Abstract: A circuit and method for regulating power supplied on a network which provides power to an electric arc furnace or other highly variable load. The circuit includes at least a first inverter connected in series with the arc furnace transformer, and in shunt with the power supply. The circuit and method provide an effective, low cost technique for controlling network power.

Abstract: An improved reactance characteristic for an overall ground distance quadrilateral characteristic embodies a particular phase selector, possibly among a plurality of phase selectors and variables, that eliminates undesirable generation of a tripping signal other than only for a selected phase to ground fault. This phase selector is I1FZ1, where Z1 is the positive sequence replica impedance and I1F is the fault component of the positive sequence current component, referenced to the proper phase. Preferably, the pre-fault load current is removed from this quantity. Additionally, an improved restricted phase directional function is implemented, further improving the overall performance of the quadrilateral characteristic relay.

Abstract: A method and apparatus for determining accurate stored energy values and effective DC bus voltage values for a voltage source inverter. The technique includes the determination of an effective DC bus voltage for the VSI based on an output voltage and the modulation index of the VSI. Further, an estimated power flow can be integrated to obtain an estimated stored energy, which can then be used to determine the effective DC bus voltage of the VSI. The disclosed technique is accurate in both transient and steady-state conditions, and reduces the effects of long term error accumulation.

Abstract: A method and apparatus for compensating, consistent with variations in cooling conditions, protection and limit functions of a generator. Limits of the capability curve of the generator, including the overexcited region, underexcited region and region limited by stator current heating, are modified in response to changes in coolant pressure or temperature depending on the type of generator being compensated. Feedback signals and setpoints being provided to fixed protection and limit functions are intercepted and modified in accordance with the relationship between generator rated values and generator performance in view of altered coolant conditions. Protection and limit functions are automatically coordinated. As a result, overall generator performance is improved.

Abstract: A surge suppressor and method for its manufacture. The surge suppressor includes a housing, a plurality of terminal busses contained within the housing, and a plurality of substantially planar conductive plates, each plate having two electrodes for electrical connection to two of the plurality of terminal busses. In one embodiment, by using five terminal busses pentagonally arranged around the plates, the surge protector requires only two types of plate/electrode configurations, thereby simplifying manufacture.

Abstract: A modular control panel for a protective relay. The control panel is removably attached to the housing of the protective relay, and the control panel has a frame which can be arranged to receive a plurality of independently replaceable control panel modules in either a horizontal or vertical orientation. The control panel can be removed from the protective relay housing and remotely mounted, while remaining operatively connected to the protective relay.

Abstract: The method can be performed by receiving at least one sheet and guiding the sheet through an apparatus for cleaning sheet providing tension to the sheet for processing; and processing both planar surfaces of the at least one tensioned sheet.

Abstract: A switch having a contact lever and a compression member connected so as to bias the contact lever into a contact position. The contact lever includes a joint-receiving opening disposed therein. A bearing is insertable into the joint-receiving opening of the contact lever and supports a pivot which forms a connection between the compression member and the contact lever. The joint-receiving opening includes two portions configured one behind the other in the direction of compression of the compression member. The bearing is insertable into the first opening portion in a direction different from the direction of compression and then movable in the direction of compression to produce an interlock connection with the second opening portion of the opening.

Abstract: A 6-axis laser measurement system includes a novel 5-D measurement apparatus and a precision laser roll detector. The 5-D system measures pitch, yaw, X, Y, and Z displacements with a single setup of a laser head and detection housing. The laser roll detector uses a polarizing prism, such as a Glan-Thompson prism, and at least two photodetectors. A linearly polarized laser beam enters the prism, and the beam is split into two polarized components, the intensities of which vary with roll orientation of the detector relative to the polarized laser beam. The outputs of the two photodetectors are connected to the positive and negative inputs, respectively, of a high gain differential amplifier which provides a roll output.

Abstract: A protective relay of the type consisting of a relay contacts controlled by means of a relay coil further includes a pair of triacs controlled by an optical switch. The high speed response is attributed to the configuration of the triacs while high ampere rating is provided by the contacts.

Abstract: A circuit for generating at least two output voltages in response to an input current. A first stage comprises a first impedance for providing a first output voltage when the input current passes through the first impedance. At least a second stage comprises a second impedance coupled to the first impedance, wherein the second impedance provides a second stage voltage when the input current passes through the second impedance. At least a second output voltage is equal to the sum of the second stage voltage and the first output voltage. The second stage further comprises a second stage shunt operable to shunt the input current away from the second impedance when the magnitude of the second output voltage is above a predetermined amount.

Abstract: A modular terminal block for connection between an electrical distribution system and the processing circuitry of a protective relay. The terminal block includes multiple separable tiers, each which is provided with a set of terminal connections and signal contacts. The tiers are of different lengths such that each set of terminal connections are located at different distances from the protective relay to improve accessibility. The terminal block can be mounted in different orientations, and allow shorting between any two adjacent terminal connections.

Abstract: A redundant communications scheme for a protective relay which allows high-speed, reliable, and fault tolerant communications between peer protective devices in a power distribution network. Communications over a selectable primary communication channel are interrupted and switched to a secondary communication channel, which can operate according to a different communication protocol, when a fault is detected on the primary communication channel. The fault detection and switching is performed transparently to the main protective relay processor.

Abstract: A circuit for generating at least two output voltages in response to an input current. A first stage comprises a first impedance for providing a first output voltage when the input current passes through the first impedance. At least a second stage comprises a second impedance coupled to the first impedance, wherein the second impedance provides a second stage voltage when the input current passes through the second impedance. At least a second output voltage is equal to the sum of the second stage voltage and the first output voltage. The second stage further comprises a second stage shunt operable to shunt the input current away from the second impedance when the magnitude of the second output voltage is above a predetermined amount.

Abstract: A control circuit for distributed electrical equipment includes a relaxation oscillator configured for voltage to frequency conversion whereby the output frequency is proportional to the input voltage signal. An opto-coupler provides voltage isolation to the circuit and a standard 8-bit counter translates the frequency signals to a low voltage count data.