Abstract: A toroidal shaped transformer having two levels of structureborne noise isolation is disclosed. A 30-60 dB reduction in noise is achieved by isolation mounting the toroidal transformers coaxially on a central support rod which in turn is supported by an isolation mounted cradle. The isolation layers are made of compliant elastomeric foam rubber material.

Abstract: In a current overload protection circuit, a full wave rectifier bridge circuit is connected between an AC or DC power source to supply AC or DC power to a load through the output circuit of a solid-state relay. A current sensing resistor is connected across the DC terminals of the bridge circuit to sense the magnitude of the current flowing through the load. When an overload fault occurs, the voltage developed across the current sensing resistor will trigger a shunt regulator to turn on an optical isolation circuit, which upon being turned on will discharge a capacitor in an RC timing circuit. The discharge of the capacitor and the RC timing circuit triggers a Schmidt trigger circuit, which cuts off current flow to the input circuit of the solid-state relay, thereby cutting off current to the load. The shunt regulator then turns off de-energizing the optical isolator which, upon being de-energized, causes the current discharge path of the capacitor to be interrupted.