Document bynZJeo6jZvVbEqkjOxDrgzyy

UNATTENDED PUNT TBS*" AUTOMATIC INDICATINO system is divided to certain group of on trouble. Another control group (hull down but one mochtno. instrument* ond controls will immediately shut down the plont Both control groups will send on indication to the ADT office KIECTRICAI DISTRIBUTION within the plont stems from the into the moln 440-v oc bus, Excitation' for the synchronous 27-kv feeder from local utility compony. All motors are topped motors comes from separate mg set. Reloy indlcotes o dc failure Compressors Are Powered by Unity-Power-Factor Synchronous Motors... ...Totaling 960 Hp Lockinc thk door on 1,750,000 cu It of refrigerated spoce for 16 or more hours el t stretch colls lor o Hependoble troublo-indicnting oyslcm . . . one that shut! down one or more machines, if need be, plus sending a signal |o a cen tral office. The signal, in our cose, is sent to a local office of the American District Telegraph. Circuits ore like those for fire-alarm protection. Our plant lias a total refrigerating capacity of about 27S lone; 175 tons .for storage purposes through o brine cooling ayoiem; remainder serves blastfreexer rooms. Blast-freezer capacity is 100,000 lb of produce for 24 hr at -30 F. Btssl freezer .operates through direct-expansion ammonia system. Refrigeration equipment o e n t e r s about nine 6-cylinder 720-rpm 2-stoge compressors. They represent a total of 960 hp, synchronous motor'. Consider the refrigeration system bo operating two loads; brine-cooled storage rooms ond dircet-exponsion blast freezers. Of the nine compressors in tho plont, six handle the first stage, while three are In the second. Piping is to arranged that any of the low-stage units con be run on brine suction or blast freezing. Each compressor Is well protected from ac cidental damage as indicated in above ketch. Brine circulated through a fin-pipe system is cooled by multi-pass brine coolers connected to an ammonia ac cumulator. Banks of fin coils pick up heat, transmit it to the circulating brine. Accumulated frost is removed by circu lating hot brine through the system. Compressed ammonia gss, as It is dis charged from the high-stage machines, is piped to a bank of six evopnrative condensers on the plant roof. Clecfrlcol system Is spread about o nucleus of nine synchronous motors. They power the refrigeration compres sors. Six of the nine are'60-hp motor' thol drive the low-stage reciprocating compressors. These units serve for the blast freecing operation or brine cool ing for storage area*. They operate at suction temperatures to -40 F. IJk'*wise, the three remainlng high-stoge re ciprocating compressors are each driven by a 200-hp synchronous motor. Here an mg act is used to supply the common dc bus. fn our case motors were picked that will operate normally si unity pf. '' Keep in mind, however, that some synchronous motors are designed to run st a leading power foctor. This is im portant where much of .the remaining load is Induction motors,' drawing a siz able chunk of wattless power. Size and number ol leading pf synchronous mo tors osed hinges on amount of reoetive kva needed to balance out effects of in ductive equipment. This consideration did not come into the picture for usOur major power loading consists of . synchronous motors; there is little lag ging reactive power to account for. All synchronous motor control* are low-voltage fuse type. They ore equipped with disconnect time-lag fuse* permitting full-voltage starting. A pol arised field frequency synch ronoii*-nu>tor control system is used throughout. The local utility company supplies all electrical power. After passing through' n 27-kv to 440-v atepdown transformer, the underground electrical feed is run through a 2000-amp service. Our main ac bus is at 440 v. Each of the syn chronous motors feed off ihb bus. Excitation for the synchronous melon . - is supplied by an mg set, whoso moior is tapped into the main station bus. Generator of this rag set feeds a dc bus which, in turn, delivers dc excitation power to each synchronous motor. Romoia Indication. As indicated .above, the remote signaling syotem we adopted Is a companion to the conven tional protective system as far as wiring and operation go. It simply means using another elrcuit to the ADT office. A signal is transmitted to tho ADT office if there's s significant mechonical or electrical failure, or if an abnormal temperature or pressure is reached. When the signal it received in the cen tral office, the ADT telephones the opersling engineer st his home. If he cannot he reached, a local refrigeration service organisation, previously selected, is called. Tho operating engineer or re frigeration serviceman then drives in the plant, locates the trouble, and pul* the machine back in operotion. Controls that shut down equipment ore bUo wired to indicotSng lights in the plant. When trouble pops, these lights on and remain lit till reset by the mtB ohootmg trouble. They serve at 1s **5 3 5 &1 1 ZL rrttitr 9 V Cooltr 3 Coottr 2 ,Wc ,>. ft fi-ftafinZ,.: Trtttir 4 rrttitr e rrttitr S Frrtitr T - Ctr 1 E& v;. Trvtku>p p/gtterm ' | cart ....... : ' /'n uv '. BJtaS t I rrttitr XX ' IT7" sit;-; REFRIGERATION IOAD is supplied by 173 tons brine-cooling refrlgerotkm wOrVIng In 2-stoge system. There ore 100 tons ol relrlgerotlon ot -30 F for blest freezing a tip-off to aim trouble source (or the person answering the ADT call. In this woy he can quickly tell which control device caused the shutdown. System was designed by the author and I1 I) Christenson, formerly with the Merchants Refrigeration Co, in consul tation with J Holbrook of Beldeh-Porter Co and V Alexander, L Hanson, A Heintz of live Carrier Corp. 97 ENGINEERING AND MANAGEMENT SECTION JANUARY )93) I ENGINEERING AND MANAGEMENT SECTION 9)