32mA~100mA 0.01~2Sec 4~10A0.01~3sec
0.003~ 3 Sec 0.02 Sec(ma)
FUSING Basics: Hot spot
温度 Temperature(°C)
Melting Point
I >In In
PCB Sn 錫球 負載電流時的溫度 PCB
Basic Fusing Process
1000
100
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TIME IN SECONDS
10
1
0.6
0.1
0.01
10A
0.1
1 10 100 1000 CURRENT IN AMPS
UL/CSA248-1/14規格 V.S IEC60127規格
額定電流(%) 100% 135% 150% 200% 210% 275% 400% 1000% UL&CSA STD 248-1/14 4hr (min) 60 minute (max) ----2 minute (max) ----------------IEC 60127 Sheet 1 --------60 minute (min) ----30 minute (max)
Cat. Fuse Rating =1.91A (最小能選擇的安培數) [計算值]-Absolute minimum fuse rating can be selected. (1206 size 的466 or 468系列2A 以上安培數, 請參考表(一)。) 表 (一)
Catalog Number Ampere Rating Making Code Voltage Rating Nominal Resistance Cold Ohms Melting I t(A2Sec.)2
How to select the Fuse
Fuse Current Carry Capacity per Standards @ 25 ˚C re-rating factor
Max. Carrying current: • UL STD保險絲的最大不熔斷電流是75% In • IEC STD保險絲的最大不熔斷電流是100%In
1.额定電流 Rated Current ( In)
• 額定電流:
In= IR max / (Frf * Tdf)
最大/重載工作電流 (max operating current—IR max) • UL de-rating factor:Frf---0.75 • IEC de-rating factor:Frf----1 •
Tdf:= 0.75*(0.70)
Continue :
應用最大電流(IR max) Cat. Fuse Rating = -------------------------------------- = 0.75 x 溫度折減率(Tdf)@80C 1.0A -----------------------0.75 x 0.70
Remark : For Recognized type supplier’s interrupting rating.
• • • • • •
IEC 60127-2 Breaking Capacity STD All fuse test under 250VAC For LBC must to interrupt a current of 35A minimum and/or 10ln or 100A Maximum For EBC must to interrupt a current of 150A maximum For HBC must to interrupt a current of 1500A maximum Fuse rated in I.R 0 ~1 A 35A (LBC) 1.1 ~3.5A 35A (LBC) 3.6A ~9A 10 ln (LBC) 10.1 ~15A 150A (EBC) 15.1 ~30A 1500A (HBC)
• 選擇的保險絲是主要或次要的保護元件? • (Fuse for Primary or Secondary Protection?) • • • • • • • • 1。額定電流 (Rated current) (Minimum fuse rating)=In 2。應用環境温度 (Ambient temperature) 3。額定電壓 (Rated voltage) AC/DC 4。電壓降 (Voltage drop) 5。熔斷特性 (Fusing characteristics)-時間/電流特性(TC curves) 6。遮斷/分斷能力 (Breaking / Interrupting Capacity) 7。熔化熱能值 ( Melting I²t ) 8。結構特徵 (Structure) ----外形尺寸 ----安裝型式
Cold HOT
• 同時也要求保險絲在超過限量的過載電流時能及時燒斷，其中: Minimum Fusing Current: • UL STD保險絲的最小熔斷電流在 200%In左右 • IEC STD保險絲的最小熔斷電流在 210%左右
選用保險絲的重要參數 (Fuse selection factors)
3 .额定電壓 Rated Voltage( Vr）
• 保險絲的额定電壓應大於或等於應用電路電壓 (Vr標示在 保險絲目錄上) 正常負載時额定電壓對保險絲影響很小 過載熔斷時额定電壓對保險絲有影響
4 保險絲的電壓降
Fuse的電壓降是Fuse在額定電流條件下，其兩端的電壓降。其反映了 Fuse的內阻，其值不應過大。若將內阻（電壓降）過大的Fuse安裝在電 路中，它將影響電路的系統參數，使得電路不能正常工作。Specifications 對標準電壓降不僅有其值的上限規定，而且對其一致性也作了規定。
曲线A：为传统的慢熔断熔丝的曲线; 曲线B：为特快熔断,快熔断和螺旋绕制的熔丝的曲线; 曲线C：自复聚合物保护器的曲线;
室温: 表列熔丝额定值=正常工作主电流/0.75
Ex: 表列熔丝额定值=正常工作主电流/0.75*0.80
Example for Rating Current:
應用電壓: 12 V DC 應用最大/重載電流: 1A @ max 環境溫度緊鄰保險絲: 800C 脈衝電流: 20A @ 30uSec.* 短路電流: 35A max. at 12V 保險絲種類: 1206 size TFF
5 .熔斷特性
-時間/電流特性Time/Current Characteristic
• • 承受過電流時, 電流與熔斷時間的關係 It is a characteristics determine how ห้องสมุดไป่ตู้ast a fuse responds to overcurrents. Over-current is divided into overloads and short circuits.
7 .熔化熱能值 (Melting I2t )
• • 切斷保險絲所需的熱能量值 (Fuse 所能承受的能量值,也是選擇Fuse 重要的參數,即Fuse 必須能承受在 On-Off Inrush Current 的Energy 也是選用保險絲规格的重要参数 防疲勞, 多次的擴散, 氧化 ( prevent de-grade, and oxidize, etc.) Littelfuse 對每一種小型保險絲给出了Fuse Nominal熱熔I2t值
过载和短路
•
UL和IEC的熔斷特性是完全不同的
時間 vs. 電流曲線: (Time vs. Current curve)
.180 1 2 3 5 7.5 15
•
T/C Curve是一個供設計參考用的工具 而非保險絲的規範 是保險絲一個的平均熔斷時間曲線圖. 實際熔斷時間必須考量實際供應電壓 及環境溫度.
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•
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UL 248-14 interrupting rating: All UL Listed fuse rated at 125Vac will have an I.R of 10000A for Subminiature fuse(2AG) ; For fuse rated at 250VAC then it I.R would be rated as below : Fuse rated in 0 ~1 A 1.1 ~3.5A 3.6A ~9A 10.1 ~15A 15.1 ~30A I.R 35A 100A 200A 750A 1500A fuse can refers to the fuse
Arcing event end
6 . Breaking/Interrupting Capacity
• Interrupting rating also know as Breaking Capacity or shortcircuit rating,the interrupting rating is the maximum approved current which the fuse can SAFELY interrupt at rated voltage. The word “safely” here means that there should be no significant damage to the fuse housing nor to the surrounding as a result of arcing or molten metal emerging from the fuse IEC 60127-2 STD Fuse Type have three breaking capacity,High Breaking Capacity(HBC),Enhance Breaking Capacity(EBC) and Low Breaking Capacity (LBC)