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Re: [TCML] MOT Measurements



Hi Finn, All (Ted, Herwig),

Finn, I went through Tera Ranta equations against my own and then ran the simulations measuring the primary current with the secondary shorted (a great test for accuracy). I simply changed the source voltage as appropriate to the measurement and then changed the L1, L2, and K values associated to the transformer as indicated by Tera's values and my own (hope this table doesn't wrap or have formatting issues).

Freq Vin (m) Vout (m) L1 Ios (m) L1 Isc (m) L2 Isc (m) Winding Ratio Vout (calc) Inductance Ratio (calc) L1 Reactance (calc) Bart L1 (calc) Bart L2 (calc) Tera L1 (calc) Tera L2 (calc) Tera k (calc) Bart k (calc) 60 10.14 182 0.178 1.72 0.096 18 182.52 324 57.0 0.1511 48.96 0.1511 48.59 1.001 0.947 60 20.00 365 0.220 3.31 0.150 18 360.00 324 90.9 0.2411 78.13 0.2411 97.11 0.909 0.966 60 30.20 563 0.270 5.00 0.240 18 543.60 324 111.9 0.2967 96.13 0.2967 115.23 0.946 0.973 60 40.20 747 0.310 6.62 0.320 18 723.60 324 129.7 0.3440 111.45 0.3440 132.23 0.948 0.976 60 50.10 928 0.360 8.42 0.410 18 901.80 324 139.2 0.3692 119.60 0.3692 140.42 0.950 0.978 60 60.20 1123 0.430 10.63 0.530 18 1083.60 324 140.0 0.3714 120.32 0.3714 138.94 0.964 0.980 60 70.20 1321 0.510 13.46 0.680 18 1263.60 324 137.6 0.3651 118.30 0.3651 136.00 0.975 0.981 60 80.00 1476 0.600 16.60 0.860 18 1440.00 324 133.3 0.3537 114.59 0.3537 125.95 0.978 0.982 60 90.10 1681 0.780 24.00 1.120 18 1621.80 324 115.5 0.3064 99.28 0.3064 122.50 0.933 0.984 60 100.00 1812 0.980 29.00 1.320 18 1800.00 324 102.0 0.2707 87.70 0.2707 107.75 0.908 0.983 60 110.10 1971 1.600 36.00 1.600 18 1981.80 324 68.8 0.1825 59.14 0.1825 73.52 0.892 0.978 60 120.20 2071 2.760 43.00 1.880 18 2163.60 324 43.6 0.1155 37.43 0.1155 45.53 0.868 0.967


Above is the measured and calculated values. Note that both Tera and I calc L1 the same in all cases, but L2 changes. Note that k is very different also. This is how the the simulation resulted using Tera' L and k values and my own against real measurements:

Tera (L1 current w/L2 shorted) Bart (L1 current w/L2 shorted) Actual Measured Value
24.149 	1.693 	1.72
1.217 	3.254 	3.31
2.519 	5.016 	5.00
2.998 	6.476 	6.62
3.624 	8.2 	8.42
6.553 	10.77 	10.63
10.24 	13.43 	13.46
13.67 	16.66 	16.60
5.85 	24.3 	24.00
5.34 	28.72 	29.00
7.58 	36.21 	36.00
10.92 	42 	43.00


This is why I am extremely confident in both measurement methods and calculations regarding the transformer. There is no way in hell that my calculations could possibly be as close as they are to real measured values in primary current under shorted conditions unless the transformer model was correct (this means k, L1, and L2 are real).

Tera Ranta's equations do not work. It was a great attempt, but it isn't right (worse than I expected actually). His coupling addition for the L2 equation and coupling itself is where his problem is located.

Just in case the above tables are unreadable due to formatting, here is my spreadsheet:
http://www.classictesla.com/temp/TeraRanta-Bart.xls

Everyone can run the simulations themselves. A simple AC source input at posted AC values, a linear transformer, Rp and Rs of the transformer. Here's a gif of a simple simulator run that identifies source, transformer values, shorted secondary, and where the primary current is inserted. It doesn't get much simpler than this (Microsim).
http://www.classictesla.com/temp/MOT.gif

Take care,
Bart

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