Mitsubishi Denki Kabushiki Kaisha

Ryohei Uchida

Masahiko Akamatsu

Tatsuo Yamasaki

Mitsuru Kitano

Munehiko Mimura

Toshifumi Fujii

Ippei Hagiwara

Toshio Tatsutani

Yoshinobu Morimoto

Toshio Idei

Satoshi Utsumi

Sadanobu Kawabe

Kosuke Hasimoto

Yoshinoku Morimote

A magnetic video reproducing apparatus employing a well-known rotational two-head system, a helical scan system and an azimuth system comprises a position detecting means for detecting the positions of the two heads and a dropout detecting means for detecting a dropout of the reproduced signal output from the two heads. A time difference detecting circuit is provided for detecting a time difference between the output from the position detecting means and the output from the dropout detecting means. A time period converting circuit is also provided for converting the time difference detected output to an output signal of a time period associated with the time difference output. A driving circuit is provided for driving a capstan shaft driving motor. The time period converting circuit is adapted such that the time period of the output therefrom may cause the capstan shaft driving motor to be driven so that the dropout timing and hence a noise zone on the screen may coincide with the change over between the two heads, whereby a noise zone due to a dropout of the reproduced signal comes to the upper or lower end of the screen.

Magnetic video reproducing apparatus having still picture reproducing

A control apparatus of a transistor motor comprises an addition reference setting circuit (203), a positive voltage addition circuit (204 and 207), a negative voltage addition circuit (205), and a positive/negative voltage addition circuit (202). The addition reference setting circuit (203) is adapted to produce reference values VC and VD. The addition is made of the magnitude of the positive-going component with respect to the reference value VC out of the peak values of the feedback voltages (VU, VV and VW) in the positive voltage addition circuit, whereby the output VAA is provided. Addition is also made of the magnitude of the negative going component with respect to the reference value VD out of the peak values of the feedback voltages in the negative voltage addition circuit, whereby the output VB is provided. The above described outputs VAA and VB are added to each other in the positive/negative voltage addition circuit, whereby the output VE is provided. The output voltages of the hall-effect devices (.alpha., .beta. and .gamma.) are controlled such that the magnitude of the output VE may be consistent with the magnitude of the control signal (VF) in a difference control circuit (209 and 201). Accordingly, it was confirmed that a torque ripple of the motor is drastically mitigated.

Control apparatus of transistor motor

A plurality of slots are disposed at equal angular intervals on one portion of a circular ring-shaped field magnet fixed to a motor's rotor to run radially of the magnet. Alternatively, short rods made of a soft magnetic material may extend radially outwards from the lateral surface of the magnet to form the slots between them. Three magnetic sensor elements are disposed at equal angular intervals of 120 degrees on a motor's stator to face successively the slots during the rotation of the rotor.

Rotation sensor device

A transformer device comprises a saturable magnetic core having control and controlled windings, the saturable magnetic core being controlled in a feedback mode through switch means such as transistor switch means. The transformer device may comprise two magnetic cores and changes in magnetic resistance between the two magnetic cores are differentially fed back and amplified to cause an oscillative switch means to be turned on and off. A current to be detected flows in the control winding and detected by the controlled winding. The detected output corresponds to the polarity and the absolute value of the current supplied to the control winding. The transformer device not only can detect or measure the primary current but can identify the polarity thereof, differing from prior art dc current or potential transformers. The transformer device of the invention operates substantially free of slot-ripple inherent in the prior art transformer. In the transformer device of the invention, the magnetic core is driven always in an unsaturated region whereby the ripple ascribed to the exciting current is minimized. Thus the transformer device is ideal for applications where an instantaneous output in value and polarity corresponding to the primary current is desired substantially free of ripple component. The effective use of the transformer device includes current or voltage measurement, electric motors and other industrial machines, as well as inverters and choppers.

Transformer device

A chopper control device is disclosed, comprising: a series circuit having a dc power source, a dc load, and a thyristor; a transistor connected in parallel to the thyristor; a current transformer having a primary winding for detecting the load current; and another transistor for deriving a current from a secondary winding of the current transformer and supplying it to the base of the transistor.

Chopper control device

Four thyristors are interconnected into an AC bridge circuit. With an AC source connected across inputs to the bridge circuit, a DC motor is connected across outputs of the bridge circuit while the thyristors are operated in the phase control mode to control the power supply to the motor from the AC source. In the absence of the AC source the DC motor is serially connected to a battery across the outputs of the bridge circuit with the thyristors operated in the chopping control mode. Also, in the presence of the AC source, a rectifier bridge including thyristors and diodes can be connected across the battery to exclusively charge it from the AC source.

Control apparatus

A series combination of thyristor and diode is connected across another series combination of thyristor and diode to form a bridge circuit. Serially connected reactor and capacitor are connected across one of the thyristor in the chopping control mode in the use of a DC source and disconnected from both thyristors in the phase control mode in the use of an AC source in order to drive a DC motor by either of the DC and AC sources. A battery can be connected across the bridge circuit through the DC motor. Either one of the series combinations may be formed of the diode and two thyristors one of which is always connected across the serially connected reactor and capacitor.

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Himeji, Japan

Ryohei Uchida