Apparatus for controlling the starting of a three phase load with its normal phase sequence

摘要

An apparatus for controlling the starting of a three phase load in its normal phase sequence. The apparatus is connected to the load in a predefined manner and has input terminals for receiving three phase electric energy through external supply lines. There is provided a device within the apparatus which automatically corrects the phase sequence of the electric energy supplied to the load. An open phase protection device is provided which allows the starting of the load in response to the absence of open phase in the received electric energy, and inhibits the starting of the load in response to the presence of open phase in the received electric energy due to, for example, breaking of an external supply line. In one embodiment, the apparatus is built into a submersible motor-pump assembly. The pump is always initiated to rotate its impeller in a proper direction for pumping, regardless of correct or incorrect phase connections between the external supply lines and the input terminals of the apparatus. The open phase sensor and associated switches prevent a single phase mode of operation of the load.