Introduction of eddy current
Introduction of eddy current
Operational Features Of
Eddy Current Brakes
How eddy current brake
Eddy currents are electric currents induced
in conductors when exposed to a changing magnetic field;
due to relative motion of the field source and conductor or
due to variations of the field with time.
This can cause a circulating flow of electrons, or current,
within the body of the conductor.
These circulating eddies of current have inductance and
thus induce magnetic fields.
Š Eddy current brakes, like conventional friction brakes, are
responsible for slowing an object, such as rotating machinery, a
moving train, or even a roller coaster.
These brakes make use of opposing tendency of eddy currents.
The drawbacks of ordinary brakes which uses mechanical
blocking could be eliminated by use of a more simple and
effective mechanism known as eddy current brakes.
Š There are two basic types:
COMPONENTS AND CONSTRUCTIONAL
FEATURES OF EDDY CURRENT
Cast Iron Core
Conducting (Copper) Wire
Mild steel machined from plates
Essentially the eddy current brake consists of two parts, a
stationary magnetic field system and a solid rotating part, which
include a metal disc.
Two members are separated by a short air gap, they're being no
contact between the two for the purpose of torque transmission.
Consequently there is no wear as in friction brake.
Stator consists of pole core, pole shoe, and field winding.
The field winding is wounded on the pole core.
Pole core and pole shoes are made of east steel laminations and
fixed to the state of frames by means of screw or bolts.
Copper and aluminum is used as winding materials.
During braking, the metal disc is exposed to a magnetic field from an
electromagnet, generating eddy currents in the disc. The magnetic
interaction between the applied field and the eddy currents slow down
the rotating disc. Thus the wheels of the vehicle also slow down since
the wheels are directly coupled to the disc of the eddy current brake,
thus producing smooth stopping motion.
HOW DOES AN EDDY CURRENT
BRAKE STOP SOMETHING MOVING?
Suppose we have a huge solid block of copper mounted on
wheels. It is moving at a very high speed and we need to stop it.
Suppose we place a giant magnet next to the track so that train
had to pass nearby.
As the copper approached the magnet eddy currents would be
generated inside the copper which would their own magnetic
As the front part approached the magnet eddy currents in that bit
of copper would try to generate a repulsive magnetic field to slow
down copper’s approach to magnet.
As the front passed by, slowing down, the currents there would
reverse, generating an attractive magnetic field that tried to pull the
train back again. (again, slowing it down).
The copper would heat up the eddy currents swirled inside
it, gaining the kinetic energy lost by the train as it slowed down.
Advantages Of Eddy Current Brakes:-
• It uses electromagnetic force and not mechanical friction
• Non-mechanical (no moving parts, no friction)
• Fully resettable
• Can be activated at will via electrical signal
• Low maintenance
• Operates at any rotational speed
• Light weight
• Eddy-current brakes are quiet, frictionless, and wear-free,
and require little or no maintenance.
• They produce no smell or pollution (unlike friction brakes,
which can release toxic chemicals into the environment).
All this makes them much more attractive than noisy friction brakes that need
regular inspection and routinely wear out. It's been estimated that switching
an electric train from friction brakes to eddy-current brakes could halve the
cost of brake operation and maintenance over its lifetime.
Braking force diminishes as speed diminishes with no ability to
hold the load in position at standstill.
That could be considered to be a safety issue, but it really means
that friction braking may need to be used as well.
Eddy-current brakes can only be used where the infrastructure
has been modified to accept them.
It can not be used at low speed vehicles or vehicle running at low
For additional safety on long decants in mountain area
For high speed passenger and goods vehicle.
Eddy current brakes are best substitutes for ordinary brakes, which
are being used nowadays in road vehicles even in trains, because of
their jerk-free operation.
In mountain areas where continuous braking force is needed, for a
long time, the eddy current braking is very much useful for working
Eddy current brakes are very much useful for high-speed
passengers and good vehicles.
It can also be used to slow down the trolleys of faster roller
There are a number of major commercial applications of eddy
current brake technology in the mining, railroad, and elevator
We'll also find eddy current brakes in all kinds of machines, such
as circular saws and other power equipment. And they're used in
things like rowing machines and gym machines to apply extra
resistance to the moving parts so your muscles have to work harder.
The ordinary brakes which are being used now a days stop the
vehicle by means of mechanical blocking. This may cause skidding
and wear and tear of the vehicle.
And if the speed of the vehicle is very high the brake could not
provide that much high braking force and it will cause problems.
These drawbacks can be eliminated by using a simple and effective
mechanism of braking system called eddy current brakes.
It is an abrasion free method for braking of vehicles including
It makes use of opposing tendency of eddy currents.