Electricity: motive power systems – Braking
Reexamination Certificate
2000-10-20
2002-11-19
Fletcher, Marlon T. (Department: 2837)
Electricity: motive power systems
Braking
C318S375000, C318S381000
Reexamination Certificate
active
06483268
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a DC motor brake system, and more particularly of the type that uses a solid state switching to short the motor.
2. Description of the Related Art
Many designs for DC motor brakes have been designed in the past. Current art discusses a switch being used to place a “short circuit” across a turning/rotating DC motor. The kinetic needs to be dissipated for the rotating motor to stop. A rotating DC motor acts as a DC generator and the short circuit is applied to “brake” the “motor/generator”. Driving a generator into a “short circuit” develops an infinite current (I=E/0=dividing “some voltage” by zero). In this case where we are applying a short circuit, current equals voltage divided by almost zero resistance of the active switching element and internal impedance of the motor generator. This, abruptly stops the motor/generator since “infinite current requires infinite torque”, and is therefore unattainable. In the present invention a very low resistance is applied to brake the motor/generator and current is thus correspondingly high.
The brakes used for D.C. motors in the past typically include a mechanical switch element. Several problems can arise since the mechanical switch cannot “switch in zero time”. The mechanical switch also exhibits some mechanical “contact bounce” and thus the generator does not see a resistance of “zero ohms” continuously. Braking action is adversely affected by some inconsistencies in switching time, contact arcing/welding of switch contacts by the high currents generated and the switch contacts and associated circuit resistances are not zero ohms. Therefore, the current is limited.
SUMMARY OF THE INVENTION
It is one of the main objects of the present invention to provide an electronic brake system for D.C. motors that eliminates the problems found with those that use mechanical components, including switch contact bouncing.
It is another object of this invention to provide an electronic brake system that allows a D.C. motor to coast to a stop irrespective of whether the power is lost.
It is still another object of the present invention to provide a very fast switching electronic brake.
It is yet another object of this invention to provide such a device that is inexpensive to manufacture and maintain while retaining its effectiveness.
Further objects of the invention will be brought out in the following part of the specification, wherein detailed description is for the purpose of fully disclosing the invention without placing limitations thereon.
REFERENCES:
patent: 3660738 (1972-05-01), Anderson et al.
patent: 5712549 (1998-01-01), Engel
patent: 5764009 (1998-06-01), Fukaya et al.
patent: 5847522 (1998-12-01), Barba
patent: 6373207 (2002-04-01), Yablonovitch
Bordas A.
Sanchelima J.
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