Abstract: A control system for stopping a spindle at a prescribed rotational position having a position control loop for driving a spindle so that a positional deviation between the present rotational position of a specified point on the spindle and a predetermined rotational position at which the specified point is to be stopped, is reduced to zero to stop the specified point on the spindle at the predetermined rotational position. Fine and coarse voltage signals are utilized for the final positioning process.

Abstract: A system for controlling the rotation of a spindle which includes motor, a speed detector for detecting the speed of the motor and for producing a signal indicative of the actual speed thereof, a speed control circuit for controlling the motor so as to narrow a deviation between the signal indicative of the actual motor speed and a command speed signal, a spindle which is driven by the motor, and an orientation control circuit for producing a position deviation signal on the basis of the rotational position of the spindle and a commanded stopping position, wherein the spindle is rotated at a commanded speed by the speed control circuit and rotationally controlled in response to an orientation command signal so as to reduce the position deviation signal to zero.

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: 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.

Abstract: A device for detecting opposite phases and an open phase in an input three-phase voltage for a DC motor, wherein the input three-phase voltage is rectified by a three-phase bridge circuit and supplied to the armature of the DC motor. The input three-phase voltage is supplied to the three-phase bridge circuit when the maximum level is equal to or less than the reference voltage, while the input three-phase voltage is not supplied to the bridge circuit when the maximum level is greater than the reference voltage. In this case, both opposite phases and an open phase can be detected by using a common device. In addition, only two phases, such as U- and W-phases, are used for detecting opposite phases and an open phase no matter how these phases may be generated in any phase such as U-, V- or W-phase of the input three-phase voltage. As a result, the device is small in size, simple in electrical construction and low in cost.

Abstract: A system for a DC motor associated with a field winding and driven by using a three-phase anti-parallel thyristor bridge circuit, comprising a first means for controlling an armature current I.sub.a flowing through an armature of the DC motor, and; a second means for controlling a field current I.sub.f flowing the field winding by obtaining the feedback values of a voltage E.sub.a of the armature and the field current I.sub.f and by changing the maximum level of the current I.sub.f in accordance with a three-phase alternating voltage V.sub.ac applied to the three-phase anti-parallel thyristor bridge circuit. In the system, when the three-phase alternating voltage V.sub.ac decreases to a value lower than a predetermined value V.sub.o, the field current I.sub.f are decreased so that the armature voltage E.sub.a is decreased.

Abstract: An actual speed N of a DC motor and an armature current Ia are detected to detect the motor output N.times.Ia. The motor speed is changed so that the detected motor output may not exceed a predetermined value. The spark generation of the motor brush is prevented when an over load is applied to the motor.

Abstract: A system for controlling DC motors of the type employing permanent magnets as field poles. The firing phase angle of a thyristor is controlled in response to an error signal representative of an error between a commanded motor speed and an actual motor speed. For preventing demagnetization of the permanent magnets due to the armature reaction, the clamp level of the error signal is changed in accordance with the actual motor speed.

Abstract: A speed detector produces a spindle speed signal proportional to the revolving speed of a spindle. A specified position detector provides a specified position signal when the spindle assumes a specified rotational position. A spindle motor speed control unit controls the spindle motor so that the motor speed agrees with a speed command. When spindle orientation is requested, one integrator circuit responds to the specified position signal to integrate the spindle speed signal. The output from the integrator circuit is applied to the speed control unit in place of the speed command.