Electricity: motive power systems – Induction motor systems – Primary circuit control
Reexamination Certificate
1999-07-08
2001-01-16
Ip, Paul (Department: 2837)
Electricity: motive power systems
Induction motor systems
Primary circuit control
C318S775000, C318S777000, C310S179000, C310S180000
Reexamination Certificate
active
06175209
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention generally relates to permanent-split capacitor motors and, in particular, to a 2-pole/4-pole motor having a shared main winding and a shared auxiliary winding between the 2-pole configuration and the 4-pole configuration.
2. Description of the Prior Art
PSC motors, as one kind of single-phase induction motors, come in various multiple configurations and various pole configurations. One common configuration is a 2-pole/4-pole motor which operates at about 3,600 rpm at 60 Hz in the 2-pole configuration and which operates at about 1,800 rpm at 60 Hz in the 4-pole configuration. Such motors are often used as part of a hermetically sealed compressor to drive the compressor at two speeds, both a low speed and a high speed, to provide efficient compressor operation.
Within the limited space of the compressor, to provide the highest motor efficiency for a certain output power, one needs to make the best use of the active material, i.e., copper and steel. Sharing windings between 2-pole and 4-pole configurations is an important approach to achieve this. However, in the past, it has been believed that 2-pole/4-pole PSC motors can only share a main winding between the 2-pole and 4-pole configurations. It was believed that 2-pole/4-pole motors could not share both the main and auxiliary winding at the same time because it could not keep the phase shift between the main and auxiliary windings equal to 90° for both the 2-pole and 4-pole configurations. In particular, if both main and auxiliary windings are shared and the auxiliary winding has 90° phase shift with the main winding in the 2-pole mode, the phase shift in 4-pole mode becomes 180°. If the auxiliary winding has a 90° phase shift with the main winding in the 4-pole mode, the phase shift in 2-pole becomes 45°. When a phase shift between the main and auxiliary windings is equal to 180°, the motor cannot start. When a phase shift is equal to 45°, the motor performance is generally poor. Therefore, the prior art has generally employed a separate auxiliary winding in each configuration for a PSC motor having 2-pole and 4-pole operating modes or configurations, to keep the phase shifts between the main and auxiliary windings both equal to 90°.
Therefore, there is a need for a 2-pole/4-pole PSC single phase motor with a shared main winding which also has a shared auxiliary winding.
SUMMARY OF THE INVENTION
To share both main and auxiliary windings for 2-pole and 4-pole modes, the invention employs a new winding configuration. In this new configuration, after a simple reconnection, the 2-pole mode has 125° phase shift and the 4-pole mode has 70° phase shift for a 36-slot stator. Both 2-pole and 4-pole modes achieve very good performance with these phase shifts. According to the prior art, the best phase shift between the main and auxiliary windings is a little more than 90°, e.g., about 105°. Therefore, as compared with 90°, both 70° and 125° result in a slightly reduced performance in certain respects. However, since the auxiliary winding has been shared, for the same material cost, the overall performance of this 2-pole and 4-pole motor is substantially better than the design based on the prior art.
It is an object of this invention to provide a 2-pole/4-pole PSC motor having a shared main winding and a shared auxiliary winding; such a motor which has a reduced winding material requirement so that the cost of manufacturing the motor is reduced; such a motor which has efficient operation; such a motor which can be manufactured without significant retooling or redesign; such a motor which employs a single capacitor for both the 2-pole and 4-pole configurations.
In one form, the invention is a motor comprising: a stator core; a rotor in rotational relationship with the stator core; a shared main winding on the core having 2-pole and 4-pole configurations; a shared auxiliary winding on the core having 2-pole and 4-pole configurations; and a switching circuit for selectively simultaneously energizing the shared main winding and the shared auxiliary winding in 2-pole and 4-pole configurations.
In another form, the invention is a motor having a 2-pole configuration and a 4-pole configuration and comprising a stator core; a rotor in rotational relationship with the stator core; a shared main winding on the core; a shared auxiliary winding on the core; and a switching circuit. The shared main winding, when energized in the 2-pole configuration, generates a first main magnetic field and, when energized in the 4-pole configuration, generates a second main magnetic field different from the first main magnetic field. The shared auxiliary winding on the core, when energized in the 2-pole configuration, generates a first auxiliary magnetic field and, when energized in the 4-pole configuration, generates a second auxiliary magnetic field different from the first auxiliary magnetic field. The switching circuit selectively energizes the shared main winding and the shared auxiliary winding in the 2-pole configuration and selectively energizes the shared main winding and the shared auxiliary winding in the 4-pole configuration.
The invention also includes a method of making a motor comprising the steps of:
providing a stator core;
providing a rotor in rotational relationship with the stator core;
winding a shared main winding on the core having 2-pole and 4-pole configurations; and
winding a shared auxiliary winding on the core having 2-pole and 4-pole configurations.
Other objects and features will be in part apparent and in part pointed out hereinafter.
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Fei et al., “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.
Emerson Electric Co.
Ip Paul
Senniger Powers Leavitt & Roedel
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