For Paul Schoen and John Fields - autotransformer SPICE models.

Following the exchanges on SEB, about autotransformers, and turns ratio, I wrote these models.

The subckts should run on any SPICE which supports .param and rser/rpar.

The .asy files are for LTspice. The symbols should pick up the subckts without any need for a .lib directive.

The first is simpler, requiring primary inductance, turns ratio, and primary resistance.

The second example attempts to incorporate separate copper and iron losses, and leakage inductance.

These could start as a base for developing multi-tapped, or compound (auto plus double-wound) transformer models. I think Paul uses those.

TURN OFF WRAPPING BEFORE COPYING!

autotransformer.sub: Goes in /lib.sub

• Autotransformer with single tap.

*

• Params: TR Turns Ratio pri/sec

* Lpri Inductance of primary * Rpri Resistance of primary

• Resistance of secondary is

* automatic from turns ratio

• Primary means start to finish

• Secondary means tap to finish

• .SUBCKT AUTOTRANSFORMER Start Tap Finish L1 Start Tap {(1-(1/TR))**2*Lpri} Rser={(1-1/TR)*Rpri} L2 Tap Finish {(1/TR)**2*Lpri} Rser={(1/TR)*Rpri} K1 L1 L2 1 .ENDS

autotransformer.asy: Goes in /lib/sym

Version 4 SymbolType BLOCK RECTANGLE Normal -63 -52 64 56 TEXT -56 -32 Left 2 Params: TEXT -19 -17 Left 2 TR TEXT -18 -4 Left 2 Lpri TEXT -19 9 Left 2 Rpri WINDOW 0 -1 -56 Bottom 2 WINDOW 3 2 59 Top 2 SYMATTR Value AUTOTRANSFORMER SYMATTR Prefix X SYMATTR ModelFile C:\Program Files\LTC\LTspiceIV\lib\sub\autotransformer.sub SYMATTR Description Single-tapped autotransformer. PIN 64 -32 RIGHT 8 PINATTR PinName Start PINATTR SpiceOrder 1 PIN 64 0 RIGHT 8 PINATTR PinName Tap PINATTR SpiceOrder 2 PIN 64 32 RIGHT 8 PINATTR PinName Finish PINATTR SpiceOrder 3

autotransformer_advanced.sub: Goes in /lib/sub

*

• Autotransformer with single tap.

*

• Params: TR Turns Ratio pri/sec

* Lpri Inductance of primary * LI Leakage Inductance * RCu Copper losses

• RFe Iron Losses

*

• Primary means start to finish

• Secondary means tap to finish

• .SUBCKT AUTOTRANSFORMER_ADVANCED Start Tap Finish L1 N001 Tap {(1-(1/TR))**2*Lpri} Rser={(1-1/TR)*RCu} Rpar={(1-1/TR)*RFe} L2 Tap 0 {(1/TR)**2*Lpri} Rser={(1/TR)*RCu} Rpar={(1/TR)*RFe} Lleakage Start N001 {Ll} Rser=0 Rpar=0 K1 L1 L2 1 .ENDS

autotransformer_advanced.asy: Goes in /lib/sym

Version 4 SymbolType BLOCK RECTANGLE Normal -97 -72 112 40 TEXT -91 -45 Left 2 TR Turns Ratio TEXT -91 -33 Left 2 Lpri Inductance of primary TEXT -91 -19 Left 2 LI Leakage Inductance TEXT -91 -6 Left 2 RCu Copper losses TEXT -91 6 Left 2 RFe Iron Losses TEXT -91 -57 Left 2 Params: WINDOW 0 7 -72 Bottom 2 WINDOW 3 8 24 Top 2 SYMATTR Value AUTOTRANSFORMER_ADVANCED SYMATTR Prefix X SYMATTR ModelFile autotransformer_advanced.sub PIN 112 -48 RIGHT 8 PINATTR PinName Start PINATTR SpiceOrder 1 PIN 112 -16 RIGHT 8 PINATTR PinName Tap PINATTR SpiceOrder 2 PIN 112 16 RIGHT 8 PINATTR PinName Finish PINATTR SpiceOrder 3

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