一、通信電源為什么是-48V

1、-48V的電源電壓會比較安全一(yi)點：例(li)如人身體是(shi)50K歐姆電阻，電壓-48V，48/50000=0.00096A=0.96mA，人體流過(guo)9mA就(jiu)有生命危險(xian)了。

2、歷史的沿襲：多年前，使用電子管(guan)(guan)和PNP型鍺管(guan)(guan)的時候(hou)，電路(lu)正極接地(di)來得直觀(guan)簡單方(fang)便(bian)。負電源的抗(kang)干擾(rao)性(xing)要(yao)好一些，不過(guo)這是很久以前的原因，現(xian)(xian)在的數字化技術對(dui)這要(yao)求已(yi)不高，所以現(xian)(xian)在設(she)備也有用正電源，但考(kao)慮習慣通用性(xing)大多也還是-48V。

3、電源系統正極(ji)(ji)接地可以減(jian)少蓄電池正極(ji)(ji)的腐蝕現象。

4、降低系統雜音，減少干擾。

5、早期通信可(ke)用大地作回路(lu)，節約線材。

6、為(wei)保護(hu)線纜，使(shi)其(qi)不會由于電池(chi)反應而被腐蝕，線纜必須為(wei)負極(ji)。

7、電(dian)壓比-24V高，有利(li)于電(dian)量傳輸，減少損耗。

二、通信電源系統有哪幾部分組成？

1、交(jiao)流(liu)配(pei)(pei)電(dian)(dian)(dian)(dian)(dian)(dian)單(dan)元：交(jiao)流(liu)配(pei)(pei)電(dian)(dian)(dian)(dian)(dian)(dian)單(dan)元將市(shi)(shi)電(dian)(dian)(dian)(dian)(dian)(dian)接入，經過切換(huan)(huan)送入系(xi)統，交(jiao)流(liu)電(dian)(dian)(dian)(dian)(dian)(dian)經分配(pei)(pei)單(dan)元分配(pei)(pei)后，一部分提供(gong)給(gei)開關整流(liu)器，一部分作為備用輸出，供(gong)用戶(hu)使用。 系(xi)統可以由(you)兩(liang)路市(shi)(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(或一路市(shi)(shi)電(dian)(dian)(dian)(dian)(dian)(dian)一路油機(ji))供(gong)電(dian)(dian)(dian)(dian)(dian)(dian)，兩(liang)路市(shi)(shi)電(dian)(dian)(dian)(dian)(dian)(dian)主備工作方(fang)式，平時由(you)市(shi)(shi)電(dian)(dian)(dian)(dian)(dian)(dian)1供(gong)電(dian)(dian)(dian)(dian)(dian)(dian)，當市(shi)(shi)電(dian)(dian)(dian)(dian)(dian)(dian)1發生(sheng)故障(zhang)時，切換(huan)(huan)到市(shi)(shi)電(dian)(dian)(dian)(dian)(dian)(dian)2（或者油機(ji)），在切換(huan)(huan)過程中，通信(xin)設(she)備的供(gong)電(dian)(dian)(dian)(dian)(dian)(dian)由(you)蓄電(dian)(dian)(dian)(dian)(dian)(dian)池來供(gong)給(gei)。

2、整(zheng)流(liu)(liu)部分：整(zheng)流(liu)(liu)部分的功能是將(jiang)由交流(liu)(liu)配(pei)電單元提供的交流(liu)(liu)電變換成(cheng)48V或者24V直流(liu)(liu)電輸(shu)出到直流(liu)(liu)配(pei)電單元。整(zheng)流(liu)(liu)部分包(bao)括整(zheng)流(liu)(liu)模塊(kuai)和(he)結構部分（機(ji)架(jia)）。

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3、直流配電(dian)(dian)單(dan)(dan)元：直流配電(dian)(dian)單(dan)(dan)元完成直流的分配和備(bei)用電(dian)(dian)池(chi)(chi)組(zu)的接(jie)入(ru)。開關整流器(qi)的輸(shu)(shu)出(chu)經匯流母排(pai)接(jie)入(ru)直流配電(dian)(dian)單(dan)(dan)元，配電(dian)(dian)單(dan)(dan)元為負載(zai)分配不同容量的輸(shu)(shu)出(chu)，可(ke)滿(man)足不同的需要，后備(bei)電(dian)(dian)池(chi)(chi)組(zu)的輸(shu)(shu)入(ru)與開關整流器(qi)輸(shu)(shu)出(chu)匯流母排(pai)并聯，以保證開關整流器(qi)無(wu)輸(shu)(shu)出(chu)時，后備(bei)電(dian)(dian)池(chi)(chi)組(zu)能向負載(zai)供電(dian)(dian)。

4、蓄電池組：通信電(dian)(dian)(dian)源系統(tong)中采用(yong)整流器和蓄(xu)電(dian)(dian)(dian)池(chi)(chi)(chi)組并聯冗余供(gong)電(dian)(dian)(dian)方(fang)式(shi)。蓄(xu)電(dian)(dian)(dian)池(chi)(chi)(chi)組既為備用(yong)電(dian)(dian)(dian)源，又可以吸收高(gao)頻紋波電(dian)(dian)(dian)流。目前常用(yong)的(de)蓄(xu)電(dian)(dian)(dian)池(chi)(chi)(chi)為閥控式(shi)密封(feng)鉛酸蓄(xu)電(dian)(dian)(dian)池(chi)(chi)(chi)，即VRLA，因為較之傳統(tong)的(de)開口型電(dian)(dian)(dian)池(chi)(chi)(chi)密封(feng)性好、自放電(dian)(dian)(dian)小(xiao)、壽命長，又被稱為“免維護蓄(xu)電(dian)(dian)(dian)池(chi)(chi)(chi)”。

5、監(jian)(jian)控(kong)(kong)系統：監(jian)(jian)控(kong)(kong)系統以多級自下而上逐級匯接的(de)方式構(gou)成(cheng)。每個監(jian)(jian)控(kong)(kong)級一(yi)般按輻射方式與若干下級監(jian)(jian)控(kong)(kong)級連接成(cheng)一(yi)點對多點的(de)監(jian)(jian)控(kong)(kong)系統，最低一(yi)級為設(she)(she)備監(jian)(jian)控(kong)(kong)單元（監(jian)(jian)控(kong)(kong)模塊）與其監(jian)(jian)控(kong)(kong)的(de)若干設(she)(she)備的(de)連接。