Cutler-hammer, Inc.

Eaton Corporation

John A Rauenbuehler

Robert O Graham

Albert C Snowdon

An electric power switch or contactor of the 3-pole AC type or the like is provided with means making it capable of withstanding higher fault currents such as short circuit currents. This is done by providing the insulating contact carrier with integrally molded stops that will allow the spring-biased bridging contacts to be blown slightly open by the high electro-dynamic forces occurring during high fault currents but will limit such opening of the contacts to gaps small enough to inhibit the arc from moving from between the contacts. Instead of attempting to keep the contacts closed under such conditions which would require a large magnetic force, allowing the contacts to open this small amount eliminates the need for a larger magnet, reduces the blow-open force and, more importantly, the small gaps will retain the arcs between the contacts and will inhibit them from flashing out to other parts of the contactor with consequent burning and destructive effect. As a result, the device will remain reusable with replacement of the contacts and possibly only minor repair.

Contactor having higher fault current withstandability

A unitary three-phase current transformer having its three iron cores and three secondary coils enclosed and retained in their positions by a pair of like molded housing halves. The housing halves also have pairs of juxtaposed slots in their upper, adjacent edges for clamping pairs of secondary coil terminal inserts therebetween to mount the same so as to allow connection of the secondary coils to external conductors. The housing halves are connected together by symmetrically arranged sets of screws with the screws of each set extending through holes in the respective half and threaded into the respectively opposite half. The asembled housing halves provide three apertures through which are inserted respective bus bars serving as one-turn primary windings. A terminal strap is attached to one end of each bus bar, the bus bar is inserted through the aperture, and the other terminal strap is attached to the other end thereof. The housing halves also have slots defined by pairs of lugs through which screws extend rigidly to fix the two outer bus bars thereto, the terminal straps serving as both mounting means and electrical connecting means for the transformer.

Three-phase current transformer

A method of making electrical contacts of the type having a pair of disk-shaped contacts of precious metal secured to an electrically conductive base member. In this method, continuous flat silver strip is first preformed in a punch press to provide a series of disks left connected to one another at their opposite peripheral edges to afford sufficient stiffness for handling. A pair of these strips are then fed, while maintaining registration therebetween, concurrently with a continuous base member into a brazing or welding machine and are secured to one surface of the base member adjacent opposite edges thereof to form a continuous subassembly strip. This subassembly strip is then fed into a cut-off device with accurate registration so as to make cuts through the connection exactly between adjacent disks of directly opposite pairs thereof and through the base member to provide two round contacts spaced apart on a rectangular base member. These round contacts of diameter X require substantially less silver than square contacts having a side dimension X while providing an electrical life the same as the larger area square contacts. This method combines the advantages of the continuous attachment process with the economy of discrete contacts.

Growing community of inventors

New Berlin, WI, United States of America

John A Rauenbuehler