Abstract: A monitoring device for semiconductor rectifiers which are located in a three-phase current bridge circuit, in which the bridge circuit is provided with two semiconductor rectifiers per rectifier branch, including a current-sensitive detector circuit connected to each pair of semiconductor rectifiers of each branch through a resistor, wherein when the semiconductor rectifiers are intact, the sum of all current flowing through the resistors is zero, as detected by the current-sensitive detector circuit.

Abstract: A circuit for protecting an AC driven load that is controlled by a solid state device, such as a triac, or inverse SCR's, or the like. Whenever the AC power output of the control is asymmetrical to the load, the circuit produces a signal capable of shutting down the AC power to the load, sounding an alarm, switching to a different controller, or signaling another load protecting reaction. The protection circuit continuously measures each individual half cycle of the AC output from the controller to the load and provides for phase shifting about a reference point, resulting in summing (or nulling) of the AC output half waves (positive and negative) at the reference point. The summing (or nulling) reference point is coupled to the gate of a switching element connected across the AC input line, the switching element being responsive to a positive or negative voltage above a predetermined threshold value.

Abstract: A transistorized detector sensitive to the ripple component of the DC output of an alternator gives a visual or audible warning signal when the ripple component exceeds a predetermined level providing early indication of failure of either a winding or rectifier diode.

Abstract: A circuit arrangement for monitoring the current inbalance in two parallel-connected converter branches, each of which includes at least two series-connected converter valves. The anodes and cathodes, respectively, of adjacent converter valves in a given branch are connected together via cross-connections containing current transformers. A differential current transformer is provided at the output junction point of the two converter branches. Starting with the output signal of the differential current transformer, the exact current misdistribution for each adjacent converter valve pair is determined via summing amplifiers by adding the currents of the transverse transformers. A protective measure is triggered if a current misdistribution occurs.

Abstract: A circuit for detecting the shorting of a diode in a circuit for rectifying AC current. A current transformer senses the current flowing through a diode. A DC bias current applied to the transformer secondary winding along with the unidirectional pulses normally passed by the diode cause saturation of the transformer core so that the normal current passed by the diode does not induce corresponding pulses in the secondary winding. In the event of diode shorting reverse current pulses will produce corresponding pulses in the secondary winding and those pulses are detected by a relay so that relay actuation occurs upon diode shorting.

Abstract: A circuit for detecting a failed diode in a multiple diode rectifier bridge detects open or shorted diodes in both multi-phase, half-wave rectification and single or multi-phase full wave rectification arrangements and provides a failure signal for sounding an alarm or tripping the circuit to protect the load or power source as the case may be.

Abstract: An apparatus for detecting each short circuited diode in a plurality of diodes, coupled in a parallel combination, is disclosed. The apparatus utilizes a flashing light emitting diode to indicate whether the particular diode under test is shorted or not. By utilizing the series inductance associated with each diode circuit, effective isolation of the particular diode under test is obtained for a short duration test pulse and allows the appropriate test to be made.

Abstract: A shorted diode in an array of parallel diodes is detected by connecting between normally equipotential points in each pair of adjacent branch circuits of the array an inexpensive indicating device comprising signaling means for visually indicating that a malfunction has occurred if appreciable current flows in an associated resistor. The signaling means comprises heat sensitive material that changes appearance when its temperature is raised to a predetermined high degree by the heat generated in the resistor when current flows between the aforesaid connection points due to the potential difference that develops therebetween as a result of a diode failing shorted.

Abstract: A thyristor fault-detecting apparatus comprises a thyristor bridge with A.C. terminals connected to a three-phase A.C. power supply and having six thyristor arms, and an inductive load connected to D.C. terminals of the bridge. Each of the A.C. paths has a saturable reactor with an output winding so set as to be excited by the line current within the range from .pi./3 to 2.pi./3 (rad). Output voltages of the reactors are rectified and added, so that a fault in the thyristor is detected by the disappearance of the added output.

Abstract: To detect system ground faults and shorted alternator output winding turn-to-turn faults, the series combination of a resistor and the operating coil of an electrical relay having a normally closed contact pair is connected between the neutrals of two parallel connected polyphase alternator output winding groups, the junction between the resistor and operating coil is connected through a resistor to ground and the normally closed relay contact pair is connected in series in the alternator exciting field winding energizing circuit. To detect open diodes in the main polyphase diode bridge type full-wave rectifier circuit, an auxiliary polyphase full-wave rectifier circuit having the operating coil and normally closed contacts of two relays in series in each leg is provided. Upon the failure of a diode of the main rectifier circuit, sufficient current to operate the corresponding relay in the auxiliary rectifier circuit is diverted therethrough.