Liebert Corporation

Robert W Baker

Jeffrey M Powell

James K Martin

Gary A Reichle

Stephen A Mowrer

Leonard E Orsak

A switch assembly and method includes a heat sink with two switch modules coupled thereto. Both of the switch modules are used in switching operations to make use of the entire heat sink, providing improved heat dissipation. The switch modules each have first and second switch devices, with each switch device having a gate terminal. A source voltage is applied to the switching modules and a positive portion of the source voltage is conducted through one switch device of the first switching module. A negative portion of the source voltage is conducted through one of the switching devices of the second switching module.

Switching assembly

A method and apparatus are disclosed for improving the disturbance pass through characteristics of a line interactive uninterruptible power supply (&ldquo;UPS&rdquo;). One disclosed technique uses a naturally commutated fast utility disconnect switch, wherein the switch is self commutated by the UPS inverter forcing the current through the switch to zero. A second disclosed technique uses a gate commutated fast utility disconnect switch and the associated snubber circuits, wherein the fast utility disconnect is opened quickly upon occurrence of a line fault and the energy generated in interrupting the line current is dissipated by the snubber circuits.

Apparatus and method for rapid fault detection and transfer in a utility-interactive uninterruptible power supply

The present invention provides an electrical circuit that measures the ground current due to insulation leakage in electrical heating elements. The circuit uses a CT to measure the current being supplied to at least one of a plurality of electrical heating elements. Using a comparator circuit and noise rejection circuitry to prevent erroneous tripping, once the current reaches a predetermined threshold, a signal is sent to a switch that causes a non-volatile memory device to clear thereby de-energizing the coil of the contactor that provides power to at least one of the heating elements.

Protective circuit for electrical heating element

An uninterruptible power supply capability is provided for line regulators of a variety synthesizing a desired waveshape for presentation to a critical load. A static switch is active intermediate the input of the line regulator and the line power supply to provide a power path during normal operation. Upon the occurrence of a line defect, a stand-by power path is provided which includes a source of d.c. stand-by energy such as rechargeable batteries which supply input to an unregulated inverter which, in turn, provides an unregulated input through an inductance to the input of the line regulator. Transfer is achieved by preliminary voltage level adjustment at the inverter and the inverter itself is employed to assure commutation off of the switching components of the static switch. Detection of line fault is made by detecting any instantaneous phase shift in the line input.

Uninterruptible power supply apparatus and power path transfer method

A controller for providing PWM drive to an inductive load incorporating an input rectifier bridge (24) the output of which is filtered by capacitors (106, 108) and which includes input impedance (116, 118) for limiting start-up current surges. A by-pass network (124) controlled from a high voltage sensor circuit (32) controls the by-pass network. The sensor circuit also provides an enablement signal (40) to a pulse width modulation circuit (42). A low voltage power supply (36) is coupled with the output (26) of the rectifier and filter function (24) to supply isolated power to the discrete driver networks of a driver circuit (48). The driver networks are controlled from the pulse width modulation circuit which, in turn, is controlled from a microprocessor (68). The drivers provide drive to three, phase designated transistor pairs of an inverter switching bridge (50) which is supplied power from the rectifier and filter circuit (24).

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Westerville, OH, United States of America

Robert W Baker