Use three of these to protect each busbar feed - suggest 25 or 30A.
( I assumed 5V and 300W so total current is 60A. Each feed then conducts 20A. If one feed fails then current divides between remaining two to 30A each which is sensible safe limit for 4mm2. If only one feed then 60A through 4mm2 is excessive and current trip operates. This type of trip has visual indication of overcurrent event - push button is out. They also have low contact resistance 0.006 and 0.004 Ohms respectively so volts drop at 20A is circa 20 x 0.005 = 0.1V.)
Anyway - some ideas for you to mull over. There will be other schemes one can think of but this is mine.
http://www.farnell.com/datasheets/5...VPjTF3_QxYzo_V5PNaSPK2XNI44u5mIBoCW-gQAvD_BwE
( I assumed 5V and 300W so total current is 60A. Each feed then conducts 20A. If one feed fails then current divides between remaining two to 30A each which is sensible safe limit for 4mm2. If only one feed then 60A through 4mm2 is excessive and current trip operates. This type of trip has visual indication of overcurrent event - push button is out. They also have low contact resistance 0.006 and 0.004 Ohms respectively so volts drop at 20A is circa 20 x 0.005 = 0.1V.)
Anyway - some ideas for you to mull over. There will be other schemes one can think of but this is mine.
http://www.farnell.com/datasheets/5...VPjTF3_QxYzo_V5PNaSPK2XNI44u5mIBoCW-gQAvD_BwE
