QUES. Describe briefly the working of following:
(a) Magnetic cranes
(b) Fuse
(c) MCB
Answers
Answer:
magnetic cranes-
These large cranes are used to pick up and move metals containing things such as steel and iron, which is primarily found in recycling plants and junk yards. The electromagnetic cranes work by using a magnetic field that is created by an electric current that can be turned off and on whenever it is necessary. The electromagnet consists of an iron middle with a wire wrapped around it, which is where the electric current travels.
b)fuse
A fuse is a simple and highly effective way to protect a device from dangerous levels of current:
Current flowing through a conductor’s nonzero resistance leads to power dissipation.
Power is dissipated in the form of heat.
Heat raises the temperature of the conductor.
If the combination of current amplitude and duration is sufficient to raise the temperature above the fuse’s melting point, the fuse becomes an open circuit and current flow ceases.
Though the fundamental operation of a fuse is not complicated, there are subtle points to keep in mind. The rest of this article will help you to understand some important details related to the behavior and use of fuses.
c) MCB(miniature circuit breaker)-
Whenever continuous overcurrent flows through MCB, the bimetallic strip is heated and deflects by bending. This deflection of bi-metallic strip releases a mechanical latch. As this mechanical latch is attached with the operating mechanism, it causes to open the miniature circuit breaker contacts, and the MCB turns off thereby stopping the current to flow in the circuit. To restart the flow of current the MCB must be manually turned ON. This mechanism protects from the faults arising due to overcurrent or overload. But during short circuit condition, the current rises suddenly, causing electromechanical displacement of plunger associated with a tripping coil or solenoid. The plunger strikes the trip lever causing immediate release of latch mechanism consequently open the circuit breaker contacts. This was a simple explanation of a miniature circuit breaker working principle.