The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Nov. 09, 1976
Filed:
Jun. 19, 1975
Warren C Fry, Bulleskin, PA (US);
Frederick O Johnson, Monroeville, PA (US);
John Rosa, Penn Hills Township, PA (US);
Westinghouse Electric Corporation, Pittsburgh, PA (US);
Abstract
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.