Nyob rau hauv niaj hnub kev lag luam automation thiab tswj tshuab, tswj cables yog qhov tseem ceeb ntawm lub paj hlwb, xa cov cim tseem ceeb thiab lub zog rau cov tshuab, sensors, thiab programmable logic controllers (PLCs). Kev tiv thaiv kev lag luam cable yog ib hom tshwj xeeb tsim los tiv thaiv cov cim tseem ceeb ntawm kev cuam tshuam sab nraud electromagnetic (EMI) thiab tiv thaiv lub cable nws tus kheej los ntawm kev cuam tshuam. Nyob rau hauv lub plawv ntawm nws functionality yog ib qho tseem ceeb ntawm installation xyaum: tsim nyog shielding txheej grounding. Phau ntawv qhia no piav qhia txog qhov muaj pes tsawg leeg ntawm cov cables no, qhov tseem ceeb ntawm kev cog qoob loo ntawm lawv cov ntaub thaiv npog, thiab cov txheej txheem txheej txheem tom qab ib qho - taw tes rau ob- taw tes hauv av txheej txheem.
Anatomy ntawm Shielded Industrial Control Cable
Ib tug raug shielded tswj cable muaj ob peb yam tseem ceeb:
- Tus neeg xyuas pib / Core:Cov tooj liab lossis txhuas hlau uas nqa cov teeb liab hluav taws xob lossis lub zog.
- Rwb thaiv tsev:Surrounds txhua tus neeg xyuas pib txhawm rau tiv thaiv luv luv.
- Inner Shield (Yeem):Feem ntau ib txheej txheej conductive (xws li, aluminized polyester daim kab xev, semiconductor daim kab xev) tso ncaj qha rau insulated conductors. Nws lub luag haujlwm tseem ceeb yog kom sib npaug ntawm qhov hluav taws xob nyob ib puag ncig ntawm tus neeg xyuas pib, ua kom tsis muaj qhov tsis sib xws uas tuaj yeem ua rau muaj kev ntxhov siab hauv cheeb tsam ntawm lub rwb thaiv tsev.
- Outer (tag nrho) Shield:Thawj txheej tiv thaiv tiv thaiv EMI. Qhov no feem ntau yog braided tooj liab mesh, ib daim kab xev siv tooj liab, lossis ob qho tib si ua ke. Cov ntaub thaiv npog no encases tag nrho cov insulated cores.
- Jacket / Sheath:Cov txheej txheej sab nrauv, ua los ntawm PVC, polyurethane, lossis lwm yam khoom siv, muab cov khoom siv kho tshuab, tshuaj, thiab kev tiv thaiv ib puag ncig. Cov txheej tiv thaiv sab nrauv yog qhov tseem ceeb rau kev coj ua hauv av txhawm rau tiv thaiv suab nrov.
Qhov tseem ceeb ntawm Shield Grounding: Combating Electromagnetic Interference (EMI)
Lub hom phiaj tseem ceeb ntawm kev siv cov ntaub thaiv kab thaiv hauv av yog tsim kom muaj - txoj kev impedance qis rau lub ntiaj teb rau kev cuam tshuam kev cuam tshuam. Nyob rau hauv ib puag ncig kev lag luam, kev tswj cov kab hluav taws xob feem ntau khiav nrog lub hwj chim cables, motors, variable zaus drives (VFDs), thiab lwm yam high - khoom siv hluav taws xob uas tsim muaj zog electromagnetic teb. Yog tsis muaj cov ntaub thaiv npog hauv av, cov teb no tuaj yeem ua rau tsis xav tau qhov hluav taws xob thiab cov khoom siv tam sim no (suab nrov) hauv cov kab hluav taws xob tswj cov teeb liab, ua rau:
- Cov ntaub ntawv tsis raug cai lossis teeb liab yuam kev
- Malfunction ntawm cov khoom rhiab heev
- Kev coj tus cwj pwm tsis zoo thiab cov txheej txheem tsis ruaj khov
- Txo kev cia siab thiab nce downtime
Ib daim ntaub thaiv npog zoo ua raws li lub tawb Faraday, cuam tshuam qhov EMI sab nraud thiab cuam tshuam nws mus rau hauv av ua ntej nws tuaj yeem nkag mus rau cov khoom siv sab hauv.
Kev txheeb xyuas ib leeg-End vs. Ob npaug-End Shield Grounding
Kev xaiv ntawm txoj hauv kev hauv av- txuas cov ntaub thaiv npog ntawm ib qho kawg (ib zaug -taw tes) lossis ob qho kawg (ob-taw tes)- yog qhov kev txiav txim siab tseem ceeb nrog rau kev cuam tshuam tseem ceeb.
1. Lub hauv paus ntsiab lus thiab txiaj ntsig ntawm Ob -Point Grounding
Cov ntawv qub yog qhia txog qhov tseem ceeb ntawm kev cog qoob loo ntawm ob qhov kawg ntawm daim ntaub thaiv. Thaum ib qho kev cuam tshuam sib nqus teb hla hla ib kab, nws ua rau lub suab nrov nrov raws qhov ntev ntawm ob lub teeb liab xov hlau thiab daim thaiv. Yog hais tias lub shield yog grounded ntawm ob qhov kawg, qhov induced voltage ua rau ib tug tam sim no ntws raws lub shield nws tus kheej. Raws li Lenz txoj cai lij choj, cov ntaub thaiv npog tam sim no ua rau nws tus kheej tawm tsam qhov sib nqus, uas tshem tawm ib feem tseem ceeb (feem ntau tshaj 99%) ntawm qhov chaw cuam tshuam thawj hauv daim ntaub thaiv. Qhov no yog hu ua "kev tiv thaiv kev ua tau zoo" thiab yog lub tswv yim zoo rau kev txo qis - zaus sib nqus teb cuam tshuam (xws li, los ntawm cov kab hluav taws xob, transformers).
2. Qhov Kev pheej hmoo thiab kev txiav txim siab rau ob -Point Grounding
Txawm li cas los xij, grounding ob qhov kawg tsim ib lub voj kaw rau cov ntaub thaiv npog. Qhov no qhia txog ob qhov kev pheej hmoo uas yuav muaj:
- Ground Loop Currents:Yog hais tias cov ntsiab lus hauv av ntawm ob qho kawg ntawm cov kab hluav taws xob sib txawv me ntsis (ib qho hauv cov nroj tsuag loj), qhov tam sim no tsis tu ncua yuav ncig hauv daim ntaub thaiv. Qhov tam sim no tuaj yeem dhau los ua qhov cuam tshuam rau cov teeb liab xov hlau.
- Fault Currents:Thaum lub tshuab hluav taws xob tsis raug lossis hluav taws xob tawm tsam, cov dej loj, ntu ntu tuaj yeem ntws los ntawm cov av hauv av. Yog tias daim thaiv thaiv txuas ntawm ob qhov kawg, cov dej ntws no yuav pom txoj hauv kev los ntawm cov ntaub thaiv npog cable, uas ua rau muaj kev puas tsuaj thiab nthuav tawm cov hluav taws xob txaus ntshai.
3. Daim Ntawv Qhia Txog Daim Ntawv Thov: Thaum twg yuav siv txoj kev twg
- Siv daim ntaub thaiv npog ntawm ob qhov kawg:Qhov no feem ntau pom zoo rau cov teeb liab analog (4-20mA, thermocouples) thiab digital kev sib txuas lus raws tu qauv (RS-485, Profibus, Ethernet) nyob rau hauv ib puag ncig uas sib nqus cuam tshuam yog qhov tseem ceeb ntawm kev txhawj xeeb, muab qhov zoo, ib qho chaw hauv av kom txo tau qhov sib txawv. Nws tseem yog cov qauv kev coj ua rau cov cables siv hauv kev tiv thaiv relay thiab automation circuits nyob rau hauv high-voltage substations, qhov twg mitigating transient electromagnetic cuam tshuam los ntawm switchgear ua hauj lwm yog qhov tseem ceeb.
- Ground the Shield ntawm Ib Qhov Kawg nkaus xwb (feem ntau yog Control Vaj Huam Sib Luag Kawg):Txoj hauv kev no feem ntau yog siv rau qis - zaus digital I/O cov cim qhia thiab yog txoj hauv kev nyab xeeb tshaj plaws kom tsis txhob muaj cov voj voog hauv av. Nws rhuav tshem txoj kev circulating tam sim no. Txawm tias me ntsis tsis zoo tiv thaiv kev cuam tshuam sib nqus, nws zoo heev tiv thaiv capacitive (hluav taws xob) coupling. Txoj kev no yooj yim dua thiab zam kev pheej hmoo cuam tshuam nrog qhov sib txawv ntawm cov ntsiab lus hauv av.
Xaus
Kev cog qoob loo ntawm kev lag luam kev lag luam cable tiv thaiv txheej tsis yog ib qho kev xaiv tab sis yog ib qho tseem ceeb uas yuav tsum tau ua kom muaj kev ncaj ncees thiab teeb pom kev ncaj ncees. Kev xaiv ntawm ib qho -point thiab ob-point grounding yuav tsum yog raws li:
- Hom teeb liab raug xa mus (analog vs. digital, low-speed vs. high-speed).
- Qhov tseem ceeb ntawm qhov chaw electromagnetic (magnetic vs. electric fields).
- Qhov zoo thiab sib xws ntawm cov nroj tsuag hauv av.
Hu rau peb pab neeg txhawb nqa ncaj qha rau kev sab laj. Cia peb pab koj tsim lub suab nrov - tiv taus thiab txhim khu kev qha tswj system.
