Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2000-05-05
2002-04-16
Mullins, Burton S. (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S074000, C310S152000, C310S153000, C310S154210, C310S254100, C310S261100
Reexamination Certificate
active
06373161
ABSTRACT:
BACKGROUND
The present invention is related to electric generators, devices that convert mechanical energy to electrical energy. More particularly, the present invention includes a rotor that contains a plurality of ferromagnetic sections imbedded in a non-magnetic medium and a stator containing both a plurality of magnets and conductor coils. Depending on the number of magnets and conductor coils in the stator, the number of magnetic sections in the rotor, alternating current (AC) electricity or direct current (DC) electricity is generated. The frequency of AC electricity generated is an integral multiple of the rotational frequency of the rotor and high frequencies can be attained.
Conventional electric generators rely on relative rotation between a magnetic field and electric conductor coils. The magnetic field may be stationary and the electric conductor coils revolve through it; or vice versa. To generate AC electricity with a frequency of 60 Hz, the rotor needs to rotate 60 cycles per second if the magnet has two poles or 30 cycles per second if two magnets have four poles. One method to increase the production of electrical energy from a generator is to increase the rotational speed of the rotor and then pass the resulting current through frequency and voltage controllers to adjust the frequency and voltage to standard values (e.g., 10 volts, 60 Hz). If a diesel or another type of engine is used to produce high rotational speeds, the engine may experience accelerated wear and tear, or there may be other damage. Also, in an electric generator, an average of two percent of the mechanical and electrical energy is converted to heat and consequently conventional high power generators require extensive and expensive heat removal systems.
The configuration in the present invention with stationary magnets and conductor coils has several advantages. One is that this configuration has simple and inexpensive construction, e.g. an external frame is not necessary. Another advantage is that it can be cooled simply and inexpensively by, for example, immersing both the conducting coils and magnets in cooling oil.
The present invention can also be used to produce DC electricity with a wide range of voltage and power without use of brushes, rectifiers, or commutators. Various types of DC generators have been disclosed in U.S. patents. U.S. Pat. No. 5,977,584 to Lin discloses a rotating machine that produces low voltage and power for applications such as recharging batteries and that whose function can be reversed to operate as a motor. U.S. Pat. No. 5,334,898 to Skybyk discloses high-density discoidal brushless induction open frame motor and generator with multistacking, multiphasing and multistaging capability. U.S. Pat. No. 5,278,470 to Neag discloses a homopolar machine that can produce high voltage DC electricity with limited power capability. U.S. Pat. No. 4,780,659 to Bansal and Krinickas discloses a high-power, high-voltage DC power supply containing a plurality of AC generators mounted on one rotator shaft, all AC generators being connected through multiple rectifier units.
DC generators found in the prior art tend to generate electricity in a conventional way and suffer from one or more of several disadvantages. The disadvantages include low voltage, low power, limited applications, complicated structure, expensive operational costs (including cooling costs), the need for rectifiers and filters, and the needs for high rotational speeds. As will be described later, the present invention provides a DC generator capable of producing a wide range of voltages and powers with a simple and inexpensive structure (commutators, brushes, and rectifiers are not used) and operations.
The present invention in an AC configuration produces AC electricity with frequencies that are integer multiples of the rotational speed of its rotor without the use of gears. Therefore, it is well suited for producing reliable electricity from energy sources that produce relatively slow rotation. One such energy source is wind energy. Usually, wind speed is too low to cause a wind turbine to rotate at even 10 cycles per second. Consequently, conventional wind generators use gears to increase the rotational speed of their rotors and pay the price in reduced efficiency. Other such sources are tidal energy, and low-head hydroelectric power in rivers. Electricity could be generated efficiently with the present invention from falls in rivers or from differences in elevations in tides as small as two meters in height. With use of multiple generators, the energy potential of low-head hydro can be used without the expense, and possible adverse environmental effects of building large dams. Also even a small generator could be energized by the flow of river current.
Accordingly, there are several objects and advantages of the present invention. One object is to provide an inexpensive electric generator of simple construction and with a simple cooling system. Another object is to provide an electric generator with a rotating magnetic field with a frequency of rotating much higher than the frequency of rotation of its mechanical rotor so that a wide range of power outputs and AC frequencies can be achieved. Another object is to provide an electric generator that can be built in different ways according to the availability of space, the types of current needed and the nature of the prime mover energy.
A further object is to provide an AC electric generator that can produce frequencies in excess of 10,000 Hz with a power output as high as available from conventional electric generators. A further objective of the present invention is to provide a simple and inexpensive DC electric generator capable of providing high power steady DC electricity or DC with minimal high frequency ripple and without use of commutators or brushes. A still further object is to provide a means of generating electricity from slow rotational motions associated with winds, tides, falling river water, and river current.
SUMMARY
The present invention achieves the above objectives by providing a rotating magnetic field with a frequency many times greater than the rotational frequency of its mechanical rotor because there is no relative mechanical movement between magnets and the electrical conductors. The invention includes a plurality of stationary units arrayed around a flywheel, or rotor, mounted on a rotating shaft energized by the prime mover. Each unit contains a magnet with a north pole and a south pole and a conducting coil. To reduce unnecessary magnetic flux, the magnets are oriented such that the north pole of one magnet is next to the north pole of one adjacent magnet and the south pole of the magnet is adjacent to the south pole of the other adjacent magnet (alternating orientation). The flywheel made of a non-ferromagnetic material with imbedded ferromagnetic material. In the primary embodiment of the invention, U-shaped magnets tapered to a sharp edge at the poles are used and the ferromagnetic material is in the form of bars imbedded in the periphery of the flywheel. The primary determinant of the character of the electricity produced are: (1) the relationship between the number of magnets and the number of ferromagnetic sections; and (2) the positioning of the magnets.
There is an air gap between the poles of magnets and the ferromagnetic sections. The width of the air gap depends on the angle of rotation of the flywheel relative to the stationary magnets. Each time, a ferromagnetic bar passes the poles of a magnet in the primary embodiment, the air gap passes from a maximum to a minimum and back to a maximum to produce one half of an electric cycle. When the air gap is decreasing, magnetic flux increases in the circuit of the magnet and when the air gap is increasing, the magnetic flux decreases. Hence for every two ferromagnetic bars that pass the poles of a magnet, one complete cycle of the magnetic flux results, which induces one complete cycle of electro motive force (EMF) in the conductor coils wound about the magnets. For a DC ge
Kier Philip H.
Mullins Burton S.
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