I've been learning how microwave ovens work and haven't been able to find any information on the practical way manufacturers create variable power settings.

If I understand magnetrons correctly they are only designed to emit one wavelength/frequency, so is there something I'm missing about how the same wave can just be emitted at a lower power? I was thinking it might be similar to the difference of volts vs amps but that doesn't really explain anything.

Or would one just oscillate power to the magnetron, like a separate duty cycle kind of thing, to lower the average molecular effect?

Really trying to understand the physics of what determines a particular power setting.

  • $\begingroup$ Possible duplicate: cooking.stackexchange.com/questions/7394/… it seems to work in cycles, just vary the on/off timing period for different overall power levels. $\endgroup$ – user108787 Nov 6 '16 at 1:47
  • $\begingroup$ This "possible duplicate" seems to answer it. A separate duty cycle is apparently correct 👍🏻 $\endgroup$ – Jared Rogers Nov 7 '16 at 2:09
  • $\begingroup$ Did you ever put a line of chocolate bars in a microwave, you can see the wavelength. $\endgroup$ – user108787 Nov 7 '16 at 2:14

Most microwave ovens simulate variable power by cycling full power on and off. However, some microwave ovens have truly variable power that is applied uniformly during the entire cooking time. These ovens are sold as having "inverter" technology. What they do is first change the 120 V / 60 Hz input power to something that can be better controlled. Then they use that controlled power to create the microwaves.

Which kind you have matters little when heating large items, but it is easy to see the advantage when trying to heat a small amount of food, especially when it is in small pieces or odd shapes. A normal oven can cause selective overheating, arcing (sparks) or pops, even on the lowest power setting. In contrast, a microwave oven with inverter technology can heat such things without any of these problems. For this reason, I have preferred microwave ovens with inverter technology for many years. For more info, search for "Microwave oven inverter technology".

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  • $\begingroup$ My inverter microwave 1) has at least three hotspots as evidenced by microwaveable popcorn cooked accoring to the popcorn's cooking instructions, I might find more as I continue mapping the interior in an effort to avoid the carbonized corn; 2) has a variable duty cycle at low power settings. At the manufactuer's nominal 35% power it spends about 6 seconds on, 4 seconds off, with the on cycle drawing current equivalent to the nominal 50% power. This is not the only inverter microwave that I have seen that has a variable duty cycle at low powers. $\endgroup$ – Smartybartfast Feb 10 '18 at 4:23

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