Abstract: A braking and speed-control circuit is disclosed which prevents excessive current from being dissipated in a DC series motor. The circuit includes two free-wheeling diodes, a forward-biased diode, and a thyristor. The forward-biased diode is placed between the field coil and the armature winding of the motor. One free-wheeling diode is placed across the entire motor circuit, including the forward-biased diode. The other free-wheeling diode is placed across the forward-biased diode and the field coil. The thyristor can short across the forward-biased diode and the armature winding.

Abstract: An instantly variable constant current control is interposed between a bank of batteries and a motor. The variable constant current control comprises a series pass transistor operating in a linear mode and controlled by a reference voltage from a potentiometer coupled to an accelerator pedal. Correction voltage from the series pass transistor circuit is proportional to current. The accelerator reference voltage and the current correction voltage are compared in a linear operational amplifier which controls the "on" resistance of the series pass transistor.

Abstract: In a helical scan video tape recorder, a capstan motor is speed-controlled in response to a command frequency of a command signal under a special reproducing mode called a SEARCH MODE. A speed servo loop for the capstan motor for this purpose includes a pair of pulse converters and a pair of integrating circuits for comparing the command signal and a rotation signal generated by a frequency generator attached to the capstan motor. A time constant of the integrating circuit for the command signal path is selected to be smaller than that of the integrating circuit for the rotation signal, so that the capstan motor is driven in a pulse drive mode below a predetermined speed.

Abstract: A direct current motor controlling apparatus determines the operational speed of one or more direct current motors such as traction motors propelling a passenger vehicle along a track. The speed of the motor is established by changing the on and off conduction ratio or duty-cycle relationship of a switch device to determine the field current and the armature voltage of that motor. The present apparatus utilizes solid-state switch devices to determine the mode of operation of the motor control apparatus which solid-state switch devices are more reliable and more simple in operation and less expensive to maintain.

Abstract: A continuous speed control and braking circuit for a DC propulsion motor having armature and field currents set largely independent of each other to permit operation in the field weakening region of the motor. A direct current control element is pulsed for setting the armature current; a series circuit containing the field winding and a switch is connected in parallel to the DC control element; and a field current bypass diode is shunted across the field winding.

Abstract: An SCR motor speed control system is provided with circuitry for fast braking of the motor. The circuitry senses when it is desired to stop the motor and simultaneously short circuits the motor armature and applies half-wave rectified line voltage to the motor field windings.

Abstract: An electric vehicle traction motor control circuit includes separate armature and field current controls. The armature control includes a difference amplifier connected to compare a current demand signal with an actual current signal from a transducer and a switching circuit controlled by this difference amplifier. The field control includes a second difference amplifier which operates to weaken the field current in either of two eventualities. In motoring the second difference amplifier receives its input via a start up circuit which connects the output of the first difference amplifier to the input of the second difference amplifier when the switching means has been in a first state for more than a predetermined time. In this case the field is weakened in accordance with the short fall of the output of the first difference amplifier below a first reference level.

Abstract: A circuit for the energy-conserving braking of an electrically powered vehicle having a series-wound direct-current motor with field winding and armature connected in series with a high-ohmic resistance across the battery connection is effected by a main thyristor is provided with a second thyristor serving to quench the first thyristor. A capacitor (quenching capacitor) is included in a commutating device or network parallel to the main thyristor. A voltage sensor responsive to the voltage level at the junction between the condenser and the main thyristor controls the commutating circuit.

Abstract: A circuit for driving and braking a variable speed D.C. motor. A braking resistance has a terminal connected to the field winding of the motor. A diode is connected between this terminal and a quenching diode of the braking circuit to reduce the limiting effects of voltages produced across a reversing condenser in the braking circuit.

Abstract: A circuit arrangement for record players is disclosed for presetting of the disc. The disc is set back by a specific rotation angle before starting the turntable so that it will accelerate to the proper angular velocity at the proper time for synchronizing program material.

Abstract: An automatically-openable-and-closable-door operating apparatus uses a capacitor torque motor in order to automatically open or close the door. When opening or closing the door, an exciting coil of the motor is first short-circuited as the door approaches the open or close terminal so that the motor undergoes a dynamic braking to absorb an inertia of the door and to decelerate the door. Thereafter the short-circuiting or connection and the disconnection across the exciting coil are repeated alternately to have the motor produce a driving force and a braking force alternately so that the door may be brought into its opening or closing terminal position at a low speed without accompanied by shocks.

Abstract: A pulse width modulated DC motor speed control circuit for models including a demodulator for receiving an input pulse having a width which may vary from a reference width, and for generating a first positive output pulse having a width proportional to the variation when the width of the input pulse is less than the reference width and for generating a second positive output pulsehaving a width proportional to the variation when the width of the input pulse exceeds the reference width, and a braking circuit for receiving the first output pulse and in response thereto causing any back EMF generated by the motor to be shorted for the duration of the output pulse, and a driving circuit for receiving the second output pulse and in response thereto connecting a source of power across the motor for the duration of the output pulse.

Abstract: A speed control device for use in a battery-powered vehicle wherein a shunt field current in a compound electric motor for driving the vehicle having a reactor connected in series therewith can be selectively controlled by using a variable resistor included in the circuitry and operatively interconnected to an accelerator pedal so that the resistance to the shunt field current may be changed accordingly to the extent of stepping-down on the pedal by the operator. The speed control device also features that a part of the vehicle's body structure of a ferro-magnetic material is used in combination as a core of the reactor so as to form a complete magnetic circuit for the reactor.

Abstract: A sewing machine driven by a motor which is adapted to be energized by an alternate current power supply and is phase controlled by means of thyristors. In a normal operating mode the conduction phase of the thyristors is made variable as a function of the extent of the depression of a foot controlled pedal, whereas in a low constant speed mode the thyristors are made conductive at a predetermined phase. The motor is coupled to a main shaft which is provided with a magnet located at a predetermined position, while a bracket arm is provided with a reed switch located at a predetermined position, such that if and when the foot controlled pedal is released, the reed switch is actuated to trigger the thyristors for reverse braking of the motor as a function of the counter electromotive force of the motor. Preferably, a timer is provided for interrupting the power supply after the lapse of a predetermined time period after the foot controlled pedal is released.

Abstract: A DC motor phase control system is provided in a system having a first controlled rectifier connected to an AC power supply and providing a positive rectified output and a second controlled rectifier providing a negative rectified output. A DC motor is controlled for forward and reverse rotation and is controlled in speed by the firing control of the rectifiers. The pulse indicating the zero point of the AC power supply voltage is delayed according to the actual speed of the motor and the delayed pulse is used as a reference pulse of the controlled firing pulses applied to the controlled rectifiers.

Abstract: In an apparatus having at least one rotary head for reproducing video signals recorded in successive parallel tracks extending obliquely across a tape which is advanced longitudinally and also has control signals recorded therein in predetermined positional relationship to the respective record tracks to be reproduced by a fixed transducer or head with a repetition rate that is dependent on the speed of advancement of the tape: a speed and phase control system for the rotary head or heads has a rotational speed detector for producing pulse signals representative of the rotational position of each rotary head and having a repetition rate that is a function of the rotational speed of the rotary head; a phase comparator for producing a phase responsive signal having a voltage level that is varied in response to changes in the relative timing of the reproduced control signals and the pulse signals; a digital device for producing a speed responsive signal having a voltage level that generally corresponds to the re

Abstract: A thyristor type control circuit for an electric traction motor for a road vehicle includes a thyristor chopper circuit controlling the average current through the armature and series field winding of the motor. The control circuit includes various switch arrangements for switching the armature connections for forward motoring, reverse motoring and electrical braking, but there is a current threshold detector circuit which prevents operation of these switch arrangements when the armature current exceeds a predetermined value. When braking is initiated, therefore, the current flowing is low and since the field winding is in series braking effort cannot build up. The invention provides a contact which connects the field winding to a d.c. supply while the armature current is below the threshold level during braking.

Abstract: A circuit for controlling the operation of a bi-directional motor. A motor energized to run in one direction is stopped by applying a reverse or braking current to its energizing field. When the motor is virtually stopped, means are provided to de-energize the motor to prevent the motor from reversing direction.

Abstract: A system for controlling the speed, torque and power of three phase a.c. motor. A binary logic circuit generates a variable frequency three phase signal which controls three driver pairs in an inverter to selectively apply either the positive voltage or the negative voltage of a direct current power source to each of the three motor phases. The three phase binary driver control signal is pulse frequency modulated below 60 cycles per second to operate the motor in a constant torque mode without varying the rectifier output voltage. The logic control signal also includes a delay to protect the drivers by assuring that one driver of a pair is "off" prior to turning the other driver "on". In addition the system comprises high response voltage and current limiting circuits to protect the system and to reduce the overcapacity requirement of the components. An accelerator/decelerator circuit achieves a nearly linear characteristic through the use of switching transistors to permit substantial cost savings.

Abstract: A separately excited speed-controlled D.C. motor which has constant armature current and pulse-controlled field current has its armature connected by way of a bridge rectifier and an inductor to an A.C. source of substantially greater r.m.s. voltage than the rated supply voltage of the armature, the inductor serving to regulate the armature current. The field winding is connected to a field excitation supply and to a thyristor chopper and the mean current through the field winding controlled by the thyristor chopper thereby to control the armature torque and therefore the speed. The field winding may comprise two field coils arranged to produce opposing magnetic fields, the thyristor chopper serving to control the net magnitude and direction of the motor field. A thyristor chopper may be provided in the armature circuit to maintain a constant armature current during plugging of the motor.

Abstract: A positioning drive with an electronic regulator for controlling the r.p.m. of a working shaft has a regeneratively coupled amplifier with variable negative feedback adjustable from a normally high value to a minimum value for the final braking action, whereby the shaft is abruptly brought to rest at a predetermined angular position.

Abstract: A direct motor drive system for a sewing machine wherein a low-inertia direct current motor coupled directly to the drive shaft is excited by a low impedence source of variable direct current voltage derived from a rectified alternating current signal at a manually controllable autotransformer. A needle-positioning circuit senses the needle position and either pulses or brakes the motor electrically so that the needle moves to a selected up or down position.

Abstract: A control circuit for an electrically driven vehicle has contactors for determining the direction of operation of the motor, but these contactors cannot be operated until the current flowing through the motor is below a predetermined level.

Abstract: In an electrically driven vehicle which is controlled by a thyristor chopper circuit having a main thyristor in series with the traction motor and a commutating thyristor for turning the main thyristor off, demand means is provided for setting a required current through the motor and firing the commutating thyristor when the required current is attained. An overriding control permits firing of the commutating thyristor when the main thyristor has been on for a predetermined period, and timing means operates when the overriding control is operative for setting the minimum off period of the main thyristor.

Abstract: A first train of pulses is generated at a first variable rate indicating the vehicle speed and a second train of pulses is generated at a second variable rate lower than the first rate indicating the wheel speed. A counter is provided having an input terminal receptive of the first train of pulses to count the same, a clear terminal receptive of the second train of pulses to clear the count and an output terminal at which a brake release signal is produced when the count reaches a predetermined number before it is cleared by one of the second train of pulses.

Abstract: In a control circuit for an electrically driven vehicle, there is an accelerator pedal which when depressed sets the armature current of a traction motor, and a brake pedal which when depressed provides electrical braking of the vehicle. The electrical braking is inhibited unless the vehicle speed is above a predetermined value.

Abstract: In a control circuit for an electrically driven vehicle, a traction motor drives the vehicle and there are contactors so that the motor can provide forward drive or electrical braking. The current in the motor armature is controlled by a pedal which also controls the contactor means. The action of the pedal can be modified in accordance with the position of the brake pedal of the vehicle.

Abstract: A speed control apparatus for use with a brushless direct current motor having Hall elements, which permits the associated motor to quickly regain the reference speed, or permits more uniform speed control of the motor than was conventionally possible.

Abstract: In a control circuit for an electrically driven vehicle, there is a thyristor chopper circuit which sets the current flow in a traction motor to a demanded level. The motor is capable of driving the vehicle forwardly or in reverse, and is also capable of effecting electrical braking. Whenever the motor is switched from its forward drive to its forward braking condition, or vice versa, the demand signal is set at a low level for a predetermined period.