Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1998-06-04
2001-07-03
Ponomarenko, Nick (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S198000, C318S772000, C318S774000, C318S776000
Reexamination Certificate
active
06255755
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a single phase three-speed induction motor, and in particular to such a motor in which a substantial portion of the windings are shared for operation at different speeds.
BACKGROUND OF THE INVENTION
Multispeed pole-changing single phase motors typically comprise separate windings for operation at each speed. For example, in the case of a three speed induction motor, the stator might include an eight-pole main winding for operation at low speed, a six-pole main winding for operation at medium speed, and a four-pole main winding for operation at high speed. A separate auxiliary winding is often provided for starting the motor. This auxiliary winding is typically a four-pole winding for so-called “hard” starting. In these motors, only a small portion of the windings, the coils under one pole are shared for operation at different speeds. The application of different approaches for winding sharing in the prior art is limited by complicated reconnection which substantially increases the motor cost.
To accommodate a large number of windings in the limited slot size the windings typically are made of copper, which is relatively expensive.
SUMMARY OF TIE INVENTION
The present invention relates to a three speed, pole changing single phase capacitor-start or split phase induction motor in which a substantial portion of the windings for the various speeds are shared through a simple winding reconnection. This leaves more room in the slots, and allows bulkier but less expensive materials (such as aluminum) to be used for the windings. More particularly, the motor of the present invention comprises a stator, and a rotor rotatably mounted within the stator. The stator comprises a core, which is conventionally made of a stack plurality of laminations of a magnetically permeable material. The core has a plurality of slots therein for receiving the windings. According to the present invention, these windings include a first winding, having four coil sections; a second winding having two coil sections; a third winding having two coil sections; a fourth winding having six coil sections; and an auxiliary starting winding having six coil sections.
Shared winding techniques have been proposed before. However, the feasibility of such techniques largely depends on the simplicity of the winding reconnection. The winding configuration of the present invention used the existing starting switch and requires only one additional single pole, single throw contact from a switch outside the motor, such as a timer, relay, electronic switch, etc. As compared with separate winding motors this is very easy and inexpensive to implement.
The windings are connectable to operate in a four pole high speed configuration, a six pole medium speed configuration, and an eight pole low speed configuration. More particularly the first winding, the second winding, and the third winding are arranged in the slots so that they can be connected to operate in a four pole conventional configuration. The second winding and the third winding are also arranged in the slots so that they can be connected to operate in an eight pole consequent configuration. The fourth winding is arranged in the slots so that it can be connected to operate in a six pole conventional configuration. Lastly, the auxiliary winding is arranged in the slots so that it can be operated in a six pole conventional configuration during start-up of the motor.
Because in this preferred embodiment the windings for eight pole operation are fully shared with the windings for four pole operation, there is extra room in the stator slots. This allows a bulkier but lighter material, such as aluminum, to be used for the windings instead of a more compact but heavier materials such as copper. Thus the resultant motor is significantly lighter, not just because of the elimination of a separate winding for operation in the eight pole-mode, but because the space freed up by the elimination of the separate eight pole winding allows a lighter material to be used for the remaining windings. Furthermore, aluminum is considerably less expensive than copper, so the motor is less expensive to manufacture.
These and other features and advantages will be in part apparent, and in part pointed out hereinafter.
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Design and Test Analysis of Single-Phase Induction Motors with 4-8 Pole Common Winding IEEE Transactions on Industry Applications, vol. 31, No. 6 Nov./Dec. 1995; pp. 1-5.
Dinh Le Dang
Ponomarenko Nick
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