[Amps] PS Theory ?

[Ron]

Hmmm .

Let's see ......the question was " How can I tell the power capability of a transformer?".



I have seen in the literature or handbook where one could resistively load
the transformer so that the unloaded voltage  would drop by 10%.  The loaded voltage and current would be the rated voltage and current for that paticular transformer.


In doubler service , you wouldn't expect the same supply output current but 1/2 if you could draw smooth current.
I think that this was what the fellow was asking by using that example and was a little confused.  I don't think that all peak numbers add anything to the answer to the question.

As far as peak instant currents and service ....well that another issue.


Your not going to drive the core into saturation as the primarys are running
fixed rated voltage so the only worry is IR heating in the windings.  Drawing
4x currents into a capacitive load is acceptable in that the heating is also
short and the windings and core will shed the heat during non conduction times.

If you have such a large filter where you are running conduction times of
1 mS out of 8 mS, you might want to consider adding a series inductance before the diodes or filter to lower harmonic currents and correct the power factor instead of re designing the transformer you have at hand. 

Last rule of thumb.   
If you can fry an egg on it ...it's too hot :-o

---
Ron









rlm wrote:

>  
>
>>Actually in doubler service I think the transformer peak current
>>is about four times the DC output current in a capacitor input filter.
>>    
>>
>
>9x to 10x is closer to it since the conduction period is c. 1mS per 
>half-cycle.
>
>  
>
>>A transformer should be designed for doubler service.
>>
>>    
>>
>Amen,  Mark  
>  
>
>>On Tue, 26 Aug 2003 11:38:31 -0400 Ron <w8ron at stratos.net> writes:
>>    
>>
>>>When you feed it to a doubler , the current is not .5 A but .25A.
>>>
>>>THe remainder may be due to CCS and ICAS duty.
>>>---
>>>Ron
>>>
>>>
>>>Mike, K8LH wrote:
>>>
>>>      
>>>
>>>>Please excuse the dumb question...  I'm trying to figure out how to
>>>>determine the power handling capability of transformers (I did take 
>>>>        
>>>>
>>>a
>>>      
>>>
>>>>quick look through the ARRL Handbook last night)...
>>>>
>>>>Questions: 
>>>>
>>>>How can you determine the power handling capability of a 
>>>>        
>>>>
>>>transformer???
>>>      
>>>
>>>>For example, the secondary on the transformer in my Heath SB-201 is
>>>>rated at 800 VAC at 0.5 amps...  I would think this transformer 
>>>>        
>>>>
>>>would
>>>      
>>>
>>>>only be good for about 400 watts of power (800 x 0.5) but it seems 
>>>>        
>>>>
>>>that
>>>      
>>>
>>>>if you feed this secondary into a full-wave bridge rectifier and
>>>>capacitors you would get about 1,000 volts and 0.5 amps under load 
>>>>        
>>>>
>>>(500
>>>      
>>>
>>>>watts), or feed it into a voltage doubler circuit, like that in the
>>>>SB-201, and you get about 2,000 vdc at 0.5 amps under load (1,000
>>>>watts)...
>>>>
>>>>I'm confused...  What am I missing???  Thanks...
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>>>>
>>>>
>>>> 
>>>>
>>>>        
>>>>
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>>>      
>>>
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