An appliance for washing objects in which is employed a pump system for varying the spray velocity of washing fluid dispensed from spray jets affixed at an angle relative to a spray arm. In one embodiment, the pump system includes a pump having a pump motor such as a synchronous motor responsive to a variable frequency, single-phase alternating current input. The pump system also includes a pump motor control circuit configured to vary the frequency and voltage of the input, which in one example effectuates changes in the rotational speed of the pump motor in accordance with one or more operational cycles. The pump motor control circuit incorporates in one example a rectifier and an inverter that permits operation of the appliance when coupled to supply mains.