Hi, to make it short:
For a project I need a high voltage, high power, high frequency voltage source. I thought about:

Mains voltage (230 V, 50 Hz) -> Rectifier (output=325 VDC) -> H Bridge with 4x IRFP460N (driven by arduino and IR2110) -> H Bridge AC to MOT -> MOT output: approx. 2 kV at high frequency (idk like 1 or 2 kHz) -> my other project

Due to my low experience in this field I ask you if my plan is going to work. Especially if those transformers can work at those high frequencies.

Please no safety tips. I know how to deal with these dangers, only functional comments pls. THX

 

Microwave transformers are designed for 50Hz so they will only allow a limited increase in frequency without excess loss and consequent heating.

edit: or 60Hz, if microwave volume is in cu. in.

 

Certainly the iron in a MWO transformer is NOT selected for high frequency operation. so the effective inductance will be quite a bit and the losses will not be small. Then consider the size of the transformer core in a similar rated switch-mode power supply. I would not bet much on it working. BUT if you ran it as an inverter at just a couple hundred HZ it might work out well. Just replace the magnetron heater winding with the feedback winding, and be sure to remove those magnetic shunts.

 

Any transformer designed for mains operation frequencies, will overheat and have poor efficiency at high frequency operation due to eddy current, hysteresis, and other parasitic losses.

 

For quite a few years mains step down transformers were used as step up transformers to operate mobile radio transmitters. SO they can work, even though not as efficiently, running at a few hundred hertz. NOT Kilohertz.

 

A proper schematic would do.

 

Even with high-grade magnetic steel, which a MOT definitely doesn’t use, the maximum frequency would be 400 Hz.
Higher frequency than that, and the steel core would become extremely hot, unless operated at a quite low flux density.

 

Maybe the innards of an inverter-based microwave might be a better starting point. I have no idea, but don't those use a high frequency off-line inverter to generate the magnetron power???

 

Maybe the innards of an inverter-based microwave might be a better starting point. I have no idea, but don't those use a high frequency off-line inverter to generate the magnetron power???

Certainly they do use a fairly high frequency inverter. I rescued the inverter module from an inverter powered microwave and based on the core it runs well into the kilohertz range. But I have not dug into it yet because it is obviously not built to be serviced, only to be replaced. What is interesting is that I do not see much filtering on the rectified mains side of the inverter. It does look a bit like the high voltage side uses a voltage doubler scheme, so the ac output might not be as high as you want.

 

For quite a few years mains step down transformers were used as step up transformers to operate mobile radio transmitters. SO they can work, even though not as efficiently, running at a few hundred hertz. NOT Kilohertz.

Another common application was the old car radio vibrator power supplies, that used the vibrator to convert from 12vdc, to the 100-150 alternating voltage volts required for the valves used in the radios at that time.
The transformer output then fed the usual HV DC and tube (valve) rectifier.
Another style of vibrator was synchronous, in order that the synchronized output of the transformer resulted in DC without any rectifier, tube etc, being used.
They had a large audible "Buzz" , so freq was quite low.