Control Magnetron Power Using a Variac and 2 MOTs

If you are connecting the secondary to the cathode, what is your reference? your question will answer itself.

Schematics, please.

The magnetron is probably designed for the optimum output. If you want to vary the output level, you might consider controlling it by introducing an absorber.

..." a magnetron designed for an output power of 200 kw peak will operate quite well

at 100 kw peak output by simply reducing the modulator drive level."

http://www.cpii.com/docs/related/2/Mag%20tech%20art.pdf

http://www.microwavejournal.com/articles/2090-a-solid-state-power-supply-modulator-system

http://www.apexanalog.com/wp-content/uploads/2012/08/PwmBasics.pdf
http://en.wikipedia.org/wiki/Pulse-width_modulation

http://en.wikipedia.org/wiki/Microwave_burn

http://educypedia.karadimov.info/education/microwaveoven.htm

As I posted #2, the info you have shown indicates a full voltage drive and PWM to control net current through the device.

Same as PWM for slot cars and model trains, among other applications.

I service kitchen equipment and the only thing I care to know about microwaves is that...if you don't know what you are doing 100%... they WILL kill you....sooner or later.......probably sooner..... I am curious as to why you want to do this..Application ??

Thank you for sharing your expert knowledge, Dammit!!! This idiot doesn't realize that there's around 5kV lurking in that circuitry, energized or not, that the magnetron output may not be continuously variable from 0-100% because the magnetron does not "fire" below a certain plate voltage, that the positive side of the high voltage supply is connected to chassis ground not the other way around, that microwaves leak out any time the unit is operated without all the covers and screws in place, etc., etc.

I gotta ask...how many people have you seen killed by microwaves...in your line of work??? I could see if you got your head in there, but getting the door closed would probably break your neck anyway.

Any object dropped from a height can be lethal, Bwana.

Why do you usually end with a derogatory pseudoname? I find it quite offensive!

Are you a member of the EOGOP?

Door closed...... Cute....... YOU need to open the back end and play around... I don't know anyone that was killed...only a friend of a friend...... it was a bench test and it killed him...I don't service them because I am not qualified...... you are qualified so you can put your fingers in there and poke around... Original poster is very qualified considering his/her posts.... How about you.........

When I wporked in the ship yard on the great lakes, there was a technician that worked on the ships radar unit in one of the yards on the east coast......... never locked it out.... then they ran tests on the radar unit.......... I'm not going to go on about the condition of the corpse.

Can you tell us what color the wires are?

That will help in our analysis to determine which spell we use.

ffrohit3

Voodoo Power spells.

Be aware that one of the secondary wires is connected directly to the Iron corner of the coil. .

Thanks everyone for all the very helpful comments. Yes, I know that there's a 4-5 kV flowing around the circuit and about the Hartee voltage. Thank you for your concern about safety! I actually want to use this for a short project on moisture measurement of some very large pieces of materials. A microwave brick oscillator (generating some few hundred mW's) can't generate enough power go through the material, so a much higher MW power is needed. I have successfully connected a magnetron to a pyramidal horn antenna and measured the emitted power collected on another horn antenna about 0.8 meter away (with me and the measuring equipment hiding behind a metallic screen at a distance from the horn antenna with a MW oven leakage detector in my hand that is on all the time). The only problem is that the emitted power is so high that it is well over the range of my power detector, even with the attenuator in place. So I am looking for a way to significantly reduce the emitted power. If the direct variac-to-MOT method won't work (magnetron starts to fire at a too high power already), I think I'll go for the duty cycle method instead, together with the variac setting to get the magnetron to fire at the lowest possible power. Thanks everyone again for all the very helpful comments and for all the concerns for safety! :)

Why didn't you state your goal in your original post and save us a lot of guesswork. You would have found out that there are already products out there that do what you want without reinventing the wheel.

I guess that you're doing this on the cheap, but you're facing a multitude of problems that have already been solved; the main ones being calibration, accuracy, repeatability, and precision. Just because you know how much energy gets absorbed by your moisture laden material tells you nothing about how much was reflected off it, how much was absorbed by the material, moisture, and ambient.

See if you can buy one of these on the used instrument market:

http://www.hydronix.com/

http://www.grecon.com/en/moisture-analysers-mm-6000

http://www.rgi-ms.com/html/moisture_principles.html

https://www.berthold.com/en/pc/moisture-microwave-technology

Why microwave?

What material and what moisture content are you measuring?

It would be much cheaper and simpler to use Infrared and Near infrared to detect moisture content.

You could also differentate between the measured object and steam in between the object and the measuring device this way.

And the souce could be a simple incandescent bulb driven at a lower-than spec voltage.

I saw one working on this principle about 30 years ago.It was very accurate and reliable.

The IR was used for actual moisture,and the NIR was used for vapor detection.

Damn...I just gave an A. P. a good answer. I am slipping. Would somebody please (besides me) invite this guy to the forum....I am impressed enough to do so.

In addition to the infrared types I mentioned,there are conductivity types for use in certain applications, such as web (paper,textiles,etc.) and batch applications(Grain silos,etc.).

This technology has proven accurate and relaible for over 50 years,and is still used widely.

One such company is Strandberg Engineering (with which I have no affiliation or interest) but I have worked with their products.

They even make a hand held unit for spot checking material while in process and in motion.

Don't limit yourself to one technology.

Now if we can just Modify this to Burn out Po-Po's Radar guns, I'd be happy!