Powerware Corporation

General Signal Corporation

Best Power Technology, Inc.

Renaissance Learning, Inc.

Donald K Zahrte, Sr

Frederick A Stich

David L Layden

Peter William Jungwirth

Douglas C Folts

Craig Edevold

Thomas G Hubert

Cary Frank Winch

Joseph R Wade

Edward Gerard Beistle

Richard V Baxter, Jr

Mark R Swanson

Gregory C Kohls

William C Apperson

William J Hazen

Glenn A Koosmann

Derek Laufenberg

Juan M Medina

Robert R Davidson

An electrical cabinet for an uninterruptibe power supply (UPS) system includes universal slots that can receive power modules, battery packs, or chargers. The back plane of the slot has connector terminals for battery packs and power modules. The cabinet can be easily reconfigured as desired by changing the number of power modules chargers or battery packs installed. Circuitry is provided that indicates the capacity and operational readiness of the cabinet. This circuitry monitors the battery packs in each slot, and isolates any detected fault to a particular pack.

System for detecting defective battery packs

A device and method for reading optical marks are disclosed. The device, an optical mark reader (OMR) has an array of photo sensors with light-emitting diodes (LEDs), which are driven by digital-to-analog converters (DACs), which are in turn controlled by a microcontroller. When calibrating the OMR, the sensors read a white card, and the microcontroller adjust the DACs so that the outputs of all sensors are at a voltage close to the saturation points of the photo-transistors in the sensors so that the maximum useable ranges of the sensors are utilized. The sensors then read one or more patterns of known grayscales and their response voltages are recorded. The microcontroller generates an array of voltage values as a function of grayscale for each sensor and store the values in a memory device. When reading an optical marks, the sensor output voltage in response to a mark is looked up in the table of voltages values stored in the memory device to determine the grayscale of the mark. Various algorithms may be employed to calculate an apparent grayscale to allow the test taker's true intent be ascertained without requiring the test taker to make a perfect mark.

Device and method for inspecting markings

A charging control circuit for severe battery conditions and an uninterruptible power supply (UPS) system including same are presented. The charging control circuit utilizes both hardware and microprocessor control to allow the UPS to start with depleted or no batteries installed. Initially, the hardware control loops regulate DC bus voltage generation to charge the batteries to a safe level to allow the UPS housekeeping circuitry to wake up and assume control of the UPS operation. Once the microprocessor has awoken, it assumes control of the DC bus and charging of the batteries. If no batteries are installed, the hardware control loop utilizes a fast responding voltage mode control to regulate the DC bus, while a microprocessor-based current mode control is used when batteries are installed. Hardware over voltage control and microprocessor shut off control is also provided.

Battery charger control circuit and an uninterruptible power supply utilizing same

A modular uninterruptible power supply is presented having multiple power modules installed therein. Each of the individual power modules contains an internal bypass circuit sized for its particular power module. Preferably internal bypass circuitry is sized to carry two per unit load. The system and method of the invention also includes internal control circuitry for each of the modular power modules that control transitions between the inverter and bypass modes of operation. This transition control is coordinated with the other controllers for the other modular power modules installed in the uninterruptible power supply. Both the high speed communication bus and a high level interrupt line are utilized to minimize the transfer break time between different modes of operation while ensuring that the inverter is never paralleled with the utility line voltage. To further minimize this transfer time, a solid state switching circuit is utilized to provide the initialization between operational modes. To maximize the efficiency during the bypass mode of operation, and electromechanical relay is utilized in coordinated operation with the solid state switching device to provide long-term power requirements during the bypass mode.

Distributed internal fault bypass in a modular uninterruptible power supply

Presented is a center switching circuit and an inverter and an uninterruptible power supply (UPS) utilizing same. The center switching circuit selectively enables and disables power flow to and from the bus capacitors of an inverter or UPS. As such, the center switching circuitry effectively removes the bus capacitors from the circuit. This allows operation of the inverter or UPS in a high efficiency mode whereby input line voltage may be passed essentially without compensation to the output when the center switching circuit is open. Modulation of the center switching circuit during this mode provides soft charging of the bus capacitors so that they are available to source current in a double-conversion or DC boost mode upon degradation or loss of the line voltage. To supply output power from the bus capacitors, the center switching circuit is closed to associate these capacitors with the neutral. Fault isolation is provided during operation by opening the center switching circuit to prevent power flow from the bus capacitors.

Inverter having center switch and uninterruptible power supply implementing same

A line-interactive single conversion uninterruptible power supply (UPS) utilizing a multiple tapped ferroresonant transformer and a square wave PWM inverter is presented. During normal utility line operation, the line voltage is not modified in any way, except for ferroresonant filtering and regulation. Tap control circuitry insures proper tap selection based on the utility input voltage. During tap transitions in utility out of specification operation, a second power source, such as an inverter, is operated to provide output power to the connected loads. The control of the inverter switching angles may be accomplished through a look-up table. This look-up table contains the converter pulse widths for monitored battery voltage. No output voltage feedback is required. Based on the inherent regulation provided by the ferroresonant transformer, the PWM control may be accomplished in course steps.

Uninterruptible power supply and ferroresonant transformer for use therewith

A standby power system is provided having power conversion, output voltage control, and line-fault detection systems that make possible a significant reduction in the cost of the system. The standby power system provides backup power to a load, such as a computer system, when main AC line power fails. A system DC battery voltage is converted to an AC output voltage signal at line voltage levels by a power conversion system including a high frequency push-pull inverter, a light-weight low-cost high frequency transformer, a rectifier, and a line frequency inverter. The high frequency inverter is controlled to provide high frequency battery voltage pulse bursts separated by low frequency zero voltage dead times which are boosted by the transformer to line voltage levels and rectified by the rectifier. The line frequency inverter is controlled to provide the rectified line voltage level pulse bursts to the standby power system output in the form of a stepped square wave output signal at line frequencies. Rms and peak output voltage control is provided by a system controller based on a single digital output voltage control signal. The system controller detects the occurrence of AC line faults using a single digital line sense signal. Since analog-to-digital conversion of the power system input and output voltage waveforms is not required for line fault detection or output voltage control, the system controller may be implemented using a low-cost microprocessor.

Standby power system

Instabilities in the output voltage provided from an AC power supply system such as an uninterruptible power supply connected to a power factor correcting load are suppressed by a dynamic voltage regulation stabilizer system which is connected across the output lines from the power supply system to the load. The DVR stabilizer system includes a rectifier connected to the power supply system output lines. A capacitor is connected across the output nodes of the rectifier. Switching devices form a bridge that connects the capacitor to the output lines. Selected switching devices in the bridge are turned on for a selected duration encompassing the time of the peak of each half-cycle of the AC voltage waveform provided by the power supply system. During normal operation, where the peak AC voltage from the power supply system is substantially constant, the capacitor charges up through the rectifier to a voltage level near the peak value of the AC voltage waveform. When the peak AC voltage level rises above the normal peak level, the capacitor clamps the voltage across the output lines at a value near the steady state peak value. When the peak voltage level drops below the normal peak value, the capacitor discharges through the switching device bridge during the peak of the half-cycle to fill in for the voltage drop. The DVR stabilizer system thus reduces the effect of interactions between the power supply system and the PFC load, to thereby dampen oscillations and stabilize the AC voltage waveform.

Dynamic voltage regulation stabilization for AC power supply systems

An uninterruptible power system has a transformer with a primary connected to input terminals, a secondary connected to output terminals, a static switch connected between the input terminals and the primary, and an auxiliary primary connected to an inverter which is supplied by a battery to provide output voltage to the output terminals when a main AC power system connected to the input terminals has failed. The primary has multiple taps at different voltage levels and a buck-boost winding. The taps of the transformer are switched and the buck-boost winding is controlled to provide either buck, boost, or pass-by to allow control of the output voltage from the transformer to within a few percent of a desired voltage level despite large changes in the input voltage. A battery charger coupled to the auxiliary primary operates as a boost converter to provide current to charge the battery at a current level which tracks the input voltage from the AC power system, thereby providing a substantially unity power factor to the AC power system. The voltage control of the output voltage also controls the voltage at the output of the auxiliary primary to which the battery charger is connected, whereby the voltage applied to the charger is substantially regulated and the output power of the charger itself is substantially regulated. The charger can be operated in programmable modes to provide a desired charge configuration for the battery. Detection of faults in the AC power system is enhanced by accurate detection of the zero crossings of the input voltage from the AC power system, and by comparison of the AC input power waveform with an adaptive reference.

Uninterruptible power system

A back-up uninterruptible power system has a power supply path from input terminals connected to AC power system lines to normally supply power to a load. Upon the occurrence of a line fault, a static switch in the power supply path interrupts the connection between the AC power lines and the load and an inverter is turned on to provide power derived from an auxiliary battery through a transformer to the power supply path to supply AC power to the load. By using the static switch, switching from line connection to backup power can be done quickly, within a half cycle, so that substantially no interruption of the output waveform is observed. The inverter can be operated to provide a commutation pulse to the SCRs in the static switch to commutate an SCR which might otherwise continue conducting after the triggering signals to the gates are cut off and before the inverter supplies the AC power to the load. A relay connected between the input terminals and the static switch is controlled to open relay contacts after the static switch has interrupted the current flow to the load, thereby providing positive electrical isolation of the AC power system from the uninterruptible power system while allowing the mechanical relay contacts to switch only during times of no current. Line fault detection is carried out by creating a digital waveform composed of an average of prior cycles of the AC input waveform, converting the stored waveform to an analog signal, and comparing it with the present input signal in phase lock therewith to detect deviation of the input signal from the reference waveform.

Growing community of inventors

Necedah, WI, United States of America

Donald K Zahrte, Sr