Electrical generator or motor structure – Dynamoelectric – Rotary
Patent
1995-10-23
1998-01-13
LaBalle, Clayton E.
Electrical generator or motor structure
Dynamoelectric
Rotary
310103, 310 78, 310 92, 310118, 310166, H02K 1600, H02K 1602
Patent
active
057083142
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION
This invention concerns to a kind of A.C. electric drive device, including A.C. motors and the drive portions of machines using A.C. power. Said electric drive device includes a stator, a rotor and a transmission element called as the output element and used for driving the mechanical load. Said stator has a core for conducting magnetic flux, and a winding capable of generating a rotating or an alternating magnetic field when a suitable AC power is supplied. Said rotor, being in the rotating or alternating magnetic field, is capable of producing a torque at asynchronous speed. Said rotor drives the output element directly or through a transmission system with a fixed speed ratio.
The so-called "rotor capable of producing a torque at asynchronous speed" includes the "induction rotors" which can produce driving torque mainly depending on the electromagnetic effect of its induced current; the hysteresis rotor which can produce a torque mainly depending on the effect of magnetic hysteresis of its core material; and offer similar rotors, such as the rotors that have an integral steel core. While rotating under asynchronous speed in a rotational or an alternating magnetic field, the later type of rotor can produce a torque not only due to the electromagnetic effect of the induced eddy current but also due to the hysteresis effect of the steel material.
TECHNICAL BACKGROUND
Among existing electric drive devices used for driving the working machines, A.C. motors are the most commonly applied; among existing A.C. motors, the asynchronous motor, especially the type of "squirrel-cage" is the most extensively used. The asynchronous motors are simple in structure, reliable in operation, long in service life, low in cost, but small in starting torque and large in starting current, not large enough in overload capacity and has a rigid mechanical characteristic. This type of motors can normally be operated only in a narrow speed region. Therefore, conventional asynchronous motors and similar electric drive devices are not suitable for driving such machinery that must be working with a larger starting load, or of which the speed must be variable according to the load in a wider range.
These disadvantages of the asynchronous motor can be improved by increasing the resistance of its rotor winding. Having adopted this method it is able to limit the starting current and increase the starting torque to a certain degree, as well as soften its characteristics, but this method cannot increase the maximum torque and will significantly decrease the rated efficiency of the motor. Therefore, whenever the characteristics of the asynchronous motor and similar electric drive device cannot meet user's requirements, the more complicated motors, such as brush motors etc., will have to be used, even though these motors are either more expensive or shorter in service life and poorer in operating reliability.
DISCLOSURE OF THE INVENTION
In order to overcome the disadvantages of asynchronous motors and the similar electric drive devices, the purpose of this invention is to provide an A.C. electric drive device used as a prime driving unit or driving portion in some machines, which is reliable in operation, greater in starting torque and overload capacity, but not very complicated in structure and may drive the mechanical load effectively in a wider operation range.
In order to achieve this purpose, the electric drive device provided by this invention includes an electromagnetic portion and a transmission portion. Said electromagnetic portion includes a stator which can generate a rotating or an alternating magnetic field and, at least, two rotors capable of producing the driving torque under asynchronous speed. One of said rotors is called as the "main rotor", the other one the "auxiliary rotor". Said transmission portion has several transmission elements with fixed speed ratios between each other, including a transmission element which is called as the "output element" and used for driving the mechanical
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Enad Elvin G.
LaBalle Clayton E.
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