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Author Topic: Microwave capacitor question.  (Read 13360 times)

magnetman12003

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Microwave capacitor question.
« on: February 03, 2016, 02:09:16 AM »
I have a metal cased hi voltage Microwave capacitor. Its rated at 2100 volts AC.  .90 uf.

Is this capacitor a electrolytic capacitor where polarity has to be observed before its connected into a
circuit?  Or it does not make any difference which is the positive or negative side?

There are no polarity markings on the metal case at all?

Anyone familiar with this type of capacitor?
 

sm0ky2

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Re: Microwave capacitor question.
« Reply #1 on: February 03, 2016, 02:29:51 AM »
it doesn't matter which way you charge it,
in normal operation the plates switch back and forth at high frequency
to power the magnetron

citfta

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Re: Microwave capacitor question.
« Reply #2 on: February 03, 2016, 02:32:12 AM »
A  capacitor that is marked AC has no polarity.

Carroll

bmind23

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Re: Microwave capacitor question.
« Reply #3 on: February 03, 2016, 07:05:44 AM »
Can I use this capacitor as DC and charge by DC current?

leo48

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Re: Microwave capacitor question.
« Reply #4 on: February 03, 2016, 02:25:37 PM »
Quote
Can I use this capacitor as DC and charge by DC current?

 Yes, but this capacitor has a small capacity 0.90 Uf

Leo48

sm0ky2

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Re: Microwave capacitor question.
« Reply #5 on: February 03, 2016, 04:26:54 PM »
Yes, but this capacitor has a small capacity 0.90 Uf

Leo48

"microwaves" have a very tiny wavelength, the one used for this capacitor has the wavelength of 12cm
When you compare this to the diameter of the water molecule, (0.275nm)
 you can see this hits on a multiple of the 6 & 1/6th resonant node.

The excitation frequency of the water molecule, that we use for cooking food, is (approx.) 2.45 Ghz (2,450 Mhz)

this means that the capacitor is charging and discharging at a rate of 2,450 million times per second.
when you flip the DC switch on this cap, it will reach maximum capacity before the rest of your circuit even finishes turning "on".... the large plate size allows for a high voltage to be stored, but there is very little "quantity" stored inside.

you can consider the "farad rating" to be like the size of a swimming pool.
Say the pool has 1,000 Gallons in it.
 If "current" was the amount of water flowing out, you could drain the pool at 10 gallons per second for 100 secs.
Or you could drain the pool at 100 gallons per second for 10 secs.
etc.
So, using this capacitor, theres only a tiny bit of "current" you can pull from it, at whatever voltage you charge it to.

solution? add more caps in parallel.




leo48

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Re: Microwave capacitor question.
« Reply #6 on: February 03, 2016, 05:24:37 PM »
 8)
No no the capacitor present in microwave ovens A blend is used to straighten the HT diode
 and doubling the voltage of 2100V AC adapter to power the magnetron at 4200V dc
negative, and 3.5V 10A per filament ignition.

Leo48

Paul-R

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Re: Microwave capacitor question.
« Reply #7 on: February 03, 2016, 06:34:22 PM »
Bear in mind that it probably has a 1megohm resistor connected across the terminals, situated just under the top casing.

It might be possible to drill it out by drilling a few mm into the unit between the terminals. (Connect a multimeter across the terminals until the value drops to nil). Also, the unit may be full of oil and so, it may be a messy process.

If you have a few of them, maybe from your local recycling centre, you could chop up one to see what's going on. They look well made.

massive

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Re: Microwave capacitor question.
« Reply #8 on: February 03, 2016, 07:15:12 PM »

shake the cap , you will hear the oil inside . all the info is written on the cap . it charges and discharges at the supply frequency , either 50hz or 60hz .
MW oven uses a Villard circuit

sm0ky2

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Re: Microwave capacitor question.
« Reply #9 on: February 04, 2016, 07:28:37 AM »
8)
No no the capacitor present in microwave ovens A blend is used to straighten the HT diode
 and doubling the voltage of 2100V AC adapter to power the magnetron at 4200V dc
negative, and 3.5V 10A per filament ignition.

Leo48

so the 2.45 Ghz is actually a magnetic response??
I never looked at the circuit boards in these things, I usually just throw them away when I strip the magnets out....

I always assumed they were doing it with IC chips or transistors and then sending 2.45 Ghz through the magnetron....

leo48

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Re: Microwave capacitor question.
« Reply #10 on: February 04, 2016, 09:22:07 AM »
Quote
so the 2.45 Ghz is actually a magnetic response??
I never looked at the circuit boards in these things, I usually just throw them away when I strip the magnets out....

http://hyperphysics.phy-astr.gsu.edu/hbase/waves/magnetron.html


Leo48

sm0ky2

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Re: Microwave capacitor question.
« Reply #11 on: February 04, 2016, 04:41:35 PM »
http://hyperphysics.phy-astr.gsu.edu/hbase/waves/magnetron.html


Leo48

that's amazing, its simply a factor of the size of the holes in the plate behind the emitter......

Thanks for this info!!!

magnetman12003

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Re: Microwave capacitor question.
« Reply #12 on: February 04, 2016, 09:44:41 PM »
I have a metal cased hi voltage Microwave capacitor. Its rated at 2100 volts AC.  .90 uf.

Is this capacitor a electrolytic capacitor where polarity has to be observed before its connected into a
circuit?  Or it does not make any difference which is the positive or negative side?

There are no polarity markings on the metal case at all?

Anyone familiar with this type of capacitor?

Can I use three 450 volt caps in series to allow me to work with 1350 volts??   I have two 330 mfd caps
Presently and by adding a third cap all in series should I be able to work with higher voltage and less capacitor value??   Three 330 mfd caps in series is ???? Mfd.      After reviewing the input from all I see the microwave cap won't work for me.

massive

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Re: Microwave capacitor question.
« Reply #13 on: February 05, 2016, 02:38:12 AM »
google series capacitance and youll find the reciprocal formula