Protecting device for rotating machines

Claim 3

A device as claimed in claim 1, wherein the detector comprises a wide-band transformer having a primary winding and a secondary winding and an insulating capacitor for the DC current connected at each end of the primary winding of said transformer.

Claim 4

A device as claimed in claim 1, wherein said filter consists of a high pass T-shaped network having capacity branches.

Claim 5

A device as claimed in claim 1, comprising, inserted between said filter and said discriminator, an amplifier having an adjustable gain and a full-wave rectifier connected to a resistance-capacity circuit whose charging time constant is less than the discharging time constant.

Claim 6

A device as claimed in claim 1, wherein said level discriminator comprises a threshold regulating potentiometer.

Claim 7

A device as claimed in claim 1, wherein said circuit controlling the supply of the machine comprises a memory detector and a relay whose contacts are inserted in said control and safety circuit Of the supply of the machine.

Claim 8

A device as claimed in claim 6, wherein the memory detector is a thyristor whose control electrode is connected to the output of the level discriminator and whose cutoff is ensured at the end of a given operational time by a delayed control circuit.

Claim 9

An installation for protecting a plurality of rotating machines having each an inductor, an armature and a collector and brushes assembly, against short circuits between the brushes of said machines, said short circuits being usually preceded by damped oscillations of the voltage at the terminals of the armatures of said machines, the repetition frequency of said oscillations increasing immediately before said short circuits, said installation comprising a plurality of protecting devices respectively combined with said machines, each device comprising a detector the input of which is connected to the terminals of the armature or the assembly comprising the armature and auxiliary poles of the corresponding machine, a filter the input of which is connected to the output of said detector for separating the damped electric oscillations from electric disturbances created by the elements of the corresponding machine, a level discriminator the input of which is connected to the output of said filter for producing a logic signal when the frequency of the damped oscillations occuring at the terminals of the armature of the corresponding machine exceeds a given value, and a control circuit connected to the output of said level discriminator for controlling the supply of the corresponding machine, said control circuit being common to all the machines.

Claim 10

An installation for protecting a plurality of rotating machines having each an inductor, an armature and a collector and brushes assembly, against short circuits between the brushes of said machines, said short circuits being usually preceded by damped oscillations of the voltage at the terminals of the armatures of said machines, the repetition frequency of said oscillations increasing immediately before said short circuits, said installation comprising a plurality of protecting devices respectively combined with said machines, each device comprising a detector the input of which is connected to the terminals of the armature or the assembly comprising the armature and auxiliary poles of the corresponding machine, a filter the input of which is connected to the output of said detector for separating the damped electric oscillations from electric disturbances created by the elements of the corresponding machine, a level discriminator the input of which is connected to the output of said filter for producing a logic signal when the frequency of the damped oscillations occuring at the terminals of the armature of the corresponding machine exceeds a given value, and a control circuit connected to the output of said level discriminator for controlling the supply of the corresponding machine, said control circuit being common to all the machines.

Claim 11

An installation as claimed in claim 8, wherein the level discriminators relating to each machine are connected by their outputs to the inputs of an OR circuit whose output is connected to said common circuit controlling the supply.

Claim 12

An installation as claimed in claim 8, wherein each protecting device is provided with a memory circuit for indicating the machine or machines which have started to short circuit.