[Amps] Microwave Oven Power Transformer

[TexasRF at aol.com]

Hi All, another technique is using a resistor in series with the primary to 
 drop the voltage enough to prevent the transformer heating during standby. 
A  relay would be required to short the resistor during transmit periods.
 
The resulting standby plate voltage would be in the ballpark of the operate 
 plate voltage. This would eliminate a surge in the primary circuit when  
switching to transmit.
 
It also seems plausible to use the primary turn on surge limiter for this.  
The relay normally used to short the limiter resistor would be energized by 
the  ptt circuit. 
 
I have used the technique to keep twt voltages from soaring during standby  
and it works quite well.
 
73,
Gerald K5GW
 
 
 
 
 
In a message dated 11/18/2012 7:52:52 A.M. Central Standard Time,  
gzook at yahoo.com writes:

Would it  not be possible to use a relay in the primary to disconnect the 
transformer  during standby?  Of course, the contacts on the relay would have 
to be  able to "handle" the current.  This should keep down the heating  
factor.

Glen, K9STH


Website:   http://k9sth.com


________________________________
From: Angel  Vilaseca <avilaseca at bluewin.ch>
To: amps at contesting.com 
Sent:  Thursday, November 15, 2012 11:16 PM
Subject: Re: [Amps] Microwave Oven  Power Transformer

For cost reasons, Microwave oven xformers are  optimized specifically for 
their use in a microwave oven.
They are OK  as long as they supply their nominal power to a load.

In the standby  mode, they get *very*  hot.
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