Why this type of fans

Tonyr1084

Joined Sep 24, 2015
5,063
to circulate the microwaves,
No. There may be in some models a slow rotating gear reduction motor that turns a deflector (aluminum most likely) to redirect the microwaves in the oven chamber. There's also a turntable motor to rotate the food. The intention is to distribute the energy as evenly as possible. The fan is for cooling the transformer and magnetron. Other components may be inadvertently cooled by moving air as well. But the hottest parts are the transformer and the magnetron.
 

andrewmm

Joined Feb 25, 2011
574
No. There may be in some models a slow rotating gear reduction motor that turns a deflector (aluminum most likely) to redirect the microwaves in the oven chamber. There's also a turntable motor to rotate the food. The intention is to distribute the energy as evenly as possible. The fan is for cooling the transformer and magnetron. Other components may be inadvertently cooled by moving air as well. But the hottest parts are the transformer and the magnetron.

@Tonyr1084

Just as a reference, why do you say its not for rotating the microwaves,
my oven certainly has a plastic "fan" to stir the microwaves, and no table, and a metal fan to cool the magnetron,
 

Delta prime

Joined Nov 15, 2019
496
my oven certainly has a plastic "fan" to stir the microwaves
Hello there
:)I think there is a bit of confusion concerning microwave propagation.
Using something called a “waveguide,” the magnetron sends these radio waves into the compartment. The food that is put into the microwave on the spinning plate is “cooked” evenly by the radiation bouncing around inside. These bouncing waves, when they hit the food, are absorbed and water contained in the food vibrates violently and that is what cooks the food it vibrates at microwave frequencies no fan is needed to disperse the microwave:).
 

AlbertHall

Joined Jun 4, 2014
10,393
Hello there
:)I think there is a bit of confusion concerning microwave propagation.
Using something called a “waveguide,” the magnetron sends these radio waves into the compartment. The food that is put into the microwave on the spinning plate is “cooked” evenly by the radiation bouncing around inside. These bouncing waves, when they hit the food, are absorbed and water contained in the food vibrates violently and that is what cooks the food it vibrates at microwave frequencies no fan is needed to disperse the microwave:).
You need to do this experiment: http://www.planet-science.com/categories/over-11s/physics-is-fun!/2012/01/measure-the-speed-of-light-using-chocolate.aspx

Because the RF is in the form of a standing wave microwave ovens need to either rotate the food on a turntable, or rotate the microwaves with some form of stirrer in the path of the microwaves.
 

Tonyr1084

Joined Sep 24, 2015
5,063
Just as a reference, why do you say its not for rotating the microwaves,
my oven certainly has a plastic "fan" to stir the microwaves, and no table, and a metal fan to cool the magnetron,
If wind could blow microwave radiation or any other form of radio communication then one plane in front of another could not hear the one behind him because his radio signal would be blown back.

The plastic in a microwave oven does not affect the propagation of microwaves. Neither will wind blow the waves around.

Physics.
 

nsaspook

Joined Aug 27, 2009
7,589
If wind could blow microwave radiation or any other form of radio communication then one plane in front of another could not hear the one behind him because his radio signal would be blown back.

The plastic in a microwave oven does not affect the propagation of microwaves. Neither will wind blow the waves around.

Physics.
While I agree that the plastic in a typical microwave oven doesn't provide the stirring function, plastic (some dielectric types like Teflon) does affect microwave propagation. A typical way to convert a linear microwave feed-horn to circular polarization signal reception is to use a insulated plastic insert.
1.JPG
 

andrewmm

Joined Feb 25, 2011
574
I agree this is probably a air fan, but I also had to raise the possibility that is was a microwave stirrer.

For those comments abotu air blowing microwaves, I think they are miss understanding my post.
As is highlighted by others,

Microwaves form standing waves in the oven.

as said by others, this leads to an interference pattern, that leads to concentrated areas of microwave energy and nulls.
The microwave energy , vibrates the water molecules , ( OK any others , but by far away mainly the water )

As is shown above, this leads to well cooked spots and under cooked spots.

The answer is to either move the food through then hot spots, or to move the hot spots through the food.

Most ovens, achieve the former, rotating the food,
but some ovens, such as the one we had,
has no rotating food, but has a rota tor in the wave guide, thus creating a "chaotic" field ,

This stirrer is made of plastic, as the previous poster said, using plastic is very common in microwave engineering to direct the signals. Just about all microwave aerials used on the mobile phone network I have seen have microwave Fresnel lenses on the front to direct the energy , made of plastic.
 

Tonyr1084

Joined Sep 24, 2015
5,063
Clearly the fan in the picture is for stirring air, not microwaves. I have one sitting on top of my cabinet right now. There's nothing special about the plastic blades. That and the fact that when in operation it blew air against the transformer and magnetron.

Out in the garage I have another fan assembly that consists of a squirrel cage fan arrangement directly blowing on the transformer. Haven't a clue what I'll use it for, but it's a nice fan on its own. Plastic blades and plastic shroud. But in the less than one dozen MWO's I've pulled apart I've never seen a fan stirring MW's. Only one had a rotating aluminum blade of odd shapes bouncing MW's about in the oven. It may have been 6 RPM or maybe 10 RPM, I don't recall. But somewhere in the garage are some low RPM motors. Some driven by (I think) 24VAC, and others driven by 110VAC. I've never tinkered with a 220VAC oven. Not likely to find one easily in the US.
 
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