Destruction for Good

Destruction! Blow Up! Eliminate! These are not pleasant words!Unfortunately, when it comes to safety we have no other choices. In the electrical industry, fuses are destroyed in order to protect lives or property.Whenever there is a big fault in the power lines, possibly caused by short-circuiting, fuses are very helpful to stop the flow of current.Unlike circuit breakers, fuses have no mechanical moving parts that can fail to operate. A fuse is just an electrical link in the circuit that can melt very quickly whenever a certain temperature is reached.Fuses have 4 things to do in a circuit:1. They must sense faults2. They must open quickly when a short-circuit occurs3. They must also sense the normal overloaded conditions, but must open if the overload becomes excessive or prolonged.4. They must not change or alter the characteristic of the current during normal operation.Early types of fuses use lead wires, selected based on their diameters, connected to terminals. These types have some disadvantages. Whenever a fuse blows, the molten metal spatters over the equipment and could cause injury to people or cause fires, especially when the arc was not confined.Later, cartridge fuses replaced the old lead wire fuses. These consist of non-conducting cylinders which contain soft metal fuse strips. The strips are connected to the ends of the cylinders by metal caps or ferrules. The entire cartridge fuse is mounted onto a matching fuse block.Even these cartridge fuses have 2 types - those with renewable fuse links and those one-time non-renewable types. The only advantage of the renewable type - they are more economical because the cartridge can be reused. However, more precautions are needed with regards to the cleanliness of the contacts, the securing of the cap bolts, and the choice of the current rating of the link.Whenever a fuse blows, it means there is already a big fault in the circuit. Electricians must be especially careful during this time and take the necessary precautions. The fuses blow up for safety. Don't cause another blow up!Until next time...Are You Stumped by Complicated Electrical Calculations?Learn Electro-Technology Calculations for 1st Class Marine Engineers Competency License Exams at Electro-Technology Questions & Answers e-book. Applicable for all electrical installations both on ships and at shore. http://www.free-marine.com/et.htm