Electrical generator or motor structure – Dynamoelectric – Rotary
Patent
1993-09-22
1996-01-16
La Balle, Clayton E.
Electrical generator or motor structure
Dynamoelectric
Rotary
310261, 310180, 318701, H02K 1702, H02K 124, H02K 328, H02P 736
Patent
active
054850479
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a reluctance type motor which is used as a driving source for a drill machine, a compact driving source requiring high-speed rotation, and a large-output driving source requiring no precise control such as an electric car and a crane vehicle.
BACKGROUND ART
A reluctance type motor has so numerous disadvantages including vibration that few reluctance type motor has ever been practically utilized, although its output torque is large and no magnet rotor is required. Attaining both size reduction and speedup of motor rotation is very difficult to practically realize. Although rotational torque is obtained by magnetic attraction force acting between magnetic poles of the fixed armature and salient poles of the rotor, the magnetic attraction force is directed toward a center thereof. Thus, mechanical vibration is generated.
Such conventional motors require armature coils that are controlled by switching elements connected to both ends thereof for activating or deactivating these armature coils. Hence, expensive power elements increase in number and, therefore, the cost increases.
Furthermore, switching elements provided at a positive terminal side of an electric power source tend to be expensive as they require input electric signals supplied from another electric power source for controlling currents supplied to the armature coils.
A reluctance type motor has a rotor equipped with numerous salient poles and, therefore, its inductance is large. This increases magnetic energy amount stored into or discharged from magnetic poles or salient poles. And also increased is repetition frequency of such energy storage and discharge during one complete revolution of the rotor. It is, therefore, a problem that the reluctance type motor cannot rotate in a high-speed region nevertheless its large output torque. Also, it is another problem that the size of the reluctance type motor cannot be reduced due to a large number of salient poles.
Here, a low speed should be considered to be around 300 r.p.m and a high speed around 60 thousands rpm.
If compared with a DC motor having a magnet rotor, an extraordinary large inductance of the armature coil will cause a slow building-up of exciting current at an initial stage of the current supply period, as well as a slow trailing-edge at a terminating stage of the current supply period. The former will cause a smaller output torque, and the latter cause a counter torque.
In order to make building-up of armature current sharp in the initial stage of the current supply period, a voltage of an electric power source is increased. However, such building-up of the armature current will be too much sharp in a region after the magnetic saturation point. For this reason, the motor causes vibrations and electric noises. And, as above-described building-up section of the armature current corresponds to a section where the torque is small, only disadvantages will be enhanced. Thus, there is a problem such that a high-speed rotation cannot be realized due to the above-described torque reduction and counter torque. As the number of the salient poles is too much, magnetic energy is so numerous times transferred between armature coils. This increases iron loss. Accordingly, there is a problem that efficiency is lowered in a high-speed region.
If the applied voltage is increased in order to speed up the rotational speed, more than 600 volts will be required. This means no practical motor will be obtained.
If the building-up and trailing-edge of the armature current are sharpened in order to realize the speedup of the motor, iron loss will be correspondingly increased. It will be ideal to use a half-wave of sine waveform. This will not be easily obtained for some reasons.
Furthermore, salient poles of the rotor are generally required at least 4. Therefore, repetition frequency of energy storage and discharge during one complete revolution of the rotor will increase between the magnetic poles and the salient poles. Thus, efficiency is lowered and it bec
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Kabushikigaisha Sekogiken
La Balle Clayton E.
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