1. UEENEEE003B Solve Problems in Single Path DC Circuits Protection Devices

2. There are two types or fuses: SERFs semi enclosed rewireable fuses HRCs high rupturing capacity RATED VALUES Current rating Fault current rating Current Rating is the current value that will cause the fuse to blow. Fault Current Rating is the maximum current value that the fuse can interrupt. 8/9/2011 Revision02 2 Fuses

3. Fault Current The fault current will cause the element to melt. This heat causes the sand to melt. The sand quickly cools and forms an insulating barrier to cut the arc. 8/9/2011 Revision02 3

4. For common applications Circuit Breakers can be classified as: magnetic thermal thermal magnetic Circuit Breakers offer the best reset, after the fault has been cleared. Circuit breakers are common in domestic, commercial and Industrial installations 8/9/2011 Revision02 4 Circuit breakers

5. Magnetic Circuit Breakers Short circuit The fault current creates a strong magnetic field. This field forces the armature to move. This movement releases a spring, forcing the contacts to open. As this process is relatively quick, Magnetic Trip Action is best suited to SHORT CIRCUIT PROTECTION. 8/9/2011 Revision02 5

6. 8/9/2011 Revision02 6