Patent ID: 8332980

Claim:
An appliance comprising a drain pump having an impeller and a motor supplied with an alternating supply voltage that drives the impeller, a controller adapted to monitoring a current value supplied to the motor and to control the frequency of the supply voltage among a plurality of predetermined frequencies when the drain pump is operated in a full drainage mode, a storage medium associated with the controller that stores for each predetermined frequency a maximum current value, a minimum current value and an optimal current value; and the controller storing computer implemented instructions that when executed (a) determines if the monitored current value is between the maximum current value and the minimum current value, (b) upon determining that the monitored current value is between the maximum current value and the minimum current value compares the monitored current value with the optimal current value, and (c) adjusts the frequency of the alternating supply voltage among the plurality of predetermined frequencies to cause the monitored current to more closely match the optimal current value.