[Amps] Re: Step-start calculation

[jeff millar]

Rich...

Thanks for the numbers, its educational. The program assumes mains 
resistance of zero.  Since you know the value, it adds to primary 
winding resistance.

Results at 240V in, 2.2M RL, parallel 2 x 93 uFd= 186 uFD
    Vout = 4435V
    Ipk turnon = 70A

Loading the output (knowing what you like to run)
    RL = 2K   Vout = 4050 to 3985V (65V ripple)
    RL=1.5K  Vout = 3960 to 3878V (82V ripple)
That's a nice supply. 

The main resistance significantly limits inrush, setting it to zero 
produces...
   Vout  =  4440 noload, , 4190V at 2K
    Ipk turnon = 108 Amps

jeff, wa1hco

R. Measures wrote:

> Jeff ---- Here are the needed parameters:  C is two, 93uF in a FWD.  
> The mains R is 0.127-ohms, xfmr primary winding R = 0.059-ohms.  The 
> transformer sec. potential is 3200V-rms, Rsec = 16.5-ohms.  The load 
> at switch-on is 2.2M-ohms (the 22, 100k equalizer resistors).
>
> I do not see how this computer app. could calculate inrush-I without 
> knowing the mains ESR?
>
> On Nov 20, 2004, at 9:04 AM, jeff millar wrote:
>
>> PSU designer (http://www.duncanamps.com/psud2/download.html) can do 
>> this calculation and I've got it running here.  The model needs some 
>> values for various parameters.  Here's some results for some sample 
>> HVPS with zero voltage switched
>>
>> Case 1:
>>    Transformer
>>       1500V secondary, 10 Ohms
>>        240V primary, 0.1 Ohms
>>    Full wave doubler
>>       40 uF caps (2)
>>    Results
>>       4K load impedance
>>       Output ripples from about 3900 to 3700 (~5%)
>>       Peak current at turn on 27 Amps
>>       Peak current on each line cycle 9 Amps
>>
>> Case 2:
>>    Transformer
>>       2600V seconday, 10 Ohms
>>       240V primary, 0.1 Ohms
>>    Full Wave Bridge
>>    40 uF cap
>>    Results
>>       4K load resistance
>>       Output ripples from about 3500 to 3300 (
>>       Peak current at turn on 42 Amps
>>       Peak current on each line cycle 6 Amps
>>  Adjusting parameters and generally looking at result shows
>>    Magnitude of turn on current surge mostly depends on capacitance
>>    Transformer resistance has little effect (surprise!, change values 
>> about 20%)
>>    Peak current at turn on of 5-10 times cycle to cycle peak with 
>> enough capacitance to limit ripple to 5%
>>
>> Conclusion...
>>    Zero voltage turn on works
>>    Keep the capacitance low (good idea anyway to limit flash over damage
>>
>> If anyone wants to run the model with different values just send me 
>> an email.  Or if you get some interesting results, please post them.
>>
>> jeff, wa1hco
>
>  
>