Abstract: A dual resistance heater for a phase change material region is formed by depositing a resistive material. The heater material is then exposed to an implantation or plasma which increases the resistance of the surface of the heater material relative to the remainder of the heater material. As a result, the portion of the heater material approximate to the phase change material region is a highly effective heater because of its high resistance, but the bulk of the heater material is not as resistive and, thus, does not increase the voltage drop and the current usage of the device.

Abstract: A method is provided for interconnecting a single electrical heating element of a hot water heater to first and second AC electrical power sources. Typically, these first and second AC electrical power sources include a utility provided electrical power source and a renewable power source that generates AC power from DC power. The method includes operating a controller that selectively connects and disconnects the first and second power sources. If sufficient electrical power is available from the renewable power source, the utility provided electrical power source may be disconnected to preferentially utilize renewable energy.

Abstract: The present invention provides system for testing an electrical winding element that is usually a stator bar or a stator winding. The stator bar is attached to a short circuit conductive element to form a closed short circuit of a single turn that acts as a primary circuit. The closed short circuit is connected to a step-up transformer that will act as a secondary circuit and which has at least two turns. The step-up transformer uses a controlled variable voltage source that charges the closed short circuit. Charging the closed short circuit creates a current in the stator bar inner conductive element, causing heat on the stator bar by induction. The system of the present invention is suitable for an accelerated thermal aging test that simulates closely how heat is created by induction on stator bars of electric machines.

Abstract: Protection systems are described for electrical systems such as electrical arc furnaces. The protection systems may be designed and used to detect and clear faults that may occur within the electric arc furnace. For example, a pair of Rogowski coils may be used to detect current at their respective locations along a conductors, and output corresponding signals to a multi-function, differential relay having multiple voltage and current inputs. By comparing the signals from the Rogowski coils, the differential relay may determine whether a fault exists at some point along the conductors and between the pair of Rogowski coils. Further, the relay may then, in response to the fault, trip a circuit breaker or other network protection device, so that the fault may be corrected.

Abstract: In order to refine a method for electric heating of furnaces for heat treating metallic workpieces, especially vacuum furnaces usable for plasma carburizing or nitriding, in which the heater elements of a furnace are supplied with a heating voltage that is generated in the secondary circuit of a three phase transformer connected to the three phase power network such that a comparatively small reactive power component can be obtained in a simple and economical manner, it is proposed that the primary coil windings of the three phase transformer be switched in the delta connection during a first heating phase and in the star connection during a second heating phase, whereby the switchover time from the delta connection to the star connection is determined as a function of operating parameters characteristic for the heating process.

Abstract: The bead source for the thermionic detector of a gas chromatograph is heated by the secondary winding of a transformer having a center-tapped primary and operating in the push-pull configuration. The voltage drop across the bead is compared with a preselected reference voltage and an error signal is generated. The error signal is used to control the output of a pulse width modulation control which supplies the transformer primary winding.

Abstract: A method and apparatus is disclosed for transferring electrical power to a balancer 14 without the need for a physical connection between the balancer and the power source 16 or the controller 12 and which also provides for data communication between a balancer 14 and a balancer controller 12.

Abstract: An electrical control system for an electrically heated window in a motor vehicle has a voltage source including a generator, a voltage regulator for regulating a generator output voltage, a transformer switched between the generator and a heating window, the generator output voltage being increased before supplying to the heatable window, and a unit for measuring a temperature of the transformer and interrupting a communication between the transformer and the voltage source in the event of exceeding an adjustable limiting temperature.

Abstract: A circuit arrangement for control of the temperature of a heating element adapted for contact by a material to be heated includes a transformer wherein the secondary winding is a metal ring which is the heating element with a temperature detection winding provided on the core of the transformer. An electronic switch and current sensing means are connected to the primary. A comparator, which receives input signals from the current sensing means and temperature detection winding, is operatively connected to the electronic switch to control its operation.

Abstract: A proximity effect heat-tracing system in which proximity effect heat-tracing circuits are fed in either direction from a plurality of feed points connected to a single main transformer to increase the length of pipeline supplied by a single main transformer. A secondary transformer interposed between a main transformer and a plurality of feed points reduces the voltage required to be applied to a proximity effect heat-tracing system of a given length. Two or more proximity effect heat-tracing systems used along the same length of pipeline, employ neutral conductors having approximately the same diameter as "hot" conductors where the secondary of the main transformer in each system is 180.degree. electrically out of phase with the secondary of the main transformer in the other system.

Abstract: Methods and apparatus for detecting abnormalities in proximity effect pipeline tracing circuits by coupling conductive elements carrying proximity effect circuit currents and having opposite polarities. These conductive elements are coupled to an additional conductive element which is in turn connected to a system for detecting current so that when the difference between the proximity effect circuit currents is non-zero, the current flows through the additional conductive element and is detected by a relay or ammeter.

Abstract: A heating power supply apparatus for polycrystalline semiconductor rods, including a power transformer and anti-parallel thyristor unit groups connected to respective portions of the secondary of the power transformer, balance transformer groups connected to the anti-parallel thyristor groups and combined to make constant a secondary current of each of the balance transformers, and semiconductor rod connecting terminals connected to the secondaries of the balance transformer groups, respectively. The balance transformer groups are divided into a group of plural balance transformers of small current and high voltage for exclusive use during the starting and a group of plural balance transformers for taking over operation from the group of balance transformers of small current and high voltage and continuing subsequent operations.

Abstract: A plurality of zones of an induction heating coil are individually controlled by varying the current through one or more zones of the coil to obtain a desired temperature profile in a workpiece. The current flow through a zone of the coil is determined by the conduction state of an associated saturable reactor, which is controlled in accordance with a preselected value or a variable value generated, for example, by a computer.

Abstract: A circuit is described for controlling voltage input to a pair of resistances. A main transformer and variable auto transformer are wired in cascade between the voltage supply and the resistances. The resistances are wired in series to the output of the variable auto transformer, with the null point between the resistances being connected to the variable tap of the auto transformer.

Abstract: Temperature responsive power supply apparatus for electrical resistance heating, e.g. for weld stress relief, has a power supply transformer comprising first and second secondary windings in series with one another and first, second and third conductors for connecting the secondary windings to heating elements. A pair of temperature sensors provide temperature signals corresponding to the temperatures of heated zones heated by the apparatus, and a pair of control units responsive to the temperature signals control the current flow through the conductors. A switch enables one or both control units to regulate saturable reactors or the like in series with the conductors, whereby the control unit can regulate two respective heating circuits each including one of the secondary windings or one of the control units can regulate a heating circuit including one or both of the secondary windings. The apparatus provided improved versatility for heating one or more large or small pipe welds.

Abstract: A detecting circuit comprises a magnetic core having a rectangular magnetic characteristic, a first winding coupled magnetically to the magnetic core, for applying a current to be detected, and a second winding coupled magnetically to the magnetic core, for applying a reference current. An output signal is derived from the second winding.