US Patent 9935495 Automatic transfer switch

Automatic transfer switch for switching an electrical load between two power sources. In one example, the automatic transfer switch includes four latching relays and an electronic controller. A first power source line connection is connected to an electrical load line connection via a first latching relay. A first power source neutral connection is connected to an electrical load neutral connection via a second latching relay. A second power source line connection is connected to the electrical load line connection via a third latching relay. A second power source neutral connection is connected to the electrical load neutral connection via a fourth latching relay. The electronic controller connects the second power source to the electrical load when a voltage of the first power source is less than a first threshold, and connects the first power source to the electrical load when the voltage is greater than a second threshold.