Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1998-09-28
2001-01-30
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S216006, C310S216055, C310S254100, C310S166000
Reexamination Certificate
active
06181041
ABSTRACT:
BACKGROUND OF THE INVENTION
a) Field of the Invention
The present invention relates to an inductance rotating electric machine used as motors or generators.
b) Description of the Related Art
Generally, a rotating electric machine that needs sine waveform magnetic field in an air gap portion employs a distributed winding as a winding method. For example, in an inductance motor illustrated in
FIGS. 18 and 19
, a stator S is arranged to surround an outer circumference of a rotor R, and core portions SC
1
that extend radially in a rib-shape are formed at a laminated core of an armature constituting the stator S. A coil SL is superposed shifting slot SC
2
created between the radial rib-like core portions. This method in which the coil SL is superposed shifting the slots, however, makes it difficult to wind the coil and also requires longer winding. Thus, the winding height H
1
may be higher.
Global environmental issues have become serious recently, requiring energy-saving and power-saving as a first priority. Environmental issues are especially dominated by the issue of power consumption, and motors consume more than half of the available power. For this reason, it is very important to increase motor efficiency and decrease loss (of power) as much as possible. Also, the same consideration is given to generators that generate electric power.
OBJECT AND SUMMARY OF THE INVENTION
A primary object of the present invention is to provide an inductance rotating electric machine in which the efficiency value is greatly improved by, for a high property, modifying an armature that has a winding at a core winding portion thereof.
The present invention relates to a property-improved structure of the rotating electric machines including motors and generators. Motors convert electrical energy to mechanical energy; generators convert mechanical energy to electrical energy. Therefore, motors and generators are basically the same in structure and configuration. It is, therefore, possible to use a motor as a generator, and vice versa. For this reason, all the following description will be referred to a motor.
Generally, output and torque are used as an index of the motor's property. However, the motor's property cannot be expressed in an absolute value by the above indices because the output and torque vary depending on applied voltage, the number of windings, radiating condition, design, etc. The efficiency value is another index of the motor's property which properly expresses the relationship between the output and the loss. However, efficiency value also varies depending on loads or the number of rotations, and therefore, with the initial zero output, the efficiency value is also zero. This also cannot be an absolute index to express the motor's property.
To improve the efficiency value of a motor, it is a basic to understand what the motor's property is, what the efficiency is, and how they are determined. As a result of studies done by the present inventor, the following was understood.
The absolute index of the motor's property is a proportional constant that expresses (determines) the relationship between the torque generated and the loss (copper loss) caused. In an inductance motor, the proportional constant equals torque/copper loss. In other words, the proportional constant that expresses the relationship between the torque and the copper loss caused when the current is applied never changes even when the applied voltage, the number of windings (with the same space factor), and the load condition are changed. Thus, it is understood that this proportional constant is an absolute index that expresses the motor's property.
Also, the efficiency value is output/input=output/(output+loss), where the output is the number of rotations x torque, the number of rotations can be expressed by the applied voltage and the loss, and the loss mainly means the copper loss. Therefore, it is understood that the efficiency value is mostly determined by the proportional constant.
To enhance the motor's property (to increase the efficiency), various attempts have been made, such as making large motors and increasing the space factor of the winding. However, the motor's property is enhanced by changing the condition of factors that determine the proportional constant.
Next described are the reasons why this proportional constant value determines the absolute index of the motor's property and the factors that determine this proportional constant value.
The magnitude of the motor torque depends on the amount of the change in magnetic energy caused by relative move between the primary and secondary sides (currents) which are placed opposite one another. There are two kinds of magnetic energies: one generated and retained by a self-inductance L between the primary and secondary sides (currents); the other generated and retained by a mutual-inductance M between the primary and secondary sides (currents). Which magnetic energy is used for driving depends on the type and structure of the motor. Inductance motors use the magnetic energy caused by M.
When the configuration such as the number of magnet poles is set, the magnitude of the torque generated at primary and secondary currents I
1
and I
2
is mostly determined by the maximum value of the magnetic energy, that is, the magnitude of the mutual-inductance M in inductance motors. The magnitude of the magnetic energy generated by the mutual-inductance M is expressed by M×I
1
×I
2
. In inductance motors, the first current I
1
, is proportional to the secondary current I
2
. Therefore, the magnetic energy can be expressed by M×I
1
×I
2
=M×current I
2
. I
2
where I represents the total current.
Since the copper loss is a resistance loss, it can be expressed by R×I
2
. Therefore, the proportional constant that determines the relationship between the torque and the copper loss is torque/copper loss. Consequently, the proportional constant can be expressed by M/R.
Considered next are the factors that determine the mutual-inductance M and copper loss (resistance loss) R. Eliminating the factor, the number of winding turns of coil, which affects equally M and R, M can be mainly expressed by the primary-secondary facing surface S and the air gap length, g. R is mainly determined by a coil cross-sectional surface A and the coil length, I, per winding turn. Considering that the air gap length, g, is mostly fixed, the above mentioned proportional constant can be expressed by only main components as follows:
S×A/I=S/coil component
It is understood that improving the main components constituting the proportional constant to increase the proportional constant value enhances the motor s property, resulting in improving the efficiency value.
Observing the proportional constant in conventional products, one finds that conventional inductance machines have a drawback. In other words, the common factor to determine the numerator of the formula for the proportional constant is the primary-secondary magnetic facing surface S. The more the facing surface S is enlarged, the higher the proportional constant and efficiency value become.
It is understood, however, from the example of the three-phase inductance motor (see
FIG. 18
) which is a typical rotating electric machine, that the ratio of the height H
3
of the primary-secondary magnetic-facing portion with respect to the entire motor height H
2
in the axial direction is extremely small. This is because, as described before, the winding height H
1
occupies much of the axial space. As a result, the above mentioned magnetic-facing surface S is extremely small.
If, without changing the condition of the coil component, the magneticfacing surface can fill the axial motor space fully, the above mentioned proportional constant can be greatly improved. This can easily reduce the loss in the same torque (or output) to {fraction (1/2 )} or ⅓, for example.
This condition is possibly created depending on the structure.
Mullins Burt
Ramirez Nestor
Reed Smith LLP
Sankyo Seiki Mfg. Co. Ltd.
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