High Voltage DC-DC Converter

[ZincBear]

magnetron input voltage

Hi all,

i am trying to power up a magnetron with a battery. However, a magnetron requires a high DC input power of >1kW and a high input voltage of >1kV. Is there a DC-DC converter/transformer that is capable of such a conversion?

 

[FvM]

can you induce dc voltage with dc voltage

Actually, a current source capable of delivering 3.5 - 4 kV is required, in a addition a heater supply at the high voltage level. No problem in general, if your battery can handle the power.

Byt the way, you can operate a magnetron at any power level up to nominal power, with less RF output of course.

 

[ZincBear]

simple high voltage dc-dc converter schematic

So in this case, am i right to say that the battery is the current source?

Based on current standards, standard batteries come with 12VDC. Is there a transformer that can convert the standard battery voltage of 12V to say, 1kV?....A search on the net hardly gives any results....

Yes, after reading some materials, it seems like a magnetron can operate at different power levels, depending on the input DC power. But what actually determines the minimum input power? Is it the filament voltage & current, or the anode voltage & current?

 

[Audioguru]

high voltage dc/dc converter

A battery is DC. A transformer uses AC.

You need the battery to drive a high current oscillator that feeds AC to the stepup transformer then you need to use a high voltage rectifier and filter capacitor to get high voltage DC for the magnetron.

 

[umery2k75]

microwave magnetron input voltage

I know magnetron of Microwave oven, my oven is of 700W and I have UPS of 1875VA or 1500W. I have 2 batteries of 145AH, so 290AH altogether. This means I can drive my microwave oven right from my batteries.

a magnetron requires a high DC input power of >1kW and a high input voltage of >1kV

What I know is that microwave oven runs from 220VAC and mine consumes 700W. So I can use battery source to power up microwave oven(with magnetron inside) from 220VAC using UPS or inverter.

 

[ZincBear]

do lead acid batteries induce dc current

Thank you for the inputs!

Seems like i should use a DC-AC inverter to convert the 12VDC from battery(Ratings: 12VDC, 30mAH) to 230AC. I suppose a typical inverter suitable for this application is found here:
https://www.dcacpowerinverters.com/itemdesc.asp?ic=PW1100-12

This inverter can give me a continuous output AC power of 1100 W, which should be sufficient to drive an 800W-1kW magnetron.

Are all the pieces to the jigsaw in place?... Experts, what do u think?

I did consider using DC-DC converters. This will result in a direct connection between the battery and the magnetron. However, i am unable to find such high power and high voltage converters....any idea? Or is the inverter idea better?

 

[Eugen_E]

microwave oven voltage doubler

12VDC, 30mAH?

A mistake? :idea:

 

[Mr.Cool]

operate a magnetron

http://www2.iee.or.jp/ver2/honbu/14-magazine/log/2006/2006_02d_16.pdf

 

[FvM]

dc to dc converter type 597

This inverter can give me a continuous output AC power of 1100 W, which should be sufficient to drive an 800W-1kW magnetron.

A magnetron has about 70% efficiency, so you need 1.15 kW DC input for 800 W RF output, additionally 30 to 40 W filament supply.

You didn't tell, if you need nominal (high) output power or intend a low power microwave application. Standard (home appliance) magnetrons can be operated at low power(e. g. a few 10 W), but the achieved stability depends on the cavity design and power supply output impedance.

 

[ZincBear]

dc to dc voltage boosters

12VDC, 30mAH?

A mistake? :idea:

Sorry, its a mistake. It should be 30 AH.

I am assuming that i am operating this magnetron for only 15mins. Hence, the battery can output 30X4=120A for 15mins. Multiply that with 12VDC, and Pout=1.44 kW. Am i right?

Added after 3 minutes:

This inverter can give me a continuous output AC power of 1100 W, which should be sufficient to drive an 800W-1kW magnetron.

A magnetron has about 70% efficiency, so you need 1.15 kW DC input for 800 W RF output, additionally 30 to 40 W filament supply.

You didn't tell, if you need nominal (high) output power or intend a low power microwave application. Standard (home appliance) magnetrons can be operated at low power(e. g. a few 10 W), but the achieved stability depends on the cavity design and power supply output impedance.

You got me curious there. Do you mean i can reduce the amount of DC voltage and current into the magnetron, which will in turn reduce the output power of the magnetron?


My original plan is to use it as high power microwave source, launching it into a matching waveguide launcher. I hope the 12VDC/30AH battery is sufficient!

 

[FvM]

converter dc-dc 1000v

If you want high power output, you can't reduce the supplied power to the magnetron of course. This point wasn't obvious from your previous posts.

You should be aware, that the 0.25 h capacity of a lead-acid battery is considerably lower than the nominal 30 Ah, that is specified for a 20 h discharge period usually.

 

[ZincBear]

microwave oven magnetron voltage transformer

Point noted.

However, i am still unsure if a DC-AC inverter is needed. Can i simply connect the battery direct to the magnetron, bypassing the AC circuitry?

 

[umery2k75]

dc dc converter pdf power ups high voltage

Forget all about DC-AC,AC-DC,DC-DC,AC-AC
1)To drive magnetron, typically you need around 1000-2000V. How are you gonna get this from 12V battery?

So, its time for boosting 12V to around 2000V. Okay, transformer are known to UP and DOWN voltage levels, that's sound really good, it seems like you are gonna get a Step Up transformer with the battery and your problem seems to be getting solved. If you go ahead with that by connecting the 12V battery with the Step up transformer, you just won't get Step Up voltage on secondary of transformer,because DC will induce a constant flux in the transformer core, consequently in the secondary coil. So constant flux cannot induce a current in the secondary.So no step up voltage.
You

2)You need to use DC-DC booster circuits, now once you get a constant DC source of 2KV, now can you use it to power up your magnetron now?

In microwave ovens 2KV voltage is applied in 50/60Hz, that is a pulsed DC voltage and not a constant DC voltage.In conventional microwaves oven, what happens is that they first used transformer that steps up the voltage, then they used voltage-doubler circuit, then they apply on the magnetron, remember if you see 800W or 1000W microwave oven, that's actually is the wattage of pulsed DC voltage that is applied on magentron.

I think continous DC source of 2KV should work on magnetron, but that will dramastically increase the wattage consumption.

It seems like you need to focus on two things
A) DC-DC converter topology and it's circuit
B) How to apply constant DC source to magnetron

You could also make some kind of circuit, that will actually give DC pulsed as output of 2KV from DC-DC.Make a circuit that takes constant DC 12V as input and output 2KV pulsed DC output @50/60Hz.

Added after 7 minutes:

What kind of battery rating is that? My friend was asking for a smaller UPS circuit diagram which he wants to make, I asked him what kind of batteries rating you are going to used. He said 12V 28W, I have plenty of them. I said him you must be wrong, batteries are usually in V/AH and not in W. He said no I'm correct about this, he than put his battery on the scanner and send the picture to me, and told me ,you don't seemed to be believing in me.
We were having this discussion, so I thought, how about if I share it in this.Usually battery is rated in V/AH.

 

[FvM]

dc to hv dc converter

I like to correct some errors in the previos post.

1. No usual home appliance magnetron runs from 1 or 2 kV DC voltage, a typical anode voltage is around 4 kV.

2. Although they are often operated with 50/60 half-wave rectified AC respectively pulsed DC, they work with clean DC as well. There's no significant difference in efficiency. You can get power supplies for industrial microwave applications, that use inverters and have a DC output, see **broken link removed**. I've used a CM340 in an analytical instrument.

The usual specification for magnetrons is average RF output. Average DC input is heigher by a factor of about 1.4 as said, pulsed input and output is a multiple of these values in case of a pulsed supply.

3. Apart from the problem of battery current delivery and capacity, it would be possible to build a 12V DC operated inverter (better 24 or 48 V, I think) as well.

See a typical magnetron datasheet for reference.

 

[Mr.Cool]

220v ac dc inverter 1kw pdf

battery in W?

if that is not a type-o then there is only one explanation.

the battery can NOT source reactive current, i.e. its ripple current rating is 0. it can only source watts, acdtive power, or DC current (all same thing). fuel cells are like this, which is why you need supercaps on output of your fuel cell if your load is going to produce ripple currents.

Mr.Cool

 

[FvM]

high voltage dc converter

if that is not a type-o then there is only one explanation

I don't think it's a typo, but it probably doesn't mean too much, you're rather overstressing this specification. I guess, it's a usual lead-acid battery with usual properties. The specification may be meaningful related to UL certification of the product or another particular safety regulation.