It is common to find fuse couple with MOV in AC power circuit. Assuming SPD paralleled in post circuit becomes paralyzed under the condition of short-circuit , fuse ofen fails to keep circuit open, so current continues to flow through MOV.When heating is up to certain level, it results in circuit catching fire,which is a nightmare for customer who demands high reliability on power module.
This PPT explains the backgournd of BCD development,compares the performance between Bencnet BCD solution and multiple convetional solutions on AC power port protection, and illustrate the relationship of cutting off time and current magnitude.
2. 1. Background
3. Test Process
2. Test comparison and analysis of multiple solutions
4. Circuit cut off time and current for BCD test
Menu
5. Recommended solution of BCD product
3. 1. Background---Risks Originated from Conventional Application
1. The rated current of fuse which in series in the circuit of power, should be higher
than normal working current and withstand surge current. Assuming SPD
paralleled in post circuit becomes disabled in short-circuit condition, fuse in primary
circuit, it is possible not open and result in circuit catching fire.
2. Ground potential will rise up when extremely high voltage or lightning hit the
ground. Because of the ground impedance(main) or uncertain factors(minor),
current may reversely strike power network. In this situation, GDT in power port
generates high temperature up to 1000℃ when breakdown last a while( 20A / 5S),
and MOV catches fire finally.
Earthing Resistance
4. 2.Test Comparison and Analysis of Multiple Solutions
FUSE
+MOV
+GDT
failOK OK
MOV
+T-GDT T-MOV
MOV
+BCD
fail
Circuit
Diagram
Circuit Open
Time@20A
Stability
Process
Reliability
ITEM
6. 3. Test Process- Alternative Solution of Others
Earthing Resistance
T-MOV1 T-MOV2
T-MOV3
T-MOV can not break the circuit @1000V 20A condition, also it generates the voltaic arc during the fire.
T - MOV
Test Environment:1000V 20A
7. Earthing Resistance
MOV2 MOV3
MOV1
MOV + BCD
MOV+ Heat Shrinkable Tube +BCD
BCD
Bencent newly-developed part BCD could cut off the circuit rapidly
and block the current . Test shows not a single firelight could be
identified under the harsh condition of 40A thanks to wrapping heat
shrinkable tube on BCD.
Test Environment:1000V 20A
3. Test Process- Alternative Solution of Bencent
Test Environment:1000V 40A
8. 4.Circuit cut off time and current for BCD test
MOV
Adjustable Resistance
AC1200V
BCD
CircuitCut-offTime(s)
Current(A)
9. 5. Recommended Solution of BCD product
Above is circuit diagram for AC power which is common
to see in telecommunication and industrial application.
Fuse 1 for L and Fuse 2 for N, Fuse 3 for Safety fuse . If
F1 and F2 has to pass impulse current 5KA@8/20us, then
the I2
t of fuse has to be more than 1000 A2
s resulting in
15A static current flowing through fuse.
Above are the recommended circuit diagrams with BCD, left for differential
mode(DM)protection, right for common mode(CM) integrated protection . Both
solutions can save fuses (F1 for L, F2 for N). GDT can keep open both in CM and DM
even when MOV fails. BCD can withstand the lightning level more than 10KA and
disengaging at power current @1A.
This solution features
1.to provide simplified solution and save space in PCB layout,
2. to provide fast responsiveness to cut off circuit to prevent fire.
10. Thank you!
Shenzhen Bencent Electronics Co.,Ltd.
ADD: 5/F, Building 1, Hainengda Industrial Park,
Baolong 4th road, Longgang , Shenzhen, China 518116
Email : overseamarket@bencent.com.cn
bencent1999@gmail.com
TEL: 0086 755 2651 5078
The End.
