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4hv.org :: Forums :: Electromagnetic Radiation
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operate cavity magnetron at low voltages?

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alf
Sat Jun 04 2011, 12:06PM Print
alf Registered Member #3925 Joined: Fri Jun 03 2011, 10:50AM
Location:
Posts: 121
hi,

what would happen if i tried to run a magnetron from a microwave oven at a lower voltage than its supposed to work at?
if i connect the microwave oven to a variac and turn the voltage down, at what point will the magnetron stop working? or will the microwaves always be produced, just less of them proportional to the voltage?

thx. Alf.
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Ash Small
Sat Jun 04 2011, 01:23PM
Ash Small Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
This thread addresses operating magnetrons at reduced power:

Link2

I think it addresses your question directly. It's certainly worth reading and it mentions using a variac.

I think the easiest way to reduce power from a magnetron is to use a smaller capacitor in the doubler circuit though.

It also has some interesting links to other articles on the subject (Doug Coulter can be a bit 'wordy', though).

I'm sure you'll still have other questions after reading it though smile
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Proud Mary
Sun Jun 05 2011, 05:13PM
Proud Mary Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

1307293486 543 FT0 Magnetron Efficiency



1307293501 543 FT0 Magnetron Efficiency 2


Source:

Namba I et al, Low Voltage Magnetron For Microwave Ovens, Journal of Microwave Power, 16 (3 & 4) 1981


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Ash Small
Mon Jun 06 2011, 02:41AM
Ash Small Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
@PM, Any idea what they mean by 'External Conductance' in the above paper?

While this graph relates to the 2M125 and not the more common 2M172, it does indicate that output power is linearly proportional to anode current:


1307328086 3414 FT116954 Output V Current


And anode current can be reduced by using a smaller capacitor in the doubler circuit, as I stated above.

All in all, a very informative paper.
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Proud Mary
Mon Jun 06 2011, 08:33AM
Proud Mary Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Ash Small wrote ...

@PM, Any idea what they mean by 'External Conductance' in the above paper?

Gex is the conductance G of the external waveguide.
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