AC Or DC?

交流還是直流?

Matching the Spark Tester to the Application

            火花測試機的應用匹配   

      How to choose the best spark tester for your application: primary

Insulation﹐twinning﹐bunching﹐taping﹐cabling﹐jacketing or marking.

      在以下不同的工序怎樣選擇合適的火花測試機﹕絕緣﹐束線﹐對絞﹐成纜﹐絕緣包帶﹐外被或印字

Spark testing has long been used on the primary insulation line and at packaging﹐providing first and final insulation quality checks﹒ Increasingly﹐manufacturers are checking for defects prior to or after such interim processes as twinning﹐bunching﹐taping﹐cabling﹐jacketing and marking﹒The following is a discussion of spark tester selection and application﹒

火花測試用于單絕緣﹐包裝已有很長時間了﹐尤其是用于開始或最后的絕緣品質檢測。逐漸的﹐廠商在象對絞﹐束絞﹐包帶﹐成纜﹐外被和印字等中間工序之前或之後檢查產品的缺點。下面將討論火花測試機的選擇和應用。

Spark test equipment is classified by the type of test voltage applied to the product。Available types include Alternating Current(AC) and Direct Current(DC).AC spark testers are of two types---those that operate at power mains frequencies (generally 50 or 60 Hz) and high-frequency types that operate at frequencies between 500 Hz and 3 kHz﹒Impulse testers﹐which are no longer in common use﹐are not discussed.

火花測試設備是通過施加于產品的電壓種類來分類的﹐使用的電壓種類包括交流電壓和直流電壓。交流電壓火花測試機包括兩種型號---工作于電力基本頻率(通常為50或60赫茲)的工頻火花機和工作于頻率介于500到3千赫茲的高頻火花機。脈沖波形火花測試機已不常用﹐這里不予討論。

Advantages of AC Spark Testing

交流火花測試機的優點

AC spark testers create a field of ionized air (a blue-colored glow called corona) around the product. The corona is electrically conductive and provides a good test even when the bead chains are not making physical contact. Corona is caused in part by the AC voltage changing from positive to negative with each cycle. For this reason, high frequency spark testers generate more corona than 60 cycle testers.

交流火花測試機使產品周圍的空氣電離(一種藍色的電暈)形成電場。這電暈是

可導電的,提供了一種良好的測試﹐即使當電極珠鏈沒有被連接到時。電暈是由于交流電在每個周期內由正向轉向負向時產生的。由于這些原因﹐高頻火花機產生的電暈比60赫茲的更多。

Also, a by-product of the corona is heat. If you were to leave a grounded cable stationary in an energized high-frequency electrode for a while, you would notice that the insulation is noticeably warmer where it made contact with the corona field. This heating helps to break down weak spots in the dielectric that otherwise might pass through the electrode undetected, only to fail during a later spark or hipot test.

又由于﹐靠近電線制品的電暈是熱的。如果我們將一根接地電纜穩定放在施以高頻電極電壓的電極中一會兒﹐你將注意到與電暈有接觸的絕緣部分有明顯的變熱。這熱量幫助擊穿電線絕緣較薄的地方﹐否則線材通過電極而沒有被檢測到﹐結果在以后的火花測試和高壓絕緣試驗將會失效。

Disadvantages of AC Spark Testing

交流火花機的缺點

In wires with very weak insulation (such as telecom and datacom wires having a foamed dielectric), the AC voltage ionizes the air inside the foam cells, reducing overall dielectric strength of the insulation. The insulation may then fail, damaging the product. This is particularly true with high-frequency spark testers that should not be used with foamed insulation.

絕緣較薄的電線(如具有發泡絕緣的通信和網絡電纜)﹐交流電壓使發泡單元里的空氣電離﹐這將減少絕緣的介電強度。這絕緣將失效﹐最終將損壞這產品。因此高頻火花機不被應用于發泡絕緣是非常正確的。

When the capacitance of the product in the electrode is very high, a leakage current forms. Because capacitance is more a function of the ratio of conductor size to insulation thickness than to overall size﹐products that produce high capacitance can include cables with large conductors and thin insulation, small wires with very thin dielectric or multiple conductors going through the same electrode(e.g., tape and ribbon cables).For safety reasons, the spark tester’s current output is limited to 4 to 6 milliamps. When the leakage current reaches this level, there is no more available supply current to generate a greater test voltage. The maximum possible voltage attainable with that product may not be high enough to provide a good test.

當在電極中的電線產品的電容特別高時﹐將形成泄漏電流。因為此電容是導體尺寸與絕緣厚度比值的函數﹐例如大導體薄絕緣電纜,或薄絕緣的有非常小介電常數的小電線或多根導體的電線,通過同樣的電極時將產生很高的電容(帶狀電纜)。為了安全起見﹐火花機的電流輸出被限制在4~6毫安。當泄漏電流達到這水平時﹐火花機將再也不能有效輸出電流來產生高的測試電壓。對于某種電線﹐能達到的最大可能電壓將不夠提供很好的測試。

Advantages of DC Spark Testing

直流火花機的好處

DC spark testing generates practically no corona and no heat, and is therefore a gentler test process, DC can be used on foamed insulation and thin insulation.

DC technology has no problem with capacitance. Very large wires and multiple conductors can be tested with one power supply. DC spark testers are often used in cabling operations, sometimes testing 25 twisted pairs within a single electrode.

直流火花機几乎不能產生電暈和熱量﹐因此它是一種輕微的測試方法﹐直流火花機可用于發泡和薄的絕緣。

直流火花機技朮對用于電容沒有問題。非常大的電線和多根導體的電線可以用一台設備來測試。直流火花機常被用于成纜﹐有時在單個電極中測試25對的電纜。

Disadvantages of DC Spark Testing

直流火花機的缺點

The product must be grounded! The center conductor or shield should be grounded for reasons of safety and efficacy. If the product is not grounded and a fault passes through the electrode﹐the spark tester will count, but the entire reel will become charged to high voltage and will maintain this potential until something discharges it. Subsequent faults may not be detected because the center conductor will be nearly the same potential as the electrode, and detection circuits require differentiation.

電線必須接地﹗因安全和有效性原因﹐中央導體或屏蔽必須接地。如果未接地和有破點的電線通過電極時﹐火花機將計數﹐但是整卷將被充上高壓和保持這種電壓直到某種物體使它放電。由于中央的導體的電位幾乎與電極的電位相同,後面的缺限將不能被檢測出來.因為檢測電路要有電位差(譯者:電壓可以理解為電位差)。

A different test voltage must be used as compared with AC (1.414xAC RMS Voltage=DC Peak voltage).This is not really a disadvantage, but a difference in the way the two types of voltage are measured, AC is measured in RMS (root means squared) while Dc is measured as Peak Voltage.

同樣的測試,與交流電壓相比較﹐直流測試電壓數值是不同的(1.414 X有效值電壓=直流峰值電壓)。這不是一個真正的缺點﹐而是兩者的計量方式不同,交流電壓是以有效值來計量而直流電壓是以其峰值來計量的。

Guide to Selection

選擇指引

      Clinton Instrument Company offers a variety of spark tester models engineered to meet most wire and cable applications. Both DC and AC model spark testing machines are manufactured by the company. Clinton’s DC spark tester models include the STB-STH-STM Series for the following applications:

       克林頓公司提供了許多種型號的火花機工程模塊來滿足大多數電線和電纜的應用。該公司直流和交流火花機兩種型號都生產。克林頓直流火花機包括STB-STH-STM系列,應用于以下產品﹕

l          Small conductors with solid or foamed insulation where the center conductors can be reliably grounded.

l          Multiple conductors in twinning, bunching or cabling operations where each conductor must be reliably grounded.

l          Very large cable jackets that are tested at 50kVDC or less up to 125mm (4.9’’). with this Series the center conductor or cable jacket must be grounded.

l          具有小導體的實心或發泡線,中央導體能可靠接地。

l          多根導體,在對絞﹐束線或成纜工序中,絞合導體必須被有效接地。

l          具有被50KV直流所測試的大電纜的外被或至少超過125毫米(4.9英寸),導體必須接地。

Clinton AC (high-frequency-3 kHz) Model HF-20G Series spark testers are designed for the following applications:

克林頓交流(3千赫茲高頻)模塊 HG-20G系列火花機有以下應用﹕

l  Products with solid insulation (not foamed) in gauge size roughly from 26 to 2 AWG (0.13 to 33.6 mm²).

l   Larger wires and cable jackets tested at 15 KV or less (test voltages dependent on product capacitance).

l   Small unjacketed cables or bunches tested for bare wire or splices (test voltage dependent on product capacitance).

l   具有實心(沒有發泡)絕緣的產品大小規格大約在26~2號線規(0.13到33.6平方毫米)

l   大的電線和電纜的外被被15千赫茲或以下所測試(測試電壓依靠產品的電容確定)

l   小的沒有外被的電纜或束線測試它的裸導體或接合處(測試電壓取決于產品的電容)

Clinton AC (60 cycle) Model STA-30G Series spark testers are designed for the following applications:

克林頓交流火花機(60赫茲)的STA-30G系列火花機有以下應用﹕

l   Larger power cables or cable jackets that are tested at 30 KV or less (the test voltages are dependent upon the product capacitance).

l   Larger unjacketed cables or bunches that are tested for bare wire or splices (the test voltages are dependent upon product capacitance).

l   大的電源線或電源線的外被在30千伏或以下電壓測試(測試電壓取決于產品的電容)

l   大的沒有外被的電纜或束線測試它的裸導體或接合處(測試電壓依靠產品的電容確定)。