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Can anyone here explain to me why microwave ovens always have their power settings as multiples of some value, e.g. 200/400/800w but never have the ability to s

by jahnu 11y ago

Can anyone here explain to me why microwave ovens always have their power settings as multiples of some value, e.g. 200/400/800w but never have the ability to set a specific power output, e.g. 425w.

trymas 11y ago
Microwaves with turning knobs (example [0], maybe not the best, but you'll get the point) can have arbitrary power setting. My personal, electronic microwave, has values 125/250/500/750W so not completely exponential (I guess, that's what you meant?). One thing is, you can always (?) set arbitrary time, so you can compensate to gaps in power settings. Other thing, maybe electronics are more simple with power settings like these? When I see exponential settings I would always think of analogy to photography and 'f-stops' [1]. Some devices have exponential settings due to the physical nature of something, but is it the case with microwaves, I don't know. [0] http://www.firstiraq.com/sites/default/files/products/5002-1_neu.jpg http://www.firstiraq.com/sites/default/files/products/5002-1... [1] https://en.wikipedia.org/wiki/F-number https://en.wikipedia.org/wiki/F-number
- jahnu 11y ago
  Yeah I was wondering if it was analogous to transformers where you have multiple coils all wound together and you combine them in various ways to get different voltages. I have almost no idea how a magnetron actually works.
rainforest 11y ago
At a total guess it's down to the lack of precision in the output at anything other than full power. Most (all?) microwaves just pulse the magnetron to achieve an average delivery of the rated power so the difference between 400W and 425W would be dependent on the time the microwave runs, given most tend to use a fairly long time period. You can see this effect if you run a microwave on low power for a short period - sometimes the magnetron will be running for the full duration.
skykooler 11y ago
Microwave ovens use magnetrons to produce the microwave radiation. Magnetrons cannot be run at anything less than full power. Some microwaves have additional coils in the magnetron that can be connected to increase the power level, but it's limited to the power levels you can get from the various combinations of coils. For the same reason, running a normal microwave at "50% power" actually means it runs at full power for several seconds, then switches off for several seconds, then repeats. The pulses are so long because starting and stopping are hard on the magnetron.
- Grishnakh 11y ago
  This isn't true, if you get one of the Panasonic microwaves with their "Inverter" feature. It really does run the magnetron at different power levels. It works quite nicely.
  - hackuser 11y ago
    > Panasonic microwaves with their "Inverter" feature Some GEs claim to use inverters but only for defrosting. I've been wondering why they wouldn't use it for other functions.
- bazzargh 11y ago
  Solid-state microwave generators have been developed to replace magnetrons recently, and they can run at variable power. http://electronicdesign.com/blog/say-good-bye-last-vacuum-tube-product http://electronicdesign.com/blog/say-good-bye-last-vacuum-tu... Using the MHT1003N, manufacturers can use from one to eight of these 250 W units to build a microwave oven with the desired power level. And the magnetron’s 4 kV power supply goes away in place of a supply of 28 to 50 volts. Furthermore, the crude on-off control of the magnetron can be replaced with full variable power control. However, as far as I know there's no consumer devices containing things like this yet - the only ones I've seen were concept devices from Freescale. This article suggests we won't see them until 2017, and then only in high-end cookers: http://www.electronicsweekly.com/news/design/the-future-of-microwave-cooking-is-solid-state-2016-01/ http://www.electronicsweekly.com/news/design/the-future-of-m...

by jahnu 11y ago

Can anyone here explain to me why microwave ovens always have their power settings as multiples of some value, e.g. 200/400/800w but never have the ability to set a specific power output, e.g. 425w.

trymas 11y ago

Microwaves with turning knobs (example [0], maybe not the best, but you'll get the point) can have arbitrary power setting. My personal, electronic microwave, has values 125/250/500/750W so not completely exponential (I guess, that's what you meant?). One thing is, you can always (?) set arbitrary time, so you can compensate to gaps in power settings. Other thing, maybe electronics are more simple with power settings like these? When I see exponential settings I would always think of analogy to photography and 'f-stops' [1]. Some devices have exponential settings due to the physical nature of something, but is it the case with microwaves, I don't know. [0] http://www.firstiraq.com/sites/default/files/products/5002-1_neu.jpg http://www.firstiraq.com/sites/default/files/products/5002-1... [1] https://en.wikipedia.org/wiki/F-number https://en.wikipedia.org/wiki/F-number

jahnu 11y ago
Yeah I was wondering if it was analogous to transformers where you have multiple coils all wound together and you combine them in various ways to get different voltages. I have almost no idea how a magnetron actually works.

rainforest 11y ago

At a total guess it's down to the lack of precision in the output at anything other than full power. Most (all?) microwaves just pulse the magnetron to achieve an average delivery of the rated power so the difference between 400W and 425W would be dependent on the time the microwave runs, given most tend to use a fairly long time period. You can see this effect if you run a microwave on low power for a short period - sometimes the magnetron will be running for the full duration.

skykooler 11y ago

Microwave ovens use magnetrons to produce the microwave radiation. Magnetrons cannot be run at anything less than full power. Some microwaves have additional coils in the magnetron that can be connected to increase the power level, but it's limited to the power levels you can get from the various combinations of coils. For the same reason, running a normal microwave at "50% power" actually means it runs at full power for several seconds, then switches off for several seconds, then repeats. The pulses are so long because starting and stopping are hard on the magnetron.

Grishnakh 11y ago
This isn't true, if you get one of the Panasonic microwaves with their "Inverter" feature. It really does run the magnetron at different power levels. It works quite nicely.
- hackuser 11y ago
  > Panasonic microwaves with their "Inverter" feature Some GEs claim to use inverters but only for defrosting. I've been wondering why they wouldn't use it for other functions.
bazzargh 11y ago
Solid-state microwave generators have been developed to replace magnetrons recently, and they can run at variable power. http://electronicdesign.com/blog/say-good-bye-last-vacuum-tube-product http://electronicdesign.com/blog/say-good-bye-last-vacuum-tu... Using the MHT1003N, manufacturers can use from one to eight of these 250 W units to build a microwave oven with the desired power level. And the magnetron’s 4 kV power supply goes away in place of a supply of 28 to 50 volts. Furthermore, the crude on-off control of the magnetron can be replaced with full variable power control. However, as far as I know there's no consumer devices containing things like this yet - the only ones I've seen were concept devices from Freescale. This article suggests we won't see them until 2017, and then only in high-end cookers: http://www.electronicsweekly.com/news/design/the-future-of-microwave-cooking-is-solid-state-2016-01/ http://www.electronicsweekly.com/news/design/the-future-of-m...