a position to close the opening 8 i between the clearance pocket and the compressor cylinder, it is obvious thatwhen piston 1 starts its suction stroke there will only be a small amount of clearance gas, andonly a small movement of piston l is required to bring the clearance gas pressure down to a pressure below that in pipe l, resulting in valve 3 opening much sooner than when the volume of clearance space is greater, or, in other words, when piston it has been adjusted'to a position such as shown in the drawing. It is obvious therefore that the amount of work done by low that in pipe 4, whereupon valve 3 again opens the piston i can be varied considerably by an irigerating system constitutes anappreciable pcrtion, say 50%-to 75% of the total power demand of the plant as a whole, and that 100 kw. has been determined as the maximum power demand per missible, because if the peak load is permitted to go beyond that value thecostof electric current becomes excessive. It is therefore desirable to keep the total current consumption in the plant.

below 100 kw.

Let it be further assumed that the total plant load, for some reasonv such as an increase of energy demand by the equipment 48, tends to increase the load to 101 kw., the effect of this increasebeing to cause rotation of disc 20 and closing of contacts 31. 39. As a result coil 44 is energized, closing the switch-15b and causing. motor I 8 to rotate to increase the clearance space It by moving the piston M to the left. This instantlyproduces a decrease in the amount of power required by motor 8 and therefore in the currentjtaken from the leads I, reducing the torque appliedto the disc 20, with the result of openingthe contactsil, 38,and motor i8 stops.

The'gas pressure in the pipe 4 is not likely to change very quickly. In fact, under usual plant conditions it may require an hour ormore before there is anoticeable change, because the lag in the effect-through the refrigerating apparatus is quite material. However; the controlling system has instantly reduced the power demand and keeps it within the required maximum.

Suppose that current demand recedesto 99 kw.

and that tension of spring 28 is such that the disc 20 therefore rotates to the left, closing contacts 31, 38. Coil 43 is now energized, closing the switch 45:: and causing motor IE to rotate in the opposite direction and thereby decreasing the clearance space, which in the same manner causes the motor 8 to take more power, resulting in an increase in the torque'in disc 20, which again opens contacts 31,18, so that the motor It stops. The parts of the controlling mechanism, that -is to say, of the instruments A, B, are so formed,

such as by the spacing of the yoke arms of lever 40, and are so adjusted, such as by adjustment of the stops 4 I, of the tension of the springs 28, 34, and of the location of the adjustable contacts 31, 38,39, as to absolutely prevent the current input to the plant as a-whole exceeding the desired maximum, 100 kw. in the instance under consideration, and at the same time are so formed and adjusted as to insure that at least sufllcient current is used to operate the compressor up to its maximum capacity within the limits of the maximumcurrent peak. when an electrical demand, by the plant as a whole, tends toexceed the desired maximum at a time when additional refrigeration isalso required, it is obvious that such additional refrigeration will not be immediately provided but the efiect of the demand therefor will be retained in the controlling system so that when the electrical demand of the plant as a whole later drops to' a value within the maximum permissible amount, the duty of supplying the necessary extra refrigeration is sumed and satisfied.

The invention, however, isnot limited to use for the purpose of limiting them'aximum electrical input to the-plant as a whole, but may be applied immediately asfor use in securingreasonably constant suction pressure and thus securing economy in the operation of the compressor itself. In such an arrangement, for example, the instrument B may be subject to the intake pressureto the ccmpressorand instrument A maybe subject to the current supply leads to the compressor driveronly, and the control parts are formed and adjusted as described, so that the current input is limited to that amount which will properly operate the compressor at the desired capacity. -'If at'any time while so operating there is a demand for additional refrigeration, the effect of such demand again will be retained in the control system so that the additional refrigeration can be supplied when the refrigerating load-is later reduced. Such an arrangement is useful where the refrigerating load varies materially. during the'day, being heavierat night,

forexample, than in the day time or vice versa.

.Theinvention mayals'olbe applied ior'use in,

the operation of compressors for other fluids,

such as an air compressor, where. it may be desirable to maintain a given discharge pressure but nevertheless prevent the power input to the ment A :to the current input to the compressor.

described,'as well as others to.

compressor driver from exceeding a given maximum. Here instrument 3' is made subject to the compressor discharge pressure and instru- In all instances 'whichthe invention be applied, it has the advantages of'providinsa graduated. imiformly varying or' modulated adjustment of the compressor load by graduated adjustment of clearance volume. the system mnction ingmoreorlessasan automatic governor. The

clearance pock' et'adim t uc -8mm!!- 3 a An I the driver for or its equivalent, works back and forth, first mcreasing and then diminishing the clearance always with a tendency to come to rest at the desired position as soon as possible. 'As a consequence, the entire system tends to maintain the most eiflcient operating conditions, as well as. securing the necessary limitation of power input within any desired maximum value to avoid ex- "cessive peak loads, as will be readily understood.

To'accomplish this'commercially; in some cases, such as in a refrigerating plant, it may benecessary to utilize a brine storage or heat accumulator,- as it may be termed, for the purposeoiabsorbing heat during the peak loads when the gas compression work is done at areduced rate.

pocket volume in accordance with conditions, but

Other advantages and uses of the invention art.

What I claim is: K

'1. In combination, a compressor, a power operated driver therefor, said compressor having an adjustable clearance pocket, and means sensi-. tive to variations in the intake pressure atv the compressor and to variations in the power input will readily be apparent to-those skilled in the to the driver for gradually adjusting the clear- I ance pocket.

2. In combination, a pressure'utilizing system,

a compressor arranged to supply pressure to said system, a power operated driver for said com-v pressor, said compressor having an adjustable clearance pocket, and means sensitive to"variations in the intake pressure at the compressor and to variations in the power input to the driver therefor for gradually adjusting the 'clearance pocket. k

3. In combination, a pressure utilizingsystem, a compressor in, circulatory communication therewith and thereby\ arranged to supply pr sure to said system, said system being of such character that variation in the intake pressure of said compressor is delayed following variation in compressor output, a power operated driver for said compresso means for adjusting the clearance space of said compresso and means for controlling said last named means, said controlling means being sensitive to M8? tions in the intake pressure. of said compressorv and being adapted to maintain a predetermined power input to'saiddriverr 4.1n, combination, "a pressure utilising system, a compressor in circulatory communica tion therewith andthereby arranged to supply I.

pressure to said system, said s'ystembeing of such inherent character pressure oi said compressor-cannot promptly foithat variation in the intake l'lowyariation incompressoroutput, a power op erated driver for said compressor, means for ad-f clearancespace of said compressor. I hereby increased clearance. space to decreased, output of said compressor and to said controller havins. another

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