current limiting

To: tesla-at-poodle.pupman-dot-com
Subject: current limiting
From: Tesla List <tesla-at-stic-dot-net>
Date: Sat, 12 Apr 1997 23:41:13 -0500
Approved: tesla-at-stic-dot-net
Subject: 
        current limiting
  Date: 
        Sat, 12 Apr 1997 15:07:50 -0700
  From: 
        Gary Weaver <gweaver-at-earthlink-dot-net>
    To: 
        tesla-at-pupman-dot-com


I did some more current limiting tests using 2 different transformers in
series with my 16,800 watt high voltage transformer.
The high voltage transformer primary is 240 volts and the secondary is
18K.  Both current limiting transformers are industrial
control circuit transformers that I picked up at the scrap yard for 15
cents a lb.

500 watt transformer,  Primary 240 volts,  Secondary 120 volts.  Wt 10
lbs.  The transformer primary winding is connected in
series with the 16,800 watt high voltage transformer primary winding. 
Resistors are connected across the secondary winding
to limit the current threw the primary winding.  I am using a house type
ON/OFF light switch in series with each resistor.  The
current threw the transformer can be changed by turning ON and OFF the
resistors.  It does not over heat at 2516 watts, this
is about 5 times the transformer rating.  At 3000 watts it gets warm
after about 5 minutes.  It over heats very fast at maximum
power 3600 watts and would probably burn up after 60 seconds of use
while 30 seconds makes it very hot. 

Resistance in ohms      Primary Current in Amps       Watts
      0                                  
32.72                           3600
      4                                  
12.5                             3020
      5                                  
10.5                             2516
      6                                    
8.4                             2013
      9                                    
6.3                             1510
     12                                   
4.2                             1007
     25                                   
2.0                              484
   no resistor                           
.2                                48


3000 watt transformer,  Primary 240 volts,  Secondary 240 volts.  Wt 55
lbs.  The transformer primary winding is connected
in series with the 16,800 watt high voltage transformer primary winding.
Resistors are connected across the secondary winding
to limit the current threw the primary winding. I am using a house type
ON/OFF light switch in series with each resistor.  The
current threw the transformer can be changed by turning ON and OFF the
resistors.  It does not over heat at 12000 watts.  I
could not test it above 50 amps because I have a 50 amp breaker in my
shop.

Resistance in ohms      Primary Current in Amps         Watts

     4                                       
50                             12000
     6                                       
34                               8160
     8                                       
28                               6720
   10                                       
22                               5280
   12                                       
18                               4320
   16                                       
14                               3360
   22                                       
11                               2640
   24                                       
10                               2400
   25                                        
9.5                             2280
  no resistor                             
1.2                               288


Both transformer seem to do just fine at several time there power
rating.  


Gary Weaver          Experement # 7924