Westinghouse Electric Corporation

Frederick O Johnson

John Rosa

Warren C Fry

Joachim E Wolf

Andrew P Kruper

Charles W Maiden

A transportation apparatus having improved brake control. The actual speed of the transportation apparatus is compared with a reference speed signal, and when the actual speed exceeds the reference speed a brake is applied to slow the transportation apparatus. Rather than simply applying the full torque of the brake abruptly, the present invention discloses an apparatus for pulse duration modulating the control signal for controlling the brake. The brake responds to the average of the pulse duration modulated control signal such that braking torque is applied gradually and essentially linearly. The device can also be used in an acceleration situation to provide gradual acceleration of the transportation apparatus.

Conveyor brake control

To eliminate thyristor failure due to voltage imbalance across series-connected thyristors during reverse voltage recovery caused by current discontinuity under continuous pulse application to the thyristors, the continuous pulse is discontinued after a time interval of application which is a function of the control signal establishing the firing delay angle. The continuous pulse is reinstated as in a double-pulse mode, thereafter, with the same controlled duration.

Method and apparatus for firing angle control of series connected

An electronic motor control system is taught herein which utilizes a tachometer check circuit. The tachometer check circuit is an electrical circuit which is interconnected with the output terminals of the tachometer. The circuit is utilized when the tachometer is at standstill to determine if the tachometer is functional, that is, is it internally correctly wired to produce an expected signal upon rotation. If such is the case, then motor start-up may take place. A second test is performed after motor start-up for determining if an appropriate amount of output voltage is being produced by the tachometer during the start-up phase. This is based on expected values of voltage during a short period of time after start-up. If such is not the case, the motor control system is disabled and the motor is stopped. The system is utilized for embodiments which include AC tachometers as well as DC tachometers used on unidirectional or bidirectional rotational systems.

Tachometer check apparatus

A regulated DC power supply has a converter having a plurality of switches which, upon proper regulation of their conduction, rectify an AC current. The converter produces a current feedback signal. A reference generator produces a plurality of adjustable reference signals each representative of one value of a load current and produces a predetermined, standby, reference signal representative of a standby load current. One of the adjustable reference signals, the standby reference signal, and the current feedback signal are added to produce a control signal. The control signal is compared to a signal representative of the AC source voltage. Firing signals, used to regulate the conduction of the switches, are produced in response to the existence of a predetermined relationship therebetween. In the event that all of the adjustable reference signals have a value of zero for a predetermined period of time, the firing signals will be inhibited from regulating the conduction of the switches.

Regulated DC power supply

Converter apparatus including gate drive control of the stored energy type. Control logic arms the next controlled rectifier device to be gated a predetermined period of time following the gating of the immediately preceding controlled rectifier device in the gating sequence.

Converter apparatus

Converter apparatus including a power converter having controlled rectifier devices connected, and gated in a predetermined sequence, to interchange electrical power between a source of alternating potential and a direct current load circuit, a phase controller for controlling the conduction angle of the controlled rectifier devices, and circuitry for maintaining synchronous operation between the phase controller and the power converter. The circuitry for maintaining synchronous operation constrains the conduction angle between predetermined end stops by logically combining first and second logic signals developed for each controlled rectifier device from the source of alternating potential, with a logic signal associated with the immediately preceding controlled rectifier device in the gating sequence.

An elevator system having an elevator car operable in the up and down travel directions in a selected one of first and second speed modes. The elevator system develops a bi-directional speed pattern signal from a selected one of first and second unidirectional speed pattern input signals, with the polarity of the bi-directional speed pattern signal being responsive to the selected travel direction. su

Elevator system

A digital pulse generator for firing thyristors in a polyphase converter system is described in an hybrid analog-digital and in an all digital form. A phase locked oscillator associated with a digital counter generates timing waveforms synchronized with the phase lines to establish firing angles in relation to a reference signal. Each firing pulse triggers the logic circuit of a distributor and a multiplexer is coupled with such logic circuitry in order to insure that the proper timing waveform is selected so as to match the selection of the next thyristor to be fired.

Digital firing pulse generator for thyristor power converters

A method and apparatus are disclosed for reducing effective inductance and providing balanced line-to-line voltages in induction machine dynamic braking circuits which utilize braking resistors to substantially increase the full torque braking range of the machine. The current phase lag caused by the inductive property of conventional braking resistors, is substantially reduced by rectifying the current provided to the braking resistor through a three-phase rectifier bridge. This reduction of the current phase lag permits a reduction in the capacitance required to compensate for the effective inductance in the dynamic braking circuit. Furthermore, because the braking currents flow through a common braking resistor, the line-to-line stator motor voltages are inherently balanced. If the prior art braking impedance control is also employed, the rectifier bridge need carry current only if dynamic braking is required when motor voltage is greater than the maximum voltage of the inverter supplying the machine. Where the braking resistor may be varied in a step-wise manner, the amount of dynamic braking capacitance needed for inductive compensation is reduced below the substantial reduction realized for a non-variable resistor. Depending upon the required degree of performance and the allowable complexity of the braking circuit, the prior art braking impedance control may be eliminated and the effective impedance of the common braking resistor may be varied in either a continuous or a step-wise manner.

Growing community of inventors

Monroeville, PA, United States of America

Frederick O Johnson