Importance

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Abstract

An electrical protection device for protecting an operating circuit from overcurrent and having relay contacts in series between an electrical power supply and an electrical power load and having a relay coil in parallel across the electrical power supply in an on state. The protection device includes a single relay package having a frame, the relay coil, an armature mechanically actuated from a normally closed contact position to a normally open contact position when the coil is energized, a bimetallic wiper mounted to the armature, a wiper contact mounted to the bimetallic wiper and a normally open contact, a diode connected in series with the relay coil and the normally open contact to pass coil energizing current to the coil from the electrical power supply during the on state and to prevent backflow of coil energizing current to reach the electrical power load when power is first applied to the coil, a first coil lead connected to the relay coil and a second coil lead connected to an anode of the diode, a first contact lead connected to the wiper contact, and a second contact lead connected to the normally open contact. In the on state the relay coil is connected to the electrical power supply through the diode and causes the wiper contact to connect to the normally open contact to connect the supply to the load through the first contact lead and the second contact lead. In the off state the bimetallic wiper responds to an overcurrent in the power supply path by changing shape and moving the wiper contact out of connection with the normally open contact thereby disconnecting the load from the supply.

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First Claim