Abstract: An automatic tool changing mechanism includes a spindle mechanism (11) having at least a spindle (11a) and a first gear (11b) rotatable in unison with the spindle; a spindle motor (12) for rotating the spindle; a tool magazine (20) having at least a storage unit (20b) for storing a plurality of tools (21), a second gear (20c) rotatable in unison with the storage unit, and a slider (20e) slidably mounted on the spindle mechanism; a Z-axis motor (19a) for moving the spindle mechanism in the direction of a Z-axis; a constraining member (23) for constraining the tool magazine against movement thereof in the direction of the Z-axis and a control circuit (102, 103) for controlling the indexing. During machining operation, the first and second gears are brought out of mesh with each other, and the spindle is rotated by the spindle motor at a prescribed speed to enable a tool mounted on the spindle to machine a workpiece.

Abstract: A rotor structure comprising a shaft and a magnetic pole assembly comprising radially disposed permanent magnets and yokes. The magnetic pole assembly is supported by the shaft through end plates. The end plate has a recess to receive the end of the magnetic pole assembly. The magnetic pole assembly can be fit into the end plates.

Abstract: Through holes (11, 12, 13 . . . ) are made at predetermined locations of a stator core (1). Reinforcing bars are inserted thereinto while fixed to the stator core by welding (81, 82, 83 . . . ). The stator core is supported between a front bracket (31) and a rear bracket (32) from both sides. Front side tap bolts (91, 92, 93 . . . ) and rear side tap bolts (61, 62, 63 . . . ) are engaged through the front bracket and the rear bracket with internal threads of both ends of the reinforcing bars, thereby fixing in place the stator core, front bracket, and rear bracket. By the foregoing structure, it is possible to improve the heat radiation action of a stator core, and also achieve a compacter motor.

Abstract: A system for detecting the rotational speed of a rotating body comprising the steps of generating two kinds of signals A and B having alternating wave forms and corresponding to the rotational speed of the rotating body by means of position-detecting devices (5a, 5b), the signals A and B having the same amplitude and having phases deviating by 90.degree.

Abstract: A stator of an electric motor comprises a laminated iron-core (1) having dovetail grooves, end plates (2) and steel bars (3) which are accommodated in the dovetail grooves and have a trapezoidal shape in cross-section. The steel bars (3) are arc-welded to the laminated iron-core (1) and to the end plates (2).

Abstract: An inverter circuit having a bridge circuit comprising a plurality of switching elements connected in the form of a bridge for converting, into alternating current, a DC voltage produced by a DC voltage generating unit and which is received through a first switching circuit. The inverter circuit includes a pair of diodes and a spike absorbing capacitor which constitute a series network wherein the diodes are connected so as to be forward biased with respect to the DC voltage and the spike absorbing capacitor is connected between the diodes. The series network is connected in parallel with the bridge circuit and is connected to the DC voltage generating unit through the first switching circuit. The spike absorbing capacitor is connected in parallel with a smoothing capacitor of the DC voltage generating unit.

Abstract: A system for operating an induction motor at variable speeds, which is particularly effective when an induction motor is to rotate at a very low speed of several r.p.m. or less. The system produces polyphase sinusoidal signals of a frequency which corresponds to the difference between a command speed and the actual speed of the induction motor, the number of phases of the sinusoidal signals being equal to the number of phases at which the induction motor operates, a sinusoidal carrier wave having a constant frequency of from 50 to 400 Hz and a constant amplitude, and polyphase induction motor drive signals formed by modulating the carrier wave by the polyphase sinusoidal signals. The induction motor drive signals are amplified up to a prescribed value and then applied to the induction motor to energize the stator for each respective input phase so that the rotor of the induction motor will be caused to rotate at a very low speed.

Abstract: An AC motor control method and apparatus therefor, for controlling an AC motor 11 by holding the excitation current I.sub.0 of the AC motor 11 constant and varying primary current I.sub.1 in accordance with a speed deviation .DELTA.n. Stored previously in a memory device 18 are a torque T-slip frequency .omega..sub.s characteristic, a slip frequency .omega..sub.s -primary current vector I.sub.1 characteristic, and a slip frequency .omega..sub.s and phase .phi..sub.1 characteristic which take secondary leakage reactance into account. Slip frequency .omega..sub.s, primary current vector I.sub.1 and phase .phi..sub.1 are read out of the memory device in accordance with the torque command T obtained from the speed deviation .DELTA.n, whereby three-phase current commands i.sub.u, i.sub.v, i.sub.w are produced. Accordingly, torque irregularity is suppressed and an excellent response obtained.

Abstract: A control circuit for driving an induction motor wherein an AC voltage is converted into a direct current by a rectifying circuit and the direct current is converted into a signal having a variable voltage and frequency by a transistor inverter connected in parallel with a smoothing capacitor, and a regenerative circuit is connected in parallel with the inverter, and a first monitoring circuit is provided for comparing the terminal voltage V.sub.C of the smoothing capacitor and a first reference voltage E.sub.1 when braking is to take place. When the condition V.sub.C .gtoreq.E.sub.1 exists, the transistor inverter is disabled but the regenerative circuit is allowed to operate. When the condition V.sub.C <E.sub.1 exists, the transistor inverter is operated in the regenerative braking region. A second monitoring circuit is provided for comparing the smoothing capacitor terminal voltage V.sub.C and a second reference voltage E.sub.2 (E.sub.2 >E.sub.1). When the condition V.sub.C .gtoreq.E.sub.

Abstract: A rotary electric motor of a sealed type comprising a heat pipe in a rotor shaft and a plurality of air vents in a stator. In the operation of this motor, a rotor mounted on the rotor shaft is cooled by the heat pipe and simultaneously, the stator is cooled directly by the air flowing therethrough.

Abstract: A speed detector including a circular rotational member having a plurality of equally spaced-apart teeth on the outer circumference thereof, and first and second magnetic sensors. The first and second magnetic sensors each comprise a permanent magnet, a magnetic pole which permits the passage therethrough of a magnetic flux generated by the permanent magnet, and a detection coil wound on a portion of the magnetic pole. The magnetic poles of the first and second magnetic sensors are disposed in close proximity to, and arranged to face, the teeth on the rotational member, whereby each magnetic sensor produces an alternating output signal as the rotational member rotates, the frequency of each output signal being proportional to the speed of the rotational member.

Abstract: An induction motor drive apparatus of the type having a speed detector for detecting the rotational speed of an induction motor, speed command device for producing a command speed, and an error amplifier for amplifying a difference between the rotational speed of the induction motor and the command speed, the induction motor being driven by so controlling the amplitude of the primary current as to vary the amplitude of the secondary current in accordance with the difference between the rotational and command speeds. Included are two-phase sinusoidal wave generating device for generating two sinusoidal signals displaced in phase from one another by .pi.

Abstract: An apparatus for controlling the operation of an AC motor wherein braking energy at the time of a reduction in motor speed is disposed of by regenerative braking. The apparatus includes a rectifier connected to the AC power source, a smoothing capacitor, a variable-voltage variable-frequency inverter, and a regenerative thyristor bridge circuit connected between the inverter and the rectifier through switching transistors. There is also provided a firing control circuit for controlling the firing of each thyristor in the thyristor bridge circuit and for controlling driving of the switching transistors in synchronism with the firing of the thyristors, the braking energy being fed back to the AC power source when the AC motor undergoes a reduction in speed. The apparatus is small and can be constructed simply and inexpensively.

Abstract: A system for driving an alternate current motor including a pulse width modulation inverter having the two-range driving characteristics, wherein the motor is driven by the pulse width modulation output having a simulated sine wave form at the speed lower than the base speed of the motor and by the pulse width modulation output having a rectangular wave form at the speed higher than the base speed of the motor.

Abstract: A method of, and apparatus for, controlling the feed rate of a cutter in a machine tool of the type in which a spindle is rotated by an electric motor having operating regions of constant torque and output characteristics so as to render constant the circumferential speed of a workpiece while the workpiece is subjected concurrently to a machining operation by moving a cutter into contact therewith. The apparatus includes mechanism for computing the maximum cutter feed rate, the circumferential speed V.sub.c of the workpiece, the cutting width d of the cutter and the maximum cutting quantity Q.sub.max which is decided by the maximum power P.sub.max of the motor, mechanism for computing a spindle speed N.sub.s from the circumferential speed V.sub.c and the outer diameter D of the workpiece, mechanism for comparing the magnitudes of a base speed N.sub.b and the spindle speed N.sub.s, where the base speed N.sub.

Abstract: Disclosed is an induction motor drive apparatus which brings the actual speed of an induction motor into coincidence with a command speed by varying the frequency and effective value of a three-phase AC voltage applied to the induction motor. The apparatus includes an inverter for generating three-phase AC voltage, a speed deviation signal generator, an amplitude controller for controlling the amplitude of the speed deviation signal, an adder for adding together a voltage signal which conforms to the actual speed and the speed deviation signal which has been controlled, a rectangular waveform signal generator, and a pulse width modulator. The rectangular waveform signal generator is adapted to produce a three-phase rectangular signal whose frequency is proportional to the output voltage value of the adder.

Abstract: An induction motor drive apparatus brings the actual speed of an induction motor into coincidence with a command speed by varying the frequency and effective value of a three-phase AC voltage applied to the induction motor and limits the torque of the induction motor in the low speed region by controlling an amplitude of a speed deviation signal below a prescribed value.

Abstract: An apparatus for controlling the operation of an AC motor wherein braking energy at the time of a reduction in motor speed is disposed of by regenerative braking. The apparatus includes a rectifier which is connected to the AC power source, a DC link which includes smoothing capacitors and a regenerative transistor bridge circuit, a variable voltage-variable frequency inverter. Further provided are a diode which is connected between the rectifier and the transistor bridge circuit and which is biased in the reverse direction at the time of regenerative braking, and a firing control circuit for detecting the reverse bias voltage of the diode to control the firing of each transistor in the transistor bridge circuit, the braking energy being fed back to the AC power source when the AC motor undergoes a reduction in speed. The apparatus, which provides stable regenerative operation, can be constructed simply and inexpensively, and reduced in size.

Abstract: The invention relates to a speed control system which includes an inverter circuit for converting a direct current into a polyphase alternating current in the form of a rectangular wave by the switching action of transistors, and an inverter drive circuit adapted to apply control signals to the inverter circuit to bring its output frequency to a desired value, an induction motor being rotated by the alternating current supplied by the inverter circuit. The system features current detection means for detecting current that flows through the output side of the inverter circuit, and decision means for examining the output of the current detection means for a fixed period at a frequency higher than that at which the induction motor is driven.

Abstract: A DC motor control system which has means for detecting the rise and fall of a drive command signal to generate an ON ACCELERATION/DECELERATION signal and means for generating a current limit signal for driving a DC motor by the ON ACCELERATION/DECELERATION signal to produce a rated output and for driving the DC motor to produce an output 1/n times the rated output when the DC motor is switched from an acceleration state to a stationary state. When the DC motor is accelerated or decelerated by the drive command signal, a current for obtaining the rated output is applied to the armature of the DC motor and, in the stationary state, even when a load on the DC motor is maximum a current for obtaining an output 1/n times the rated output is applied to the armature of the DC motor to reduce the output of the large-output DC motor, thereby providing an enlarged constant output DC motor range.