Asking the determination of cable sizing

[yn_wong]

According to rule ,

Iz > In > Ib and 1.45Iz > I2 , Where

Iz= design current of circuit ,
In= norminal current of protective device,
Ib= current capacities of conductor.
I2=fusing current of protective device.

If I have a circuit from a Fuse-630A protection connecting in a series , and through a VFD starter with overload protection -390A to 430A then to a motor drive-415A.

From above condtion of protective device ( ie Fuse and VFD Overload  , Which one should be take for In ?? How to determine the cable size ???

If anyone know please kindly let me know !
Many thanks

Nam    

[ip-BEN-BY_WEBMASTER]

yn wong
   閣下才高八斗,滿篇英國澇溲,果然聲勢迫人!
   如用閣下國家語文(中文)發表,是否更加恰當呢?
   讓更多會員分享,發表,會否好o的呢?
   請?踾\電力裝置實用手冊(萬里書店出版)有您要的答案.
   另閣下文章內的計算公式與原公式有多少出入,(留意數學符號)
   煩請作適當更正.

[Tandy]

       

yn_wong 寫道:
According to rule ,

Iz > In > Ib and 1.45Iz > I2 , Where

Iz= design current of circuit ,
In= norminal current of protective device,
Ib= current capacities of conductor.
I2=fusing current of protective device.

If I have a circuit from a Fuse-630A protection connecting in a series , and through a VFD starter with overload protection -390A to 430A then to a motor drive-415A.

From above condtion of protective device ( ie Fuse and VFD Overload  , Which one should be take for In ?? How to determine the cable size ???

If anyone know please kindly let me know !
Many thanks

Nam    

根據基本法第九條使用英文或中文是絕對無問題的，不過在裡發表文章最好都是用中文。遷就一下我這類讀完小學就出來學師的老一輩電燈佬或英文水平不高的工友，等我們都學???洁C
等我試一下攪攪這篇〝鷄腸〞，攪得唔好請各位同業先進幫幫手。

問：根據由大到小排列的方案，選擇電纜的載面積以附合規定？  

Iz > In > Ib 和 1.45 Iz > I2

Iz= 導體的載流量
In= 保護器件的標稱電流
Ib= 設計電路的電流
I2= 保護器件的有效操件電流

假如有一由 630A 熔斷器保護的電路，供給一台有啟動裝置連 390A~430A 過載保護器連接的馬達，馬達滿載電流為 415A。

請問從上面保護裝置的條件，從那裡選擇In去選配Iz？


答：（430A）   :idea:
注意Iz 要考慮各種因數配合。

另 yn wong 工友 Iz 同 Ib 的註解調轉?髐峖釣潃荂?鷄腸〞寸錯字請修正。


   :roll: IP 工友 (數學符號) 我已幫手改進，但網業出唔倒？ :-?

[yn_wong]

謝謝 Tandy 巳,

Personally , I am not like typing chinese since very complicate ( let to be sometime to learn chinese key in ) ,!

Refer to my question,
 
As you write , the Iz -cable size will be determined by 430A, Why we don't use fuse -630A for determination the cable size ??

Many thanks

yn wong 工友上

[Tandy]

yu wong:

因你沒有具体說明它們之間的距離，選擇 430A 是有限制性，由熔斷器至啟動器電纜不能長過 3M，啟動器至馬達無限制。

如由熔斷器至啟動器電纜超過 3米及比較遠，我選擇不如換?鰼? FUSE 好過，又或是把啟動器連過載保護器安裝在熔斷器旁，再造遙遠控掣器在馬達旁。

[ip-BEN-BY_WEBMASTER]

yu wong
        ＞≠≧
        另VFD是否Variable Frequency Device 的簡稱,
        小弟識字唔多,請多多指教.
   

[yn_wong]

ip  

You are right !
VFD=Variable Frequency Device ,
=================================

Tandy,

Thanks for your reply, Refer to my question, I have following information , The fuse and VFD is inside a local control panel ( there distance is within 3 metres... ) , and a motor drive is outside away from the local control panel about 60 Meters long , then , According to COP , which devices ( Fuse or Overload from VFD) treat as protective devices for determination of cable size to the motor drive ?

YN

  :-o  :hammer:  :hammer:  :hammer:

[Tandy]

yu wong 工友：

現在知到你全套裝置的電路安排，那就易辦。
電纜大小取決於 430A 是完全符合工作守則的，至於你所問為何須要安裝 630A 熔斷器，原因有兩個。
1.考慮馬達的起動電流。
以本人愚見同級的熔斷器在 I2 (熔斷電流) 內是可以容忍到馬達的起動電流。
但一般機械工程人員在設計的上游過載保護都會用大一点，因永遠無?癆i。
2.調速器所產生的諧波電流。
因馬達用變頻調速器做控制，調速器是會長時間產生大量諧波電流，會把同級的過載保護裝置斷開。


IP 工友：
我終於做到這幾個"數學符號"   > , Iz , In ,Ib ,I2

不是這幾個＞≧≠，原來在寫文章上面的功能部份可幫到手，不過都幾煩。\r
 :sante:

[yn_wong]

謝 謝 Tandy 工友回答....! :sante: