Abstract: A bank of storage batteries is maintained in a fully charged state by a charging circuit coupled by a controlled, battery energized inverter to AC load lines to which the charging circuit and an AC source are connected. Charging current is controlled in accordance with the load current in the load lines through the primary windings of transformers in the charging circuit and applied to the batteries at a voltage level slightly higher than the full standby battery voltage. Application of full battery voltage to the AC load lines is delayed during a timed start-up period.

Abstract: A bubbler tube is used to sense the liquid level in a wet well. Controls provide a constant flow of air, approximately 11/2 to 1 cubic foot per hour, through the bubbler tube which extends to about 6 inches above the top of the pump suction pipe. The pressure in the pipe is proportional to the height of the liquid above the bottom of the bubbler pipe. A transducer connected in the bubbler system responds to pressure changes in the pipe which are transformed to electrical signals used to control the speed of the pump driving motor. The motor will always drive the pump at a speed which corresponds to the flow coming into the wet well.