Microwave oven power granularity

Index, feed.

Most microwave ovens let their user set a power level between 10% and 100% in 10% increments. However, it seems that there is no such thing as a partially-on magnetron; it's either full-on or full off.

I measured the power consumption of my microwave oven every second over one-minute periods with all the available power settings. The data confirms that the consumptions is either 1440W (full-on) or 38W (idle); intermediate values are rare.

The graphs below use a cutoff of 200W to decide whether to consider the oven on or off. The duty cycle computation uses the actual, non-boolean power values, which explains why they do not fully match the graphs.

Power level: 10%

Power (W): min = 37, max = 1325; duty cycle: 5.2%; n = 61

Power level: 20%

Power (W): min = 35, max = 1451; duty cycle: 18.0%; n = 62

Power level: 30%

Power (W): min = 34, max = 1421; duty cycle: 28.5%; n = 61

Power level: 40%

Power (W): min = 37, max = 1420; duty cycle: 36.7%; n = 61

Power level: 50%

Power (W): min = 32, max = 1444; duty cycle: 46.9%; n = 61

Power level: 60%

Power (W): min = 37, max = 1365; duty cycle: 59.2%; n = 62

Power level: 70%

Power (W): min = 37, max = 1373; duty cycle: 71.8%; n = 61

Power level: 80%

Power (W): min = 37, max = 1395; duty cycle: 78.8%; n = 62

Power level: 90%

Power (W): min = 37, max = 1429; duty cycle: 87.5%; n = 62

Power level: 100%

Power (W): min = 203, max = 1465; duty cycle: 94.3%; n = 61

Conclusion

Measurements confirm the popular belief that microwave ovens adjust power by alternating idle and fully-on periods, over durations of several seconds. In the case of my oven specifically, cycles last about thirty seconds. This means that heating something up at 10% for thirty seconds will not give the expected equivalent of three seconds of energy.

Data

File of JSON lines: microwave-oven-power-all.json.

www.kurokatta.org

David Haguenauer <www@kurokatta.org>
$Id: microwave-oven-power.malblog,v 1.8 2018/08/07 04:28:03 homer Exp $