一、通信電源為什么是-48V

1、-48V的電源電壓會(hui)比較(jiao)安全一點：例如人(ren)身體是50K歐姆電阻，電壓-48V，48/50000=0.00096A=0.96mA，人(ren)體流過9mA就有生命(ming)危險了。

2、歷史的(de)沿襲：多年前(qian)，使用(yong)電子管和PNP型鍺管的(de)時候，電路正極接(jie)地來(lai)得(de)直觀(guan)簡單(dan)方(fang)便。負電源(yuan)的(de)抗干(gan)擾性要(yao)好一些，不過這是很久(jiu)以前(qian)的(de)原(yuan)因(yin)，現在的(de)數字化技術對這要(yao)求已不高(gao)，所(suo)以現在設備(bei)也(ye)有用(yong)正電源(yuan)，但考(kao)慮習(xi)慣通用(yong)性大多也(ye)還是-48V。

3、電源系(xi)統正(zheng)極接地可以(yi)減少蓄電池(chi)正(zheng)極的腐蝕(shi)現象。

4、降低系(xi)統雜音(yin)，減少干擾。

5、早期通信可用大地(di)作回路，節(jie)約線材(cai)。

6、為保護線纜(lan)，使其不會由于電池反(fan)應而被腐蝕，線纜(lan)必須為負極。

7、電壓比-24V高，有利于電量(liang)傳輸，減少(shao)損耗(hao)。

二、通信電源系統有哪幾部分組成？

1、交(jiao)流(liu)(liu)配電(dian)(dian)(dian)(dian)(dian)(dian)單元：交(jiao)流(liu)(liu)配電(dian)(dian)(dian)(dian)(dian)(dian)單元將市(shi)電(dian)(dian)(dian)(dian)(dian)(dian)接入(ru)，經過切(qie)(qie)換(huan)送(song)入(ru)系統，交(jiao)流(liu)(liu)電(dian)(dian)(dian)(dian)(dian)(dian)經分(fen)配單元分(fen)配后，一(yi)(yi)部分(fen)提供給(gei)開關整(zheng)流(liu)(liu)器，一(yi)(yi)部分(fen)作為(wei)備用(yong)輸出，供用(yong)戶使用(yong)。 系統可以由(you)兩(liang)路市(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(或一(yi)(yi)路市(shi)電(dian)(dian)(dian)(dian)(dian)(dian)一(yi)(yi)路油機)供電(dian)(dian)(dian)(dian)(dian)(dian)，兩(liang)路市(shi)電(dian)(dian)(dian)(dian)(dian)(dian)主備工作方(fang)式，平時由(you)市(shi)電(dian)(dian)(dian)(dian)(dian)(dian)1供電(dian)(dian)(dian)(dian)(dian)(dian)，當(dang)市(shi)電(dian)(dian)(dian)(dian)(dian)(dian)1發生(sheng)故障時，切(qie)(qie)換(huan)到市(shi)電(dian)(dian)(dian)(dian)(dian)(dian)2（或者油機），在切(qie)(qie)換(huan)過程中，通(tong)信設備的供電(dian)(dian)(dian)(dian)(dian)(dian)由(you)蓄(xu)電(dian)(dian)(dian)(dian)(dian)(dian)池來(lai)供給(gei)。

2、整流(liu)部分(fen)：整流(liu)部分(fen)的功能(neng)是(shi)將由(you)交流(liu)配(pei)電(dian)單(dan)元(yuan)提供的交流(liu)電(dian)變(bian)換成48V或者24V直(zhi)流(liu)電(dian)輸出到直(zhi)流(liu)配(pei)電(dian)單(dan)元(yuan)。整流(liu)部分(fen)包括整流(liu)模塊和結構部分(fen)（機架）。

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3、直流(liu)(liu)(liu)配電(dian)(dian)單元：直流(liu)(liu)(liu)配電(dian)(dian)單元完成直流(liu)(liu)(liu)的分配和備用(yong)電(dian)(dian)池(chi)組(zu)的接入(ru)。開(kai)關整流(liu)(liu)(liu)器的輸出經匯流(liu)(liu)(liu)母排接入(ru)直流(liu)(liu)(liu)配電(dian)(dian)單元，配電(dian)(dian)單元為負載分配不同容量的輸出，可滿足不同的需要，后備電(dian)(dian)池(chi)組(zu)的輸入(ru)與開(kai)關整流(liu)(liu)(liu)器輸出匯流(liu)(liu)(liu)母排并聯，以(yi)保證(zheng)開(kai)關整流(liu)(liu)(liu)器無輸出時，后備電(dian)(dian)池(chi)組(zu)能向負載供(gong)電(dian)(dian)。

4、蓄電池組(zu)(zu)：通信電(dian)源(yuan)系統(tong)中采用(yong)整流器(qi)和蓄電(dian)池(chi)(chi)組(zu)(zu)并聯冗余(yu)供電(dian)方式。蓄電(dian)池(chi)(chi)組(zu)(zu)既為(wei)備(bei)用(yong)電(dian)源(yuan)，又(you)可以吸(xi)收高(gao)頻(pin)紋波電(dian)流。目前常用(yong)的蓄電(dian)池(chi)(chi)為(wei)閥(fa)控式密封(feng)鉛酸蓄電(dian)池(chi)(chi)，即VRLA，因為(wei)較之傳(chuan)統(tong)的開口型電(dian)池(chi)(chi)密封(feng)性(xing)好、自放電(dian)小(xiao)、壽(shou)命長(chang)，又(you)被稱為(wei)“免(mian)維(wei)護蓄電(dian)池(chi)(chi)”。

5、監(jian)(jian)控(kong)(kong)(kong)(kong)系(xi)統：監(jian)(jian)控(kong)(kong)(kong)(kong)系(xi)統以多級(ji)(ji)自下(xia)而上逐級(ji)(ji)匯接(jie)的(de)方(fang)式構成(cheng)。每個監(jian)(jian)控(kong)(kong)(kong)(kong)級(ji)(ji)一(yi)(yi)般按(an)輻射方(fang)式與若干(gan)下(xia)級(ji)(ji)監(jian)(jian)控(kong)(kong)(kong)(kong)級(ji)(ji)連(lian)接(jie)成(cheng)一(yi)(yi)點對多點的(de)監(jian)(jian)控(kong)(kong)(kong)(kong)系(xi)統，最(zui)低一(yi)(yi)級(ji)(ji)為(wei)設(she)備監(jian)(jian)控(kong)(kong)(kong)(kong)單元（監(jian)(jian)控(kong)(kong)(kong)(kong)模塊）與其監(jian)(jian)控(kong)(kong)(kong)(kong)的(de)若干(gan)設(she)備的(de)連(lian)接(jie)。