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An eddy current brake is a type of braking mechanism that is typically used for trains and roller coasters. This braking mechanism utilizes a process of electromagnetic induction to create a phenomenon known as eddy currents. These eddy currents create heat-producing resistance, which is used to provide braking power for a vehicle. During the braking process, an electromagnet exposes the metal wheels of a train to a magnetic field which generates eddy currents in the moving wheels. The interaction between the magnetic field and the eddy currents it produces causes the wheels to encounter enough resistance to reduce the train’s speed. The resistance produced by an eddy current brake increases at higher speeds and decreases at slower speeds to produce a gradual braking effect.
Eddy current braking mechanisms used for trains do not become worn over time because they never make physical contact with the rails. Although this type of brake is ineffective at lower speeds, it is very reliable at higher speeds for both regular and emergency braking. This type of braking system can be either rotational or linear. A rotational eddy current brake operates in the same way as an electric motor, with a spinning rotor and stationary coil used to provide the resistance needed for braking power. Linear versions of these brakes create a magnetic field around the rails that the train rides upon to provide resistance for braking.
Regenerative brakes are similar to eddy current brakes, but differ significantly in the way they use energy. All of the energy used in this type of brake system is lost during the actual braking process. Regenerative brakes not only use the motion of the wheels to generate energy during braking maneuvers; they also use this motion to recover energy that is generated when the train is not braking. This recovered energy can be stored for later use or used at the same time that it is produced.
Roller coasters sometimes use a linear version of the eddy current brake to stop the vehicle at the end of the ride. The most common configuration utilizes thick copper plates attached to the sides of the roller coaster. When the vehicle reaches the end of its run, these plates pass between a set of strong magnets permanently attached to the rails of the track. As the plates pass between the magnetic field, resistance is created causing a braking effect to occur. A mechanism similar to an eddy current brake is used in certain types of power tools such as drills and circular saws to quickly bring moving parts to a halt.
A lot of heavy machinery or transport vehicles, like locomotives, use a fail safe system called a dead man's switch.
A dead man's switch is a switch that stops a piece of machinery or vehicle automatically if it is in danger of causing significant danger. The switch is engaged if there is no response from an engineer or operator, assuming that the responsible party is incapacitated. There are some switches that can be engaged from an outside source as well.
It is called a dead man's switch because the fear that the death of an operator could leave a machine or vehicle unmanned.
Dead man's switches have even made there way into many people's back yards as well. The button on that chain saw that unlocks the trigger for you to turn the saw on, that is a form of dead man's switch.