Purdue University Purdue e-pubs nternational Compressor Engineering Conference School of Mechanical Engineering 1984 An Application of TRAC to Capacitor Motor for Hermetic Compressor K. Nakane Y. Tozaki H. Sakamoto Follow this and additional works at: http://docs.lib.purdue.edu/icec Nakane, K.; Tozaki, Y.; and Sakamoto, H., "An Application of TRAC to Capacitor Motor for Hermetic Compressor" (1984). nternational Compressor Engineering Conference. Paper 449. http://docs.lib.purdue.edu/icec/449 This document has been made available through Purdue e-pubs, a service of the Purdue University Libraries. Please contact epubs@purdue.edu for additional information. Complete proceedings may be acquired in print and on CD-ROM directly from the Ray W. Herrick Laboratories at https://engineering.purdue.edu/ Herrick/Events/orderlit.html
AN APPLCA'l'ON OF 'l'rac TO CAPAC'l'OR 1-1'l'OR FOR lll~rt~c'ric COMPRSSO!l Ka.zuhiro Nakane, Yasuhiro To?.nki,. lirota.ka Sakamoto Shizuoka. Worlw, Mitsubishi Electri.c Corporation Shizuoka City, Ja.pan ABSTRACT This paper refers to a.n n.pplication study of 'l'luac to PSC motor for thft hermetic compessor. t is 1-1ell lcnown that 'l'hac rlel nys pharja ane,le of the current and has no losses if it is consider(\ as ideal flwitch. 'l'herefore it is possible to c;et a ldncl. of variable capacitor ljy connecting ~'HAC Nith capacitor in series antl controlline; the firing angle of it. 2 poles,single phase induction motor shown in Fie;. l was used for our experiment. its voltage,frequoncy and output rati.ngo are 1 V,5/6 J!v. and 1 11. t is a. 1mi 1 t-in motor for the rotary type hermetic compressor shown in Ji'ie;. 2. 'l'hore are three types of the wirings of the starting device for thifl motor,as shown i.n lcig, 3. A shows CSR moto:r,n shows P'l'C asoist CSR motor and C sho~1s PTC nssist PSC motor. The customer is able to choono a most suitable type of them for use. By use of this vari.able capa.ci.tor for PSC motor,\ 11:> could obtain the performance similar to CSR motor. Therefore ~1e bel iove that this type motor should be developed as one of the single phase motor for the hermetic compressor with the progress of the electronics. JN'rRODUC''ON Various kinds of single phase induction motors such as PSC,CSR,CSR,RSR,PTC assist PSC and PTC assist CSR are used for hermetic compressors. 1-1e choice one of these according to the purpose for use. n recent years,it is prosperous to tr,y the application studies of semiconductors to the sphere of the motor control. An application study of TRAC to a single phase induction motor is one of these. As explainning in this paper,it is possible to cet a ki.nd of varialjle capacitor 1Jy connecti.ng 'l'rac in series with capacitor of PSC motor a.nd controlline; the firing angle of it. We call this type motor TRAC assist PSC motor in this paper. This paper refers to the torque characteristic of 'l'rac aasist PSG motor and the starting performance on the actual hermetic compressor,based on the experimental results. And we try to compare it with the other existing motors. n addition, we view a possibility of TRAC assist PSC motor for hermetic compressors. Fig.1 1 W motor used for test TEST MOTOR ANT CONTROL DEVCE OF 'l'rac Fig.2 Rotary type hermetic compressor 168
A: CSR motor B: FTC assist CSR motor l 1: Main winding z: Auxiliary \>tin ding 3: Relay 4: Starting capacitor 5: Discharging resistor 6: Running 7: P'l'C capaiitor thermistor Fir;. 5 shows the control device of TRAC made for our ~xpcriment. Fir;. 6 shows its block diae;rnm, and Fir;. 7 shows its time charts. t is possible to set 11p the firinr; o.n(\le of 'l'rac ljy. l. mace., uain~ thjs cotrol device. The detection circujt for the au:x:uiar;v Hinrlinr; val tar,e operates to turn TRAC into no fire. For this operation, we make usc of the property which the auxiliary Hi.ndinr; voltsr;e increases with revolution in PSC motor,as ~hown in Fig. B. And the relation between the auxil iar;v winding voltnr;e nncl the oper;j.tinr; point of the detection circuit has a hysterisis characteristic as shown in Fig. B. 1 C: FTC assist PSG motor Fig. 3 Wiring diagrams of the hermetic compressor motors for refrigerator Fig. 5 Control device of TRAC Fir;. L1 sho~rs the Wl-rl-ng diae;ram of TRAC assiot PSC motor described in this paper. TRAC is connected in series with capacitor of PSC motor. Heoti fioation ht tenation Voltage comparator TRJ\C J \ R \. unn1ng Main \.---winding Auxiliary winding capacitor D A: To main 1nd1ng B: ~ o running c pacitor C: To auxiliary winoint D: To common Fig.!1 Wiring_diagram of TRAC assist PSG motor Fig. 6 Block diagram of the control device 169
Source voltage ~~~vvv \J'C lr lr Aux. winding! V 1 A 11 (\ (\ (\ /'\ A 1\ voltase 1 r 11,,v V V V~\..J\, ditector Zero Counters Latches, -tion ll,, 1, 1,1 lr 1 1 1../ v~f :evel "' Recti fica-:.:=:~;;~=:::::::::::::::::=:;:===::=::::: Attenation Vol tase comparator Control Drivers logic _ul...-jl..-l-...l.-j._...l.-j v v V\/\: [l [\ An 1\1\1\ ------- Time Fig. 7 Time chart of control device Firing angle H nl..- {;h "!il :.> = o<> Firing angle = 18" ---... Time Fig. 9 Definition of the firing angle Fig. 8 Speed Fire No fire llustrating the relationship between speed-torque. aux. voltage curves and fire of TRAC TORQUE C!ARACTERRSTC OF TRAC ASSST PSC MOTOR... bo. ~.. 3 '-' bo <11 r-l S... <11..- ii'o!! 6. 9 Fig. 1 i.5 Slip Main winding current d llustrating the phase angle relationship between main winding current and aux. winding current (Base is source voltage) correspo~ding to slip,for PSG motor We define the firing angle of TRAC as shown in Fig, 9 in this paper, i.e.,?:ero riee,ree of the firing angle corresponds to zero d.egree of the source voltage. Ji'ir,. 1 shows the phase angle of the main winding and auxiliary winding currents for PSC motor used for our experiment,which the source voltage is base. Generally,the main winding current lags the source voltage,and the auxiliary 1~inding current leads the source voltage. ' '!'here fore, in case that the firing angle of TRAC is zero degree, the auxiliary l linding current is chopped by angular lead for the source voltage. Fie,-. 11 sho~1s the measured waveforms of the source vol~ege (E 1 ) and the auxiliary winding current ( ) corresponding to the firing angle of " 1 47-5 a and 7 3.4 s,t slip~l (at starting) for TRAC assist PSC mo tor. As seen from this figure,the phase ' angle of lags as the firing engle of TRAC a. increases. That is to say,it shows the characte;- ristic of a kind of variable inductance. " 17
1 2 3 Speed (r.p.m.) Fig. 12 Measured speed-torque curve for TRAC assist PSC motor Firing angle =73.W The relation between the starting torque and the firinb' angle of TRAC is sho\m in Fig. 13, These values of the starting torque were obtained from above measured speed-torque' ourves. As seen from this figure,the maximum point of the starting torq1.1e is given at the firing angle of nearly 5 degrees. ts value is about 3 3 times as much as the starting torque of PSC motor,which i's shown as broken line'in Fig. 13. And in this figure,the sta.rting torque equals zero at the firing angle of nearly 115 degrees. t means sino<... in the equation (1), i.e.the phase difference between the Fig. 11 Measured aux. winding current tif TBAC assist PSC motor (slip=l) Starting torque of PSC motor is exp~essed as the follo~ting equation,as well known. (1) where r Main winding current m. as Auxiliary windine; current (1 Phase difference between and T 6 s Sta~ting torque m a Therefore it ie possible to control Ts by control 1 oo - ---- - - - --- _qo- ~Starting torque of PSC ling asin ~, i.e.,by controlling the fi~ing angle of TRAC for TRAC assist PSC motor. Fig. 12 shows the measured motor speed-torque curves for TRAC assist PSC moto~,correepondine; to each firing angle shown in Fig. 11. They are measured f~om firing angle of degree to 14 degrees. t is apparent that the speed-torque curve changes as the fir).ng angle of TRAC changes b 3b 6b 9b Firing angle (degree) 1 1~ Fig. 13 Relation between measured starting torque and firing, angle for 'rrac assist PSG motor 171
main winding current and auxiliary winding current becomes zero degree at this firing angle. ncreasing more than this firing angle 1 the-auxiliary l'linding current lags the main tlinding current 1 i.e, sj_no(<o; T < in'the equation (1). t. B means the motor rotates in reverse. Fig. 14 shows the relation between the break-down torque and the firing angle of 'l'rac. These values of' the break-dolm torque Here obtained from above measured speert-torque curves in the same manner as the stfl.rting torcj_ne. As aeon from this figure,tho maximum point of tho break-down torq\te is Bi von at the firing angle of nearly 55 degrees. ts value ierabout 1.4 times as much as the break-down 7 Fig. 14 3 6 9 12 Firing angle (degree) Relation between measured break-down torque and firing angle for TRAC assist PSC.motor torque of PSC motor,whioh is shown as broken line in Firr. 14. Pig. 15 sho1-1s the rela.tj on between the starting ~.nd llreak-down torque and the firing angle of 'l'fi.ac. 'l'he values of the torques are expressed a.s ratio,~lhich is 1 in case of PSG motor. 'l'he pointe of the maximum startinr.; and break-down torque corresponding to the firing angle of 'rrac shift a :fel l. And the starting torque is high ratio more -blum -the break-c-lown torque. U) p,.jj 4 U) rl UlO ]1----~~~~r-,--,--,,--,--.--T--r--rj--rl -,r-,- ~~3- ~ H p:; 2 E---1 r-t.jj m H QJ ;:J o H 8 1- -1, oo.. oooo oo Oo oo. Starting oo :>. A J:>.J:>.:>. A;A:>.:>.AA:>.~:>.AA~~O torque 3 6 9 12 F'ig. 15 Firing angle (degree) Relation between the starting a~d break-down torque ratio (PSC=l) and firing angle for.trag assist PSG motor El ~~~~~~~~~~~~ Ea~Wi~~~~hF~+f~~~t,+~~Hw.~ft~~~~~~~~~~~~f~=~-l~~.;~:~.! ~~i~-~~~u~~~~~~~,,~:~ 11 -~:..r:'l... r\:.l msec. E 1 ; Source voltage Ea; Auxiliary winding voltage Fig. 16 Starting test data of TRAC assist PSC motor on the actual hermetic compressor A 1 i Common line current ai Auxiliary winding current Main winding current m' 172
STAUTTW PERFORMANCE ON THE AC''UAL HERMETC COMPRESSOR Fig. 16 shows the electrical performance data of TRAC assist PSC motor from start to full speed on the actual hermetic comprssor shown in Fig. 2. t shows the case that the firing angle of TRAC is setted up at 5 degrees,whi.ch we can ge.t the maximum value of the starting torque. From a practical point of view,we need set up the firing angle to take into cosideration of the starting, break-down or transient accerated torques cooperated with the loadine torque in the system. TRAC is turned. into no fire at the point A shown in Fig. 16. At this point,the detection circuit foi: the auxiliary winding voltage of the control device shown in Fig. 5 operate,and the motor changes to the condition of PSC. CDr1PARSON OF TRAC ASSST PSC MOTOR WTH TilE EXSTNG OTHER MOTORS We make the performance comparison of TRAC assist PSC motor with the existing other motors using the experimental results obtained by changing the electric parts except for the running capacitor of the motor shown in Fig. 1. 7 6 1 CSR.. (PTC:~ ;~. PTC assia~ o--\-- -1-t'- -- /7' ~ P'rC=15& ~~,;._.-7,-- i PTC assist CSR, / (P'l'C=33n) PTC=33.Q. -< H H +' +' +' o..-.. o o s. s a Olf\U o:n -1 ~ o:n o:n p., <ll p.. p....-l +' b.o +' Ul 1'1 Ul rl C\l rl Ul Ul Ul b.o Ul C\li:: (1j rl u -< ~-rl 8 H">-< p.. P<--- 8 2 ho 6 8 Starting capacitor (tjf) PTC assist CSR motor CSR motor Fig. 17 Measured starting torque comparison of TRAC assist PSC motor with the other motors Starting torgue Fig. 17 shows the starting torque of TRAC assist PSC motor at the firing angle of 5 degrees, together with the existing other motors. As seen from this figure,trac assist PSC motor at the firj.ng angle of 5 degrees, and CSR and PTG assist CSR motors having nearly 3 1-' F starting capaoi tor have a nearly eq_ual value of the starting torque. And the starting torque of TRAC assist PSC motor is nearly 1. 3 times value as that of PTC assist PSG motor having 15 n PTG,and nearly 1.4 times V!l.lttc as that of PTC aesist PSC motor having 33 g PTC. Ereak-down torgue Fig. 18 shows the break-down torque of TRAC assiet PSC motor at the firing angle of 55 degrees,tcgether with the existing other motors. As seen from this figure,trac assist PSC motor at the firing angle of 55 degrees and GSR and PTC assist CSR m~tors having nearly 2 1-l F starting capacitor have vnearly eq,ual value of the break-down torque. And the breal<-down torque of 'l'rag asai.st PSG motor is nearly 1.8 times value as that of PTC assist PSG motor having 15n PTC,and nearly 1.5 times value as that of FTC assist PSG motor having 33 n PTG. aloo flo Ql ;:j " -t.. 5 +'., 7J <ll J1 CSR PTC assist c~ko (P'rC:l5Q) ~ t.---a /"". o-------~~ ~-- PTC=33.o. o \ PTC:assist CSR ~ (PTC=33Q) t PTC:l5.o ~ 1- H H 2 4 6 8 o--. +> +> +' Starting capacitor Olf\ Slf\ a a (pf) ~ Jl' u u PTC assist CSR motor o:n o:n p., QJ p.. p.. rl +'b.o +' -~ ffi 1/J rl Ul Ul Ultto Ul C\'51'1 <U rl Ul-< t.) ~~ 8 p:;.,_. 8 p.. asrr motor Fig. 18 Measured break-down torque comparison of TRAC assist PSC motor with the other motors 173
VEW N FU'rURE OF TRAC ASSST PSC MOTOR FOR THE HERMETC COMPRESSOR for restartin~,different FTC assist CSR motor. from PTC assist PSC or 'l'1>ble 1 shows the coat comparison of the electric parts for various types of mot~ under nearly same value oondi tion of the atartine; torque. As seen from this table,trac assist PSC motor is not the best one of the minimum cost for performance. ) A B c D ~ Starting capacitor. Running 27 capacitor 16 -.e--- v v -...,..._ ~ V V L Relay 55 Discharg- 1/ V ing 2 resistor ~ V -- PTC 26 L TRAC..R V 1/ V Control 125 device Total <::oat Table 1 1 69 53 152 J\: CSR Numerical value : B: Ratio PTC assist CSR C: (Total cost P'l'C assist PSC D: of A=lOO) TRAC assist PSC Cost comparison of the electric parts for various types of motors (under nealy same condition of the starting torque) lut the existing motors have some technical problems to be solved. For example,csr motor has a meohanical relay to break the circui-t of the starting capacitor,therefore it has the problem of a noise with on-off 1 which is a.n unavoidable problem. And although P'rc assist CSR motor achieves the purpose to do away the mechanical relay,it has a fault that the motor is not able to be restarted immediately. Decause PTC is required the time for cooling to be a initial registanoe after the power supply was turned off. And FTC assist PSC motor has a same fault as PTC assist CSR motor 1 in add.ition,ita value of the starting torque is insufficient in comparison with other motors. TRAC assist PSC motor has some superior ohracteristics comparing with these existing motors. For exa.mple 1 the mechanical relay is not necessary, therefore it has not the problem of a noise. n addition,it is possible to get the starting torque As there is a possibility of cost dohn for the control device by the mass production or the integration 1 it is enough to say that TRAC assist FSC motor has a possibility of a practical use i~ future. CONCLUTON t is possible to control the motor torque by connecting ''RAC in series ~1i th oapaci tor of FSC motor and controlling the firing angle of it. We obtained the following experimental results in 1 W motor for the hermetic compressor. (1) The value of the maximum starting torque of TRAC assist FSC motor is about 3-3 till)es as much as the starting torque of PSC motor,and s.bout 1. 3 times as much as the starting torque of PTC assiot P3C motor having 15u PTC,and about 1.<1 ti.mes as much as the starting torque of P'rc aesist FSC motor having 33 n FTC. And it is corresponding to CSR or PTC assist CSR motor having nearly 3j~F starting capacitor. (2) The value of the maximum brealt-down torque of TRAC assist FSC motor is about 1.4 times as much as the break-down torque of PSC motor,and about 1.8 times as much as the break-down torque of PTC assist PSC motor having 15 Sl FTC,and about 1.5 times as much s.s the break-down tortjue of P'rC assist FSC motor having 33 n PTC And it is corresponding to CSR or PTC assist CSR motor having nearly 2 ~ F starting capacitor. (3) The maximum point of starting torque is given at tho firing angle of nearly 5 degrees,and that of break-dotm torque is given at 55 der;rees. They shift a little with each other. TRAC assist FSC motor has some superior characte~ ristios comparing with the other existing motors. Although ue cannot to say that it has a sufficient practical use with the present cost level,it should be developed as one.of the single phase motor for the hermetic compressor \~i th the progress of the electronics. We reported as for the application of TRAC to existina PSC motor in this paper. After this it is necessary for us to investigate to make the motor design most suitable for THAC assist PSC motor, and tre shall continue to study. REFTJTENCES (1) S. 11aki, "Characteristics of condenser motor controlled by antiparallel connected thyristors" 1 'J'he.iournal of the Electric Society of Japan, 1978 (2) Y. Yoshida, M. Tria, S. Ozaki 1 "On the variable torque characteristics of capacitor motor drive by 'l'rac", The "journal of the ' Electric Society of Japan, 1983 174