A three-phase pump control panel is the interface between the incoming three-phase power and the pump. A pump control panel has four major components that provide four basic functions in a three-phase system. First, the disconnect is the means of disconnecting the pump and its control equipment from the incoming power. Second, the contactor switches the pump on and off as directed by a control device (pressure switch, float switch, timer, etc.). Third, the fuses or circuit breaker are the primary protection for short circuit electrical faults, and fourth, overload devices protect the equipment from being damaged by overload faults. Figure 1 shows a full-voltage start pump control panel. Figure 2 is a schematic for the same panel.
The enclosure - The components providing the four functions listed above are housed in a protective enclosure. One of the primary functions of a pump control panel is to protect you, your customer and the general citizenry from being injured or killed by the high voltage inside of the panel. The safety features of a pump control panel that provide the necessary shock protection are the metal or fiberglass enclosure, the lockable door and the interlock function of the disconnect switch, which keeps the door from being opened when the panel is turned on. Also, most pump control panels manufactured today use “finger safe” components.