Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1997-05-13
2001-05-15
Tamai, Karl I. E. (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S194000, C310S181000
Reexamination Certificate
active
06232693
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to variable or switched reluctance motors (“switched reluctance motors”), and more particularly to improvements in switched reluctance motors that reduce noise, enhance the positioning of the rotor and stator poles, and facilitate the assembly of pre-wound and wound-in-place coils to adjacent stator poles.
BACKGROUND OF THE INVENTION
Switched reluctance motors have been used for years in a number of applications because they are generally more economical to run than other types of motors, such as brushless permanent magnet motors. This is due, in part, to the design of switched reluctance motors which have poles on both the rotor and stator, and phase windings only on the stator. Switched reluctance motors are generally more expensive than other types of less sophisticated motors, however, because they employ electronic circuitry for controlling the current in each of the motor phases. Although, with the cost of electronic circuitry reducing, switch reluctance motors are becoming more cost competitive. In fact, switch reluctance motors have recently been chosen over other types of motors for a number of applications. This is particularly the case in direct drive applications where the need for complicated gear trains is eliminated.
Known switched reluctance motors have several drawbacks and are still in need of improvement. For example, switched reluctance motors can make a siren noise that is caused by the interaction of the rotor and stator pole tips and the cavity spaces between the poles as the rotor turns inside the stator. Also, for single phase switched reluctance motors, unless the rotor and stator poles are properly aligned when the motor comes to rest, consistent motor start-up is not possible. In some positions, the motor will not even start. One solution to this later problem is to install permanent magnets in the stator assembly adjacent to the stator poles. A drawback with this solution, however, is that there is no quick, easy and economical technique for installing the permanent magnets within the coil windings.
The present invention seeks to eliminate or at least minimize some of these drawbacks.
SUMMARY OF THE INVENTION
In one aspect of the present invention, an improved switched reluctance motor is provided. The switched reluctance motor according to the present invention includes a rotor and a stator. The stator preferably has four equally spaced stator poles each having an inner curvilinear face, which is generally aligned with the curvilinear faces of adjacent stator poles in a circumferential path. A stator insert or mounting element is also provided that extends between adjacently spaced stator poles of the stator. Each stator insert has a curvilinear face that is generally aligned in the same circumferential path as the curvilinear faces of the adjacently spaced stator poles so as to reduce siren noise. Some of the stator inserts are also constructed to include at least one pocket opposite its curvilinear face for receiving a magnet that facilitates positioning of the rotor relative to the stator poles. In particular, the magnet functions to “park” the rotor in a position that allows for efficient motor start up. The stator insert is further provided with spaced and generally oppositely extending arms for receiving and mounting either pre-wound stator coils or for receiving coils wound in place.
In another aspect of the present invention, a method for assembling a pre-wound coil relative to adjacently spaced stator poles is provided. In the preferred method, a mounting element, such as the stator insert, is installed between adjacently spaced stator poles. The pre-wound coil is then secured to the adjacently spaced stator poles and spaced arms of the mounting element. The pre-wound coil is placed around two adjacent stator poles and secured to the mounting element by hanging it on a hook portion of the mounting element on one side and fastening it to a strut portion of the mounting element on the other. Alternatively, the coils can be directly wound over two adjacent stator poles and secured behind hooks in the inserts which are installed between the adjacent stator poles.
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Cox Karmen D.
Gierer Joseph T.
Hendrix George E.
Emerson Electric Co.
Howrey Simon Arnold & White , LLP
Tamai Karl I. E.
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