Electricity: motor control systems – Closed loop speed control system for dc motor with commutator
Reexamination Certificate
2001-10-24
2004-04-13
Masih, Karen (Department: 2837)
Electricity: motor control systems
Closed loop speed control system for dc motor with commutator
C388S806000, C388S807000, C388S928100
Reexamination Certificate
active
06721496
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to permanent magnet, shunt, series, and compound direct current motors. More particularly, the present invention relates to enhancing the efficiency of direct current electrical motors by using electrical resonance circuitry.
BACKGROUND OF THE INVENTION
Electrical motors are rated by their efficiency. Efficiency is simply the quotient of the mechanical power output, divided by the electrical power input.
Efficiency
=
Mechanical
power
output
Electrical
power
input
To get a percent efficiency, the quotient is simply multiplied by 100.
Percent
Efficiency
=
(
100
)
×
Mechanical
power
output
Electrical
power
input
High efficiency motors that are on the market today, usually operate with efficiency maximums of about 97%. However, there are motors that have higher efficiencies. U.S. patents have been issued for devices that claim to approach efficiencies of 100%.
Since electric motors are used by the hundreds of millions in a myriad of applications even slight improvements in the efficiencies of electric motors save an enormous amount of electrical energy. Since much of this energy is generated from fossil fuels, increases in the efficiencies of electric motors have considerable positive environmental impacts.
Using electrical resonant circuits to drive or otherwise control electric motors is known, however these arrangements have drawbacks such as using a mandatory permanent magnet in the rotor and stator, which have fluxes that are alternatively shorted out and added to by a separate electromagnets in the rotor and stator; powering the motor with a DC battery, and having to adjust the motor's load or the capacitors to keep the machine at proper resonance.
Other prior art arrangements use brushless DC motors that have permanent magnets as rotors and use a LC resonant oscillator to constantly change the magnetic polarities of the stator poles in order to keep the rotor moving with the LC resonant oscillator alternatively switched on and off.
The prior art also includes single phase AC motors powered by parallel resonant circuits, and resonant series circuits as well as polyphase AC motors powered by quasi-parallel and series resonant circuits and by quasi-parallel and series resonant circuits.
SUMMARY OF THE INVENTION
The present invention is directed to an arrangement for powering a DC motor with an AC source comprising a parallel resonant tank circuit connected to the AC source, the parallel resonant tank circuit having a capacitive branch and an inductive branch connected in parallel to generate a resonanting tank current. A rectifier is connected to the parallel resonant circuit to transform the AC voltage to DC voltage, and the DC motor has its armature and if desired its stator, connected to the rectifier to receive DC voltage therefrom.
In further aspects of the invention, the rectifier of the parallel resonant tank circuit is a full wave rectifier electrically connected in series with one of the two branches of the parallel resonant tank circuit. In addition, the parallel resonant tank circuit contains an optional voltage balancing circuit electrically connected in series with one of the branches of the circuit opposite to that in which the full wave rectifier is located, the voltage balancing circuit having a voltage drop thereacross substantially equaling the voltage drop across the full wave rectifier.
In still a further aspect of the invention, the DC output of the full wave rectifier is electrically connected to the DC motor with a variable DC voltage between the full wave rectifier and a connection to the input terminals of the DC motor so as to automatically vary the DC voltage to minimize the influence of back emf of the DC motor.
In further aspects of the invention, a secondary armature is on the rotating shaft of the DC motor, the secondary armature having an armature core which has the same number of windings as a first armature, each secondary armature winding being dedicated to the removal of the AC voltage on one main armature winding to minimize back emf. And in still a further aspect of the invention, a secondary stator is disposed around the secondary armature, the secondary stator having as many stator windings as a first stator first.
In an additional aspect of the invention, a bank of transformers is positioned on the shaft of the DC motor, each transformer having a primary winding and secondary winding, the number of transformers being equal to the number of secondary armature windings with each transformer being dedicated to one secondary armature winding, and therefore dedicated to one main armature winding.
In an additional aspect of the invention, a rotor speed detection means constantly monitors the rotor speed of the DC motor and sends a signal representative of the rotor speed to an electronic apparatus which computes the needed value of a variable DC source element or a variable DC motor element, and sends out a signal that varies this adjustable element to minimize back emf.
According to additional aspects of the invention, current flowing through the brush, the commutator, the armature winding, and the stator winding is varied by varying the voltage of the AC source and speed and torque is varied by varying the voltage of the AC source and/or the magnetic field intensity of the stator windings.
DEFINITIONS
(1) DC means direct current and voltage. The current normally flows in one direction, and the voltage normally has one polarity. The opposite of AC.
(2) AC means alternating current and voltage. The current normally and rhythmically alternates direction of travel, and the voltage normally and rhythmically alternates polarity. The opposite of DC.
REFERENCES:
patent: 4064442 (1977-12-01), Garron
patent: 4167691 (1979-09-01), Sorensen et al.
patent: 4406002 (1983-09-01), Wine
patent: 4675565 (1987-06-01), Lewus
patent: 4734601 (1988-03-01), Lewus
patent: 4772814 (1988-09-01), Lewus
patent: 4794288 (1988-12-01), Lewus
patent: 4808868 (1989-02-01), Roberts
patent: 4959573 (1990-09-01), Roberts
patent: 6545443 (2003-04-01), Kushida
Masih Karen
Millen White Zelano & Branigan P.C.
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