Importance

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Abstract

A power supply system for processing current and voltage faults is disclosed. Each phase of a first power source (12) and each phase of a second power source (28) has a pair of switches (60, 64) for controlling the conduction of current from the phase of the power source to a phase load (29). In each of the phases of the first power source (12), a first switch (60) is controlled by a first control signal which has a high level when a voltage fault or current fault condition does not exist. When either a voltage fault or a current fault condition exists, the first switch (60) is turned off. The second switch (64) is turned on by a second control signal during a determination of whether a current fault exists. Furthermore, a logic network causes the first control signal to assume the second level in response to any one of an RMS over/under voltage fault, an instantaneous overcurrent fault, an I.sup.2 t fault, or an instantaneous voltage fault occurring in the phase to which the switches are connected or in any one of the other phases in the first power source. Upon the detection of a voltage fault condition, the first power source (12) is disconnected from the load and a second power source is connected to the load. All of the phases of the first power source are disconnected either immediately in response to the detection of a fault in any one of the phases or, alternatively, the phase with the fault is immediately disconnected and the remaining phases without a fault are disconnected at the zero current crossing points of the AC signal of the phases. The phases of the second source are connected at a point when the voltage of the phase is zero.

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First Claim