Abstract: Electrical equipment (14) is safeguarded from damage due to parallel arc faults by a circuit that provides several levels of protection. A semiconductor switch (18) and a current sensor (24) are placed in series with the electrical equipment (14). When the current to the equipment exceeds a first threshold for a predefined period of time, the semiconductor switch (18) is rendered non-conductive until the circuit is specifically reset. When the current to the equipment exceeds a greater second threshold, a pulsed signal alternately places the semiconductor switch (18) in conductive and non-conductive states so that the average current applied to the equipment (14) is within an acceptable level. The pulses are measured to determine whether a parallel arc fault has occurred. When the measured pulses (74) are within a predetermined range, a parallel arc fault is declared and the semiconductor switch (18) is rendered non-conductive.

Abstract: Electrical equipment (14) is safeguarded from damage due to parallel arc faults by a circuit that provides several levels of protection. A semiconductor switch (18) and a current sensor (24) are placed in series with the electrical equipment (14). When the current to the equipment exceeds a first threshold for a predefined period of time, the semiconductor switch (18) is rendered non-conductive until the circuit is specifically reset. When the current to the equipment exceeds a greater second threshold, a pulsed signal alternately places the semiconductor switch (18) in conductive and non-conductive states so that the average current applied to the equipment (14) is within an acceptable level. The pulses are measured to determine whether a parallel arc fault has occurred. When the measured pulses (74) are within a predetermined range, a parallel arc fault is declared and the semiconductor switch (18) is rendered non-conductive.

Abstract: A normally ungrounded power system for a oil well is provided which includes a power transformer above ground and a pump motor below ground. There is provided a signal system which includes a below ground sensor system and an above ground signal conditioning and monitoring unit where the sensor system utilizes the main power lines for carrying the sensor signals. A connectable high resistance grounding scheme is provided to the aforementioned floating system, so that in the event of a arcing ground fault or similar occurrence the system may be immediately grounded, thus compensating for the effects of the arcing ground fault and providing personnel safety and electrical equipment protection. When the high resistance grounding system is not utilized the aforementioned signals from the sensors are easily carried by the power conductors.

Abstract: A method and a circuit for motor field regulation in the constant horsepower speed range, wherein the weakening of field current allows operation of the motor at speeds higher than the base speed while maintaining rated armature voltage. The field current is weakened in response to speed feedback signals to provide a rapid response in controlling field current. The motor field is also regulated in response to a counter-EMF and IR compensation circuit to further weaken the field current, where the counter-EMF developed in the DC motor would cause excessive voltage across the armature.