Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1999-09-21
2001-11-27
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S184000, C310S049030
Reexamination Certificate
active
06323574
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a polyphase motor such as a three-phase motor having a stator having six magnetic poles and four magnetic poles each composed of permanent magnet, and a four-phase motor having a stator having eight magnetic poles and four magnetic poles each composed of permanent magnet.
In a conventional three-phase motor (not shown) which is operated at an arbitrary speed and output, a rotor containing permanent magnets in the circumferential direction is fixed and disposed inside a stator having six magnetic poles, and by changing the exciting magnetic polarity of each magnetic pole of phases A, B, C of the stator, the rotor is rotated.
The three-phase motor having such a structure is controlled by a driving unit. That is, a first transistor series circuit, a second transistor series circuit and a third transistor series circuit are connected between +E terminal and grounding. A core wire of each phase is connected to a first joint of the transistor, a second joint point of the transistor, and a third joint of the transistor.
On the other hand, a micro computer is provided so as to input a speed instruction pulse for controlling the rotation speed to an AND gate and a rotation position of the three-phase motor is detected by a position detecting signal generating circuit provided with hall devices each time when the rotor is rotated by 30°. The position detection signal is inputted to the AND gate circuit via a delay circuit. The delay circuit adjusts a timing for supplying the position detection signal to the AND gate circuit by controlling the delay of the position detection signal. An interval of the delay is controlled by the micro computer depending on load and acceleration of the motor.
The AND gate circuit obtains the logical product of a speed instruction pulse from the micro computer and a position detection signal from the delay circuit and its logical product output is outputted to a six-step ring counter. This ring counter changes an output to six output lines in succession depending on input of the logical product output from the AND gate circuit and repeats this procedure to supply the output to an invertor IC. The invertor IC fetches an output from the ring counter and controls switching of the respective transistors so that the three-phase motor is operated in step order for phase excitation or in inverse step order.
In this conventional three-phase motor, a voltage between respective lead wires Y or &Dgr; connected of three-phase windings for phases A, B, C is changed over between normal direction and inverse direction by switching operation of six transistors so as to drive the rotor
3
. Therefore, switching frequency per a rotation is as large as six, and the fact that the switching frequency is large is an obstacle for high-speed driving of the motor. That is, to prevent a shortcircuit of a transistor bridge composed of transistors, a high side transistor needs to be actuated after a low side transistor is completely interrupted, and a waiting time is thus required. Therefore, an expensive power transistor having a high switching speed needs to be chosen as a transistor so as to achieve high-speed driving.
As described above, conventionally, to achieve high-speed driving, a number of expensive power transistors having a high switching speed have to be used, and therefore, there are disadvantages in that a space of a circuit portion and the production cost increase.
BRIEF SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a polyphase motor capable of reducing the number of switching devices used for controlling power supply to each winding thereby making it possible to reduce a space for a circuit portion of a driving unit and the production cost thereof.
To achieve the above object, according to an aspect of the present invention, there is provided a polyphase motor apparatus comprising: a rotor having a rotating shaft and a plurality of permanent magnets connected therearound; a stator for holding the rotor rotatably and provided so as to surround the rotor, having n phases (n is an integer which is three or more) and n×m (m is an integer which is one or more) magnetic poles, in which each of n pairs of the magnetic poles adjacent to each other is wound with a core wire an end of which is connected to a common terminal (+E), such that one magnetic pole is a first magnetic polarity and the other magnetic pole is a second magnetic polarity different from the first magnetic polarity, and an n-phase voltage from outside is applied between the common terminal and the other end of the core wire of each pair so as to generate a magnetic field for rotating the rotor.
With such a structure, when a current flows through a core wire of a magnetic pole of a single phase, a magnetic field by S pole and N pole is generated, so that a “state in which different magnetic fields are generated in parallel” necessary for rotating the rotor with a single current is produced. Thus, as current for rotating the rotor, currents in the normal direction and inverse direction are not required for each phase, but by providing a single direction current for each phase appropriately, a necessary magnetic field is obtained. Therefore, although in a conventional apparatus, a driving unit for three phases for example requires current control with six transistors, according to the present invention, a necessary rotation is obtained by supplying a current under current control with three transistors because the present invention provides a single direction current. Therefore, the space of the driving unit can be largely reduced and the control method can be simplified.
According to a preferred embodiment of the present invention, the stator is a stator for holding the rotor rotatably and provided so as to surround therearound, having n phases (n is an integer which is three or more) and n×m (m is an integer which is one or more) magnetic poles and each of n pairs of the magnetic poles adjacent to each other is wound with a core wire an end of which is connected to the common terminal (+E) such that one magnetic pole is a first magnetic polarity and the other is a second magnetic polarity different from the first magnetic polarity, the core wire wound around both the magnetic poles being in parallel, and an n-phase voltage from outside is applied between the common terminal and the other end of the core wire of each pair so as to generate a magnetic field for rotating the rotor.
Thus, a correspondence to driving with a low voltage power supply is facilitated. Although at an adjacent magnetic pole, rise of excitation is delayed due to an influence of residual magnetic flux of a phase previously excited, at the other magnetic pole, excitation is started at the same time when an electric power is supplied, so that the delay of excitation of both adjacent magnetic poles is eliminated more than a case of series connection. Thus, a response to an instruction speed can be improved.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
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Dinh Le Dang
Frishauf, Holtz Goodman, Langer & Chick, P.C.
Ramirez Nestor
Toshiba Tec Kabushiki Kaisha
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