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Pole Pig Simulation Data 1



Hi All, (view with fixed width font) 

Here is data from Microsim regarding ballasting & PFC cap: 

I checked LTR, RESO, and STR tank cap sizes (10KVA, 14.4kv Pole Pig). 

The voltage angle is set to cross zero at 50.000ms. This is the point of
reference used to check the current waveforms zero-crossing. In some
instances, the current leads the voltage, and in others it lags the
voltage. I used ArcCOS (lead-t/lag-t) for degrees. 

In the last two weeks, I've looked at a lot of waveforms. My purpose here
is to simply look at ballasting and PFC relationships, not actual values.
There is a lot more information with regards to voltage and current due to
waveform phase relationships and where the break is within the waveforms.
But for this, I just wanted to look at the line voltage and current. 

Terry, I read your other post and I agree fully. Keeping it simple is
difficult with this particular testing (that's actually what I'm trying to
do here). The data is interesting and there are relationships here that
appear to follow theory. 

I first ran a test of each cap size using no ballast or PFC in the circuit.
I won't go into current readings, I just wanted to look at the phase prior
to the remaining test. PFC values and ballast values are the same for LTR,
STR, and RESO. I'm not looking for the PFC to use, but simply relationships. 
  

LTR - 250nF (larger than resonant) 
W/no pfc/ballast: R = 0.1 ohms, V-t =50.000ms, I-t=52.572ms, 18.00 degrees 
  
Ballast    PFC    V-time    I-time     Angle 
   (mH)    (uF)      (ms)      (ms) (degrees) 
-------    ----   ------    ------     ----- 
      5      0    50.000    52.854     18.91 << angle increases w/L >> 
     10      0    50.000    53.047     19.51  ** current lagging in all 
     15      0    50.000    53.186     19.93  ** needing PFC 
     20      0    50.000    53.291     20.24 
     30      0    50.000    53.435     20.66 
     50      0    50.000    53.592     21.10 
  
      5    370    50.000    48.950     11.76 << w/PFC, angle decreases w/L >> 
     10    370    50.000    51.255     12.71   ** needs more PFC 
     15    370    50.000    49.104     10.86   ** notice anomoly's with
lead or lag 
     20    370    50.000    51.195     12.40      I tracked this: Due to
poor waveform, 
     30    370    50.000    49.472      8.33 
     50    370    50.000    49.279      9.74 
  
     15    200    50.000    52.031     16.06 - current lagging 
     15    300    50.000    52.059     16.17 - current lagging 
     15    400    50.000    49.964      2.17 <<< Only slight phase shift 
     15    500    50.000    48.044     16.08 - current leading 
     15    600    50.000    47.851     16.86 - current leading 

----------------------------------------------- 

RESO - 128nF (resonant) 
W/no pfc/ballast: R = 0.1 ohms, V-t=50.000ms, I-t=50.883ms,  10.69 degrees 

Ballast    PFC    V-time    I-time    Angle 
   (mH)    (uF)      (ms)      (ms) (degrees) 
-------    ----   ------    ------     ----- 
      5      0    50.000    51.439     13.58 << again, w/L, angle increases >> 
     10      0    50.000    51.871     15.44  ** current lagging in all 
     15      0    50.000    52.194     16.67 
     20      0    50.000    52.436     17.53 
     30      0    50.000    52.769     18.64 
     50      0    50.000    53.136     19.78 

      5    370    50.000    49.726      6.00 << Too much PFC? going up. 
     10    370    50.000    50.574      8.64  ** current lagging here and on 
     15    370    50.000    50.141      4.30 
     20    370    50.000    50.995     11.34 
     30    370    50.000    51.650     14.52 
     50    370    50.000    51.607     14.34 

     15    200    50.000    51.254     12.70 < current lagging 
     15    300    50.000    51.001     11.37 < current lagging 
     15    400    50.000    50.316      6.42 <<< Small phase angle 
     15    500    50.000    50.458      7.73 < current leading 
     15    600    50.000    49.149     10.59 < current leading 
  

------------------------------------------------- 
STR (smaller than resonant) - 64nF 
W/no pfc/ballast: R = 0.1 ohms, V-t=50.000ms, I-t=49.158ms, 10.53 degrees 

Ballast    PFC    V-time    I-time    Angle 
   (mH)    (uF)      (ms)      (ms) (degrees) 
------    -----   ------     ------   ------- 
     5      0     50.000     49.515     7.99 << w/L, angle increases 
    10      0     50.000     49.871     4.12 < leading 
    15      0     50.000     50.219     5.35 < lagging 
    20      0     50.000     50.555     8.50 < lagging 
    30      0     50.000     51.163    12.24 < lagging 
    50      0     50.000     52.024    16.03 < lagging 
  
     5    370     50.000     49.295     9.63 < leading 
    10    370     50.000     49.969     2.02 << slightly leading 
    15    370     50.000     50.573     8.63 < lagging 
    20    370     50.000     51.130    12.07 < lagging 
    30    370     50.000     52.177    16.61 < lagging 
    50    370     50.000     53.549    20.98 < lagging 
  
    15    200     50.000     50.280     6.05 << PFC is not helping? 
    15    300     50.000     50.419     7.39 ** lagging in all 
    15    400     50.000     50.616     8.95 ** I have had strange problems
w/STR's 
    15    500     50.000     50.736     9.77 
    15    600     50.000     50.634     9.08  **I will run these again
(blunder?) 
  

In STR above, the ballast of 10mH with a PFC cap of 370uF looks good, but
in reality, the amount of current may be too much (it's close). STR wave
forms can get really messy, especially with a PFC added. In everything else
I've looked at, using a PFC in an STR set up has identified some problem
(typically - cap voltages become dangerous to the cap if the cap is too
small and the xfmr current is to high). 

LTR's and RESO cap sizes appear to favor PFC use without problems as long
as the PFC value is correct. If the PFC is too small, waveforms get ugly. 

Bart