Friday 7 January 2011

Appliance survey - tumble dryer, washing machine and dishwasher

To gain a better understanding of how to recognise appliances from their power/time signature, I studied the plots of three appliances: tumble dryer, washing machine and dishwasher.

Tumble Drier: (power/time)

The signature is made up of two distinctive sections; the main cycle and the end of the cycle.

During the main cycle, the power draw alternates between 2000 and 200 W over a duration of between 100 and 140 minutes. The reason this is not represented consistently between the plots is due to the periodicity of sampling. Power values are only sampled at minute intervals, so any alternations between samples are not recorded.

The second section constitutes the final sixth of the appliances operation. Although this section is consistent on three of the four graphs, one plot still captures alternation of the power drawn.

Washing machine: (power/time)

This appliance also has two distinct sections; a main cycle and an end section. The main cycle is between 10 and 30 minutes in duration, with a constant power draw of 2000 W. The end period is generally much longer, with an alternating power draw of either 200 or 0 W.

Dishwasher: (power/time)

In this appliance signature, there are four distinct sections; two main washes and two idle periods.

The first main wash takes 25 minutes while the second takes 30 minutes, during both of which a constant power of 1600 W is drawn.

The first idle period lasts 20 minutes during which an almost constant power of 50 W is drawn. The deviations from this power are represented consistently on each of the plots.

Generalising the plots:

The overall shape of each graph containing an alternating power draw is better generalised from a smoothed energy/time graph. This effectively represents an average over the minute interval, instead of samples at minute intervals. An example of a smoothed energy/time graph for the tumble dryer is shown below.

Tumble Drier: (energy/time)

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