PLC是以微處理器為基礎，綜合了計算機技術、自動控制技術和通信技術，用面向控制過程面向用戶的“自然語言”編程，適應工業(yè)環(huán)境，簡單易懂、操作方便、可靠性高的新一代通用工業(yè)控制裝置。PLC是在繼電器順序控制基礎上發(fā)展起來的以微處理器為核心的通用自動控制裝置。
可編程序控制器是一種數(shù)字運算操作電子系統(tǒng)，專為在工業(yè)環(huán)境下應用而設計。它采用了可編程序的存儲器，用來在其內(nèi)部存儲執(zhí)行邏輯運算、順序控制、定時、計數(shù)和算術運算等操作指令，并通過數(shù)字的、模擬的輸入和輸出，控制各種類型的機械或生產(chǎn)過程？删幊绦蚩刂破骷捌溆嘘P的外圍設備，都應按易于與工業(yè)控制系統(tǒng)形成一個整體、易于擴充其功能的原則設計。
PLC產(chǎn)品種類繁多，其規(guī)格和性能也各不相同。對于PLC，通常根據(jù)其結(jié)構形式的不同、功能的差異和I/O點數(shù)的多少等進行大致分類。
按結(jié)構形式分類
根據(jù)PLC的結(jié)構形式，可將PLC分為整體式和模塊式兩類。
整體式PLC
整體式PLC是將電源、CPU、I/O接口等部件都集中裝在一個機箱內(nèi)，如圖所示。具有結(jié)構緊湊、體積小、價格低的特點。小型PLC一般采用這種整體式結(jié)構。整體式PLC由不同I/O點數(shù)的基本單元（又稱主機）和擴展單元組成，基本單元內(nèi)有CPU、I/O接口、與I/O擴展單元相連的擴展口以及與編程器或EPROM寫入器相連的接口等；擴展單元內(nèi)只有I/O和電源等，而沒有CPU。基本單元和擴展單元之間一般用扁平電纜連接。整體式PLC一般還可配備特殊功能單元，如模擬量單元、位置控制單元等，使其功能得以擴展。
2）模塊式PLC
模塊式PLC將PLC的各組成部分分別做成若干個單獨的模塊，如CPU模塊、I/O模塊、電源模塊（有的含在CPU模塊中）以及各種功能模塊。模塊式PLC由框架或基板和各種模塊組成，模塊裝在框架或基板的插座上，如圖所示。這種模塊式PLC的特點是配置靈活，可根據(jù)需要選配不同規(guī)模的系統(tǒng)，而且裝配方便，便于擴展和維修。大、中型PLC一般采用模塊式結(jié)構。
還有一些PLC將整體式和模塊式的特點結(jié)合起來，構成所謂的疊裝式PLC。疊裝式PLC的CPU、電源、I/O接口等也是各自獨立的模塊，但它們之間是靠電纜進行連接的，并且各模塊可以一層層地疊裝。這樣，不但系統(tǒng)可以靈活配置，還可做得體積小巧。
2.2.按功能分類
根據(jù)PLC的功能不同，可將PLC分為低檔、中檔、。
Woodward Synchronizing System SPM-D Controller 8440-1301 Rev E Model: SPM-D10
Woodward Synchronizer P/N 9907-029 Rev C
Woodward SY2 Synchronisierger?t SY 2 SY2-400-50 Synchronizing Unit SEG 2G
WOODWARD STRTEAMLINE PRODUCTS NH420 **NNB**
Woodward Steuerger?t EPG Speed Control 8290-044 E
WOODWARD STABLIZED EARTH FAULT CURRENT RELAY IRI1ER5HD IRI1 ER5DH ER 5HD
WOODWARD SPM-A SYNCHRONIZER, PN 9905-005, EXC COND
WOODWARD SPM-A SYNCHRONIZER, PN 9905-003, EXC COND
WOODWARD SPM-A SYNCHRONIZER, PN 9905-003, EXC COND
WOODWARD SPM-A SYNCHRONIZER, PN 9905-001, EXC COND
Woodward SPM-A Synchronizer PN 9905-002
WOODWARD SPM-A SYNCHRONIZER MODEL 9905-001 L - CLEAN
Woodward SPM-A Synchronizer 9905-002 REV-P
Woodward SPM-A Synchronizer 9905-002 N
WOODWARD SPM-A SYNCHRONIZER 9905-002
WOODWARD SPM-A SYNCHRONIZER 50/60HZ 10W 9907-028 REV D
WOODWARD SPM-A SYNCHRONIZER 50/60HZ 10W 9905-002 REV N
Woodward SPM-A Synchronizer / Part # 9907-028
Woodward SPM-A Synchronizer / Part # 9905-001
Woodward SPM-A synchonizer 9907-029 REV.B
Woodward SPM-A synchonizer 9907-018 Rev. C
WOODWARD SPM-A (9905-001) SYNCHRONIZER WITH MANUAL
WOODWARD SPM SYNCHRONIZER, PN 8272-385,
WOODWARD SPM SYNCHRONIZER, PN 8271-610, EXC COND
Woodward SPM Synchronizer Model 8271-607A NNB
WOODWARD SPM SYNCHRONIZER 8272-190-C
Woodward Speed Setting Potentiometer Bracket Assembly 5438-121 NOS
WOODWARD SOLENOID VALVE 8402-238
WOODWARD SOLENOID VALVE 8402-214 5852-159
WOODWARD SOLENOID VALVE 5852-130
WOODWARD SOLENOID VALVE 5852-130
WOODWARD SOLENOID SYNCHRO-START # SA-3187 NSN: 5945-01-280-5477 # 1503-24C6U4BS
WOODWARD SOLENOID PART # SA-1637-24 NSN: 5945-01-048-9774
Woodward Servo Postion Controller 8200-226 Rev B
Woodward SEG IRD1-G Transformator Differezialschutz
woodward rotary direct drive vallve
WOODWARD RESISTOR ASSEMBLY # 9900-350 NSN: 5905-01-290-0002
Woodward PWM Gas Trim Valve P/N 8235-622
Woodward PVC Single Receptacle W/Hinged Cover #50-1651 15A 120V Twist Lock ()
WOODWARD PROTECH 203 OVERSPEED PROTECTION SYSTEM 9907-149 ()
Woodward ProTech 203 Overspeed Protection System 9905-990 Rev G With Key
Woodward ProTech 203 Overspeed Protection System 9905-990 Rev G No Key
Woodward Protech 203 Overspeed Protection System 9905-990 Rev G Missing 2 PS
Woodward Protech 203 Overspeed Protection System 8200-203 Rev N
WOODWARD PROTECH 203 OVERSPEED PROTECTION PN 9905-995
WOODWARD PROTECH 203 OVERSPEED PROTECTION PN 8200-301
WOODWARD PROCESS/IMPORT-EXPORT CONTROL, PN 9905-090, EXC COND
WOODWARD Process Import-Export Control (Part #9905-090 H) EXC COND
WOODWARD PREREGULATOR FUSE 3AG.75AMP
Woodward PM Motor Control 8272-536
Woodward Piston Part # 3525-039
WOODWARD PGD GOVERNOR A8556-749 PS, 320-600 RPM, S/N: 1111611 (REFURBISHED)
WoodWard PG Lever Governor S/N: 420991
WOODWARD PEAK 150 DIGITAL STEAM TURBINE CONTROLLER 9905-867 REV-J NNB
Woodward Part # 8272-288 0 Load Sharing Speed Controller 2301A
Woodward Netcon 5000 Input Module 5464-333
WOODWARD NETCON 5000 DISCREET OUTPUT MODULE, EXC COND
WOODWARD NETCON 5000 CPU MODULE, , EXCELLENT COND
WOODWARD NETCON 5000 ACTUATOR DRIVER OUTPUT MODULE,EXC
WOODWARD NETCON 5000 (PART # 5464-588) SERIAL #11459522
WOODWARD MOTOR OPERATED POTENTIOMETER P/N 9900-229 NSN 5905-01-086-2714
Woodward Module 5466-409
WOODWARD MILITARY PGD DIAL GOVERNOR; P/N: 9900-149 ~~GOV~SURPLUS~
WOODWARD MILITARY PG DIAL GOVERNOR; P/N: 9900-149 ~~SURPLUS~
WOODWARD MILITARY P.G. DIAL GOVERNOR; P/N: 9900-149 ~~SURPLUS~
Woodward MFR 11 Multifunktionsrelais Netzüberwachungsrelais Netzüberwachung NEU
Woodward MFR 1 RELAY
Woodward Master Synchronizer and Load Control 9907-004 Rev N
Woodward Master Synchronizer and Load Control 9905-797 Rev M
WOODWARD LOAD SHARING AND SPEED CONTROL, PN 9905-068, EXC COND
WOODWARD LOAD SHARING AND SPEED CONTROL, PN 8272-288, /UN
WOODWARD LOAD SHARING AND SPEED CONTROL 8271-652, EXC COND
WOODWARD LOAD SHARING AND SPEED CONTROL 8271-467, EXC COND
Woodward Industrial Turbine Fuel Control Valve Driver 8200-216
Woodward Hydraulic Governor pn.5178938
Woodward HRT Inc. - Stainless Steel Hydraulic Service Plug - P/N: 41001748 (NOS) Charity item
WoodWard Governors (3) UG 8 (1) PG Lever
WOODWARD GOVERNOR, 8561-252, PSG, 5101888, DETROIT DIESEL
Woodward Governor w/ Bodine Electric Co Motor for Detriot Diesel - P/N: 8561-537
WoodWard Governor UG 8
Woodward Governor Type UG-8 PN: 34381 NOS
WOODWARD GOVERNOR TYPE PG-PL PUMP CONTROL 8552-674,
WOODWARD GOVERNOR TURBINE ELECTRICAL CONTROL ASSEMBLY, MODEL 8230-621
WOODWARD GOVERNOR TM-100 DIGITAL DRIVER DUAL 8200-150
WOODWARD GOVERNOR SPEED SETTING PISTON 361324
WOODWARD GOVERNOR SG GOVERNOR P/N 8511-453 /UN
Woodward Governor Piston Rod P/N 364521
Woodward Governor Piston & Rod P/N 3561-073, 9987-878 NOS
Woodward Governor PG-PL PGPL 8572-565 Un Large Engine Generator Turbine
Woodward Governor PG-PL P/N 8572-212 Waukesha P/N 295493 Brand In Box
Woodward Governor Part # 8240-005 Serial # 1088064
Woodward Governor P/N A8240-449 Diesel Engine REMANUFACTURED
Woodward Governor P/N A8240-298 Diesel Engine
Woodward Governor P/N 1247-007 Connector
Woodward Governor Oil Gauge Site Glass 1832-109 NOS
Woodward Governor Gas Shutoff Valve 9905-451
Woodward GOVERNOR for Military generator p/n 8561-301, 371156, 2990-00-085-5624
Woodward GOVERNOR for Military 100KW Cat Generator MEP007A D333C p/n 8510-212
WOODWARD GOVERNOR FLOW CALIBRATED VALVE CONTROL DIESEL GENERATOR 5233-507
Woodward Governor Field Terminal Module 5437-080
Woodward Governor Field Terminal Module 5437-079
Woodward Governor Field Terminal Module 5437-052
Woodward governor EGB-13P, PN: 8540-381
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