| 詳細(xì)參數(shù) | |||
|---|---|---|---|
| 品牌 | BrushHawker | 型號 | 961517500MOD5 |
| 結(jié)構(gòu)形式 | 模塊式 | 安裝方式 | 控制室安裝 |
| LD指令處理器 | 硬PLC | 加工定制 | 否 |
Brush Hawker 961517500 MOD 5 勵磁限制器模塊
措施1：采用性能優(yōu)良的電源，抑制電網(wǎng)引入的干擾。
對于PLC控制器供電的電源，應(yīng)采用非動力線路供電，直接從低壓配電室的主母線上采用專用線供電。選用隔離變壓器，且變壓器容量應(yīng)比實際需要大1.2～1.5倍左右，還可在隔離變壓器前加入濾波器。
對于變送器和共用信號儀表供電應(yīng)選擇分布電容小、采用多次隔離和屏蔽及漏感技術(shù)的配電器。控制器和I/O系統(tǒng)分別由各自的隔離變壓器供電，并與主電路電源分開。PLC控制器的24V直流電源盡量不要給外圍的各類傳感器供電，以減少外圍傳感器內(nèi)部或供電線路短路故障對PLC控制器的干擾。
此外，為保證電網(wǎng)饋電不中斷，可采用在線式不間斷供電電源（UPS）供電，UPS具備過壓、欠壓保護功能、軟件監(jiān)控、與電網(wǎng)隔離等功能，可提高供電的安全可靠性。對于一些重要的設(shè)備，交流供電電路可采用雙路供電系統(tǒng)。
措施2：正確選擇電纜的和實施敷設(shè)，消除PLC控制器的空間輻射干擾。
不同類型的信號分別由不同電纜傳輸，采用遠(yuǎn)離技術(shù)，信號電纜按傳輸信號種類分層敷設(shè)，相同類型的信號線采用雙絞方式。
嚴(yán)禁用同一電纜的不同導(dǎo)線同時傳送動力電源和信號，避免信號線與動力電纜靠近平行敷設(shè)，增大電纜之間的夾角，以減少電磁干擾。為了減少動力電纜尤其是變頻裝置饋電電纜的輻射電磁干擾，從干擾途徑上阻隔干擾的侵入，要采用屏蔽電力電纜。
措施3：PLC控制器輸入輸出通道的抗干擾措施。
輸入模塊的濾波可以降低輸入信號的線間的差模干擾。為了降低輸入信號與大地間的共模干擾，PLC控制器要良好接地。輸入端有感性負(fù)載時，對于交流輸入信號，可在負(fù)載兩端并接電容和電阻，對于直流輸入信號可并接續(xù)流二極管。為了抑制輸入信號線間的寄生電容、與其他線間的寄生電容或耦合所產(chǎn)生的感應(yīng)電動勢，可采用RC浪涌吸收器。
輸出為交流感性負(fù)載，可在負(fù)載兩端并聯(lián)RC浪涌吸收器；若為直流負(fù)載，可并聯(lián)續(xù)流二極管，也要盡可能靠近負(fù)載。對于開關(guān)量輸出的場合，可以采用浪涌吸收器或晶閘管輸出模塊。另外，采用輸出點串接中間繼電器或光電耦合措施，可防止PLC控制器輸出點直接接入電氣控制回路，在電氣上完全隔離。
In this example problem, we discuss about both LIC and FIC controllers and what will they do over time if the flow or level transmitter fails or if control valve not working in the loop.
This bwell water level control system for a drinking water treatment facility maintains a constant level of water following filtration, for sourcing to customers:
What LIC and FIC Controllers will do?
Question 1:
Determine what both controllers (LIC and FIC) will do over time if the flow transmitter fails in such a way that it registers zero flow regardless of the actual flow rate of water through it.
Assume the level transmitter is direct-acting (i.e. greater signal with greater water level) and that the control valve is signal- to-open (fail closed).
Question 2:
Determine what both controllers (LIC and FIC) will do over time if the control valve fails in such a way that it ignores the controller’s output and opens wide.
Assume both transmitters are direct-acting (i.e. greater signal with greater flow ; greater signal with greater water level) and that the control valve is signal-to-open (fail closed).
Answer 1:
The flow controller (FIC) will send a “full-open” signal to the valve, because its transmitter indicates the flow rate is less than it should be.
The level controller’s output will saturate low, bling the flow controller to stop the flow as the bwell level rises well above setpoint due to the uncontrolled flow coming in.
Answer 2:
The flow controller (FIC) will send a “close” signal to the valve, because its transmitter indicates the flow rate is excessive.
The level controller’s output will saturate low, bling the flow controller to stop the flow as the bwell level rises well above setpoint due to the uncontrolled flow coming in.
