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hello!!! iam a final year student doing my B Tech. Electrical and Electronics. I am in need of the report for the topic Electromagnetic Brakes. Kindly help me and mail me the above said as soon as possible. I'll try my best to upload topics and reports in this forum. Thanks in advance.
sunanda lal
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Presented by:
Sachin
Faruque
Rakesh
[attachment=13623]
ELECTROMAGNETIC BRAKES
LIMITATION OF CONVENTIONAL FRICTION BRAKES
Friction between contact surfaces leads to generation of
heat that causes temperature increase of components.
(consequences- fading and disk warping)
Wear and tear of friction lining
during braking.
Less accuracy of applied braking
torque.
Performance reduction is more
with passage of time.
Require more maintenance.
Take large space and have greater
weight.
It becomes self locking if properly not designed.
motivation
The brake imposes controlled deceleration at variable speeds.
Braking system having smooth response, thereby eliminating shock loading and extending equipment life.
No physical contact between rotating and stationary members.
Produce required braking torque within given constraints and parameters
Objective
To demonstrate the production of torque, we will essentially take the driveshaft and build a test rig around it. By attaching a conductive disc to the driveshaft and setting up electromagnets around it, we can create a braking force (assuming the disc is moving fast) to decelerate the driveshaft. If we can prove that the required torque is achievable via eddy-current-braking, then the electro-magnets can be installed.
LAWS OF ELECTROMAGNETISM
FARADAY’S LAW : The induced electromotive force(emf) in any closed circuit is equal to the time rate of change of the magnetic flux through the circuit.
AMPERE CIRCUITAL LAW : It relates the integrated magnetic field around a closed loop to the electric current passing through the loop.
LORENTZ FORCE: It is the force on a point charge due to electromagnetic fields. F= I (L X B)
LENZ’S LAW : An induced current is always in such a direction as to oppose the motion or change causing it.
FUNDAMENTAL physics of eddy-current braking
Conductor moves across a magnetic field(Electromagnet)
Electric field will be produced due to time varying magnetic flux
Eddy currents generated due to electric field
These currents exert an opposing force on conductor
Eddy Current Brake Rationale
Advantages
Non-mechanical (no moving parts, no friction)
Contactless braking and absence of maintenance
Fully resettable, no parts need be replaced
Can be activated at will via electrical signal
Operates at any rotational speed
Reduced sensitivity to high temperatures
Relative ease of control
Limitations
Requirement for a large excitation current
Lack of failure safety
The excitation current is necessarily supplied at a low voltage, which induces high ohmic losses in conductors, diminished bus voltage, and renders electronic control challenging.
Heavy wiring from the battery to the retarder, heating of the coils
BRAKE DESIGN PARAMETERS
Motor characteristics:
PARAMETER VALUE
Nominal armature voltage 180 V
Nominal armature current 14 A
Armature resistance 1.43 Ω
Maximum speed 1440 rpm
Nominal shaft power 1 hp
Maximum torque 4.94 N.m
Torque constant 0..352 N.m/A
CALCULATED DESIGN VALUE
electromagnet residual flux density Br 0.4 T
Reluctance of core and air gap L 3.22x10e7 AT/Wb
Magnetic flux intensity ø 0.0133 milliweber
Electromotive force required MMF 430 AT
Number of turns of coils N 145
Current applied to electromagnet I 3 A
