[Amps] MW Oven Transformer question

[TexasRF at aol.com]

Can someone explain what the shunts in these transformers are about? I  can 
see what looks like a stack of four thin strips of metal placed below the  
secondary winding through the two core openings.
 
I assume these make up two shunts. The purpose is not intuitive to me so  
hopefully there is a good explanation about how they work.
 
I have removed the 2100vac secondary winding and replaced it with eight  
turns of thick insulation teflon covered wire to make up a 6.3vac filament  
winding. This winding needs to withstand about 10kv in the twt amplifier it will  be 
used in. With no load connected to the winding it measures 6.84vac so a  
primary resistance will be added to trim the filament voltage. 
 
In checking the primary current, I see 4A flowing with no load. This was a  
surprise and I wonder if this is a result of the shunts?
 
This current is measured with a Radio Shack DVM set to AC amps and may be  
indicating other than RMS current. There is a noticeable spark when the AC is  
disconnected so apparently there is a bit of current flowing.
 
Any info about this is appreciated.
 
73,
Gerald K5GW