Abstract:
Automatically changing the tap position in a load tap changer includes noting a polarity of a first tap position of a load tap changer. A duration for which one or more consecutive tap positions of the load tap changer collectively have had the noted polarity also is noted. The one or more consecutive tap positions include the first tap position. The duration for which the one or more consecutive tap positions collectively have had the noted polarity is compared to a threshold value. A change is made from the first tap position to a second tap position with a polarity that is different than the noted polarity when the duration for which the one or more consecutive tap positions collectively have had the noted polarity is longer than the threshold value. A change may be made from the second tap position back to the first tap position.
Abstract:
A relay (70) includes contacts (73) residing within a glass tube (72). A coil (76) surrounding the tube (72) and a switch (66) are connected in parallel between two terminals (77) of the relay (70). A current source supplies a current to the coil (76) and switch (66). When the switch (66) is open, substantially all of the current passes through the coil (76) and the coil (76) produces a sufficient amount of magnetic flux to close the relay's contacts (73). When the switch (66) closes, it shunts a sufficient amount of the current away from the coil (76) to reduce the magnetic flux it produces below the level needed to keep the contacts (73) closed. The current source is sized so that the coil (76) requires relatively few turns, thereby allowing the relay (70) to be relatively thin. The coil (76) is formed by a conductor (140) embedded in an insulating substrate (128) surrounding the tube (72).
Abstract:
A first and a second line (L1, L2) conduct the input direct voltage (Ue) to the load. A fuse (S) is connected in series in the first line. The switching contact (K11) of a first relay (K1) is also connected in series in the first line and is opened during a disconnecting operation. The switching contact (K21) of a second relay (K2) is connected in parallel between the first and second line after the first relay and is closed during a disconnecting operation, after the first relay has been opened. The inventive device is very fault-tolerant, even with usual commercial relays.
Abstract:
A preventive maintenance tapping technique includes noting a tap position of a load tap changer and noting a duration that the tap position has been held. The duration that the tap position has been held is compared to a threshold value, and the tap position is changed if the tap position has been held for longer than the threshold value. Similarly, a duty cycle monitoring technique for monitoring life of load tap changer contacts includes detecting an arcing event. Arcing surfaces involved in the arcing event are identified and the effects of the arcing event on the arcing surfaces are calculated. Estimates of the erosion on the arcing surfaces are updated, and the estimates are compared to a threshold value. A signal for maintenance is generated when the estimate exceeds the threshold value.
Abstract:
A micromachined magnetostatic relay or switch (100) includes a springing beam (105) on which a magnetic actuation plate (120) is formed. The springing beam (105) also includes an electrically conductive contact (115). In the presence of a magnetic field H, the magnetic material causes the springing beam (105) to bend, moving the electrically conductive contact either toward or away from another contact, and thus creating either an electrical short-circuit or an electrical open-circuit. The switch (100) is fabricated from silicon substrates and is particularly useful in forming a MEMs communication and control circuit for a miniaturized DC motor.
Abstract:
A Positive Temperature Coefficient Resistivity (PTC) element has a resistivity that increases as the temperature increases. Circuit breakers having PTC elements can achieve better overload and short circuit protection than existing products. Breakers with PTC elements can also be combined with ground fault detection circuits to activate the circuit breaker under ground fault conditions that are less severe than the overcurrent conditions that would normally activate the circuit breaker. A shunt trip assembly incorporating a PTC resistor reduces the required power rating of the clearing switch.
Abstract:
In accordance with aspects of the present invention, a power control circuit includes a MAIN window comparator circuit providing a MAIN signal; an AUX window comparator circuit providing an AUX signal; a state machine receiving the MAIN signal and the AUX signal; a MAIN slew circuit coupled to drive a MAIN switch, the MAIN switch coupled between MAIN and an output; an AUX slew circuit coupled to drive an AUX switch, the AUX switch coupled between AUX and the output; wherein the state machine operates to continuously activate either the MAIN switch or the AUX switch according to the MAIN signal and the AUX signal such that the output is continuously coupled to either a MAIN input or an AUX input with minimum disruption to output voltage, input and output capacitance inrush currents or reverse conduction. What really makes the circuit unique is it is combined with an adjustable forward biased rectification circuit for each channel of MAIN and AUX.
Abstract:
Systems and methods presented herein generally provide for the controlled voltage of electrical energy through the selected operation of power stages. In one embodiment, a system that provides electrical energy includes a power supply and at least two power stages coupled to the power supply. The power stages are operable to selectively output electrical energy. By selecting the number of power stages which are turned on at a given time the total voltage of the electrical energy is controlled at that time. The use of air core magnetic flux coupling provides a unique, easily insulated method to provide power to the voltage stages at different potentials relative to each other. The system may further include one or more controllers coupled to the power stages to control selection of the power stages and thereby vary the output voltage.
Abstract:
A proportional actuator (10) for proportional control including a saturation tip (24) formed on the movable armature (16) for movement within a step-wound coil (18). The coil providing clearance for the saturation tip, allowing the coaxial diameters of a magnetic pole piece (14) and the armature. The configuration of the armature provides significantly higher magnetic force attraction between the magnetic pole piece and the armature because of the increased coaxial diameters of the armature and the pole piece. In addition, because of the increased diameter of the armature, the surface area of the armature that is exposed to the saturation tip is increased, thereby increasing the amount of flux that is coupled to the magnetic pole piece by the saturation tip. The proportional actuator is described with reference to applications in proportional control valves. Highly preferred embodiments of the proportional control valve include a damping mechanism for minimizing overshoot by providing restricted fluid flow path between the magnetic pole piece and the armature and tank pressure for fluid being supplied to or removed from the apparatus being controlled by the proportional control valve.