Abstract: The cleaning device comprises a dummy disc having at least a hole covering an area in which a control signal is to be recorded, a flexible disc member coaxially arranged on the dummy disc and secured thereto at an inner periphery thereof and a cleaning member attached on one surface of the flexible disc facing to the dummy disc and protruding downwardly through the hole of the dummy disc. The cleaning device is set on a turn table integrally attached to a rotary shaft of the disc player and made in light-pressure contact with an optical pick-up raised so that a lens surface of the pick-up is wiped away thereby during its horizontal movement. In a case where the lens collides with the cleaning member, the cleaning member is pushed up by the lens through the hole of the dummy disc due to the flexibility of the flexible disc, so that a mechanical damage of the lens surface is prevented.

Abstract: A driving current control circuit capable of controlling the logarithmic base current of two transistors in a current driver to control a drive current for a motor. This control circuit controls the current of the current regulator depending on a control signal, thereby controlling the driving current for the transistors in the current driver. The control circuit includes an output current mirror composed of two output-side transistors and a single input-side transistor. The two output-side transistors control the inflow and outflow of the driving current for the current driver. A single phase compensating condenser is connected to the input-side transistor. This arrangement makes the entire circuit simple and compact and causes an improved controlling characteristic.

Abstract: A controlling apparatus for an induction motor for controlling the induction motor in high efficiency having a converter for supplying an electric power to the induction motor, a rotational speed detector of the induction motor, a controlling means of the converter for holding a torque of the induction motor constant while the rotational speed of the induction motor is lower than a base rotational speed and to decrease a secondary magnetic flux of the induction motor according to the rotational speed while the rotational speed of the induction motor is over the base rotational speed, and a means for varying the secondary magnetic flux according to a terminal voltage of the induction motor so as to hold the terminal voltage a predetermined constant voltage while the rotational speed of the induction motor is higher than the predetermined speed.

Abstract: In a plural phase electric motor, a control method senses regeneration current from a non-energized phase and commutates to the next state. In the next state, the unenergized phase of the present state is energized in a polarity opposing the regeneration current of the present state, such that during the next state, energization current is directed in the last noted phase in a direction opposite to the regeneration current of the present state. In the state prior to the present state, the unenergized phase of the present state is energized in a polarity aiding the regeneration current of the present state, such that during the prior state, energization current is directed in the last noted phase in the same direction as the regeneration current of the present state. In the preferred embodiment, all of the commutation switches are periodically simultaneously turned off for a given blanking interval, and the regeneration current is sensed on a common DC bus during such interval.

Abstract: A polyphase induction motor is driven from an inverter having a set of switches activated in prescribed on-off patterns to provide forward and reverse voltage vectors and a zero vector for controllably energizing the motor. Memories are provided on which there are written forward voltage vector data for forwardly energizing the motor, reverse voltage vector data for reversely energizing the motor, and zero vector data for de-energizing the motor. The voltage vector data and zero vector data are selectively read out from the memories in order to cause the inverter to generate in real time the corresponding voltage vectors and zero vectors needed for the motor to be quickly revolved to, and set out of rotation exactly in, a desired angular position. For such optimum motor speed control an ideal control curve is predefined which represents the ideal relationship between the motor speed and the difference between the actual and the desired angular position of the motor.