The Arbitrary Inductor model - Revision history

DennisChi: Correct the equation for flux with saturation sharpness parameter "a" to always produce negative flux for negative current.

2024-02-01T17:14:19Z

Correct the equation for flux with saturation sharpness parameter "a" to always produce negative flux for negative current.

Analogspiceman at 23:26, 22 September 2009

2009-09-22T23:26:39Z

Analogspiceman at 03:21, 21 September 2009

2009-09-21T03:21:18Z

Analogspiceman at 03:18, 21 September 2009

2009-09-21T03:18:37Z

Analogspiceman at 02:58, 21 September 2009

2009-09-21T02:58:25Z

Analogspiceman at 00:08, 21 September 2009

2009-09-21T00:08:11Z

Analogspiceman at 23:58, 20 September 2009

2009-09-20T23:58:13Z

Analogspiceman at 23:44, 20 September 2009

2009-09-20T23:44:08Z

Analogspiceman: Created page with 'LTspice allows specifying a behavioral inductance with an expression for the flux. The inductor's current is referred to by the keyword "x" in the expression. Below i…'

2009-09-20T16:58:24Z

Created page with 'LTspice allows specifying a behavioral inductance with an expression for the flux. The inductor's current is referred to by the keyword "x" in the expression. Below i…'

New page

LTspice allows specifying a behavioral inductance with an expression for the flux.  The inductor's current is referred to by the keyword "x" in the expression.  Below is a netlist example of an inductor with simple saturation.

L1 1 0 Flux=1m*tanh(5*x)/5 ; 1mH inductor saturates at 0.2 volt-seconds
I1 0 1 PWL(0 0 1 1) ; supplies unity di/dt so inductance corresponds to voltage
.tran 1
.end

@@ Line 17: / Line 17: @@
 Here this is further extended to add exponential control of saturation "sharpness" where an exponent of a=1 is normal and a>1 is sharper.
-  flux={L*Is}*tanh((x/{Is})**{a})**{1/a} ; a= saturation "sharpness" (1=normal, >1=sharper)
+  flux={L*Is}*sgn(x)*tanh((abs(x)/{Is})**{a})**{1/a} ; a= saturation "sharpness" (1=normal, >1=sharper)
 Note that the parameters for the above expressions must be defined elsewhere upon the schematic, usually as a parameter statement within a [[SPICE Directive]] (SPICE text placed anywhere within the schematic).

@@ Line 1: / Line 1: @@
-LTspice allows specifying a behavioral inductance with an expression for the flux.&nbsp; Here, the inductor's current can be uniquely referred to by the special keyword "x", but otherwise the expression may be completely arbitrary, that is, it may be any valid function of system dynamics (e.g., time and/or node voltages and/or branch currents).
+LTspice allows specifying a behavioral inductance via an expression for inductor flux.&nbsp; Within this expression the inductor's current can be uniquely referred to by the special keyword "x", but otherwise the expression may be completely arbitrary, that is, it may be any valid function of system dynamics (e.g., time and/or node voltages and/or branch currents).
 Below is a netlist example of an inductor with simple saturation.
+<pre>
- L1 1 0 flux=0.33*2*tanh(x/2) ; 330mH inductor "saturates" at 2A (0.66 volt-seconds)
+* 330mH inductor "saturates" at 2A (L*Isat = 0.66 volt-seconds)
- I1 0 1 PWL(0 0 1 1) ; supplies unity di/dt so inductance corresponds to voltage
+L1 0 1 flux=0.33*2*tanh(x/2)
- .tran 0 5 1u 10m ; 5s transient run starting after 1us with 10ms maximum step size
+* I1 supplies unity di/dt so inductance corresponds to voltage
- .end
+I1 0 1 PWL(0 0 1 1)
+* 5s transient run starting after 1us with 10ms maximum step size
-LTspice's behavioral inductor may be parametrized, but the parser requires that all parameters or strictly parametric expressions must be enclosed within ''curly braces''.&nbsp; Strictly parametric expressions may not include "x" (inductor current) or other ''dynamic variables''.&nbsp; Below is a flux expression example of this technique.
+.tran 0 5 1u 10m
   flux={L*Is}*tanh(x/{Is}) ; L= inductance and Is= "saturation" current
-Here this is further extended to add exponential control of saturation "sharpness" where an exponent of 1 = normal and >1 = sharper.
+Here this is further extended to add exponential control of saturation "sharpness" where an exponent of a=1 is normal and a>1 is sharper.
   flux={L*Is}*tanh((x/{Is})**{a})**{1/a} ; a= saturation "sharpness" (1=normal, >1=sharper)
@@ Line 20: / Line 23: @@
   .param L=330mH Is=2A a=3 ; fairly sharp saturation at 2A (the "a" factor is exponential)
-Unlike the standard inductor, which defaults to a series resistance of 1mΩ, the arbitrary inductor has no series resistance unless explicitly specified (ctrl-right mouse button click on the inductor).&nbsp; Also note that the numerical dynamic range of the arbitrary inductor seems to be about 15 decades or so.
+Unlike the standard inductor, which defaults to a series resistance of 1mΩ, the arbitrary inductor has no series resistance unless explicitly specified (ctrl-right-mouse-button-click on the inductor).&nbsp; Also note that the numerical dynamic range of the arbitrary inductor seems to be about 15 decades or so.

@@ Line 16: / Line 16: @@
   flux={L*Is}*tanh((x/{Is})**{a})**{1/a} ; a= saturation "sharpness" (1=normal, >1=sharper)
-Note that the parameters for the above expressions must be defined elsewhere upon the schematic, usually as a parameter statement within a SPICE directive (SPICE text placed anywhere within the schematic).
+Note that the parameters for the above expressions must be defined elsewhere upon the schematic, usually as a parameter statement within a [[SPICE Directive]] (SPICE text placed anywhere within the schematic).
   .param L=330mH Is=2A a=3 ; fairly sharp saturation at 2A (the "a" factor is exponential)
 Unlike the standard inductor, which defaults to a series resistance of 1mΩ, the arbitrary inductor has no series resistance unless explicitly specified (ctrl-right mouse button click on the inductor).&nbsp; Also note that the numerical dynamic range of the arbitrary inductor seems to be about 15 decades or so.

← Older revision		Revision as of 03:18, 21 September 2009
Line 1:		Line 1:
−	LTspice allows specifying a behavioral inductance with an expression for the flux.  ~~The~~ inductor's current ~~''may''~~ be referred to by the keyword "x" ~~in the expression~~, but otherwise it may be completely arbitrary, that is, it may be any valid function of system dynamics (e.g., time and/or node voltages and/or branch currents).	+	LTspice allows specifying a behavioral inductance with an expression for the flux.  Here, the inductor's current can be uniquely referred to by the special keyword "x", but otherwise the expression may be completely arbitrary, that is, it may be any valid function of system dynamics (e.g., time and/or node voltages and/or branch currents).

	Below is a netlist example of an inductor with simple saturation.		Below is a netlist example of an inductor with simple saturation.

@@ Line 1: / Line 1: @@
-LTspice allows specifying a behavioral inductance with an expression for the flux.&nbsp; The inductor's current ''may'' be referred to by the keyword "x" in the expression, but otherwise is completely arbitrary (i.e., may be any valid function of time and/or node voltages and/or branch currents within the simulation).
+LTspice allows specifying a behavioral inductance with an expression for the flux.&nbsp; The inductor's current ''may'' be referred to by the keyword "x" in the expression, but otherwise it may be completely arbitrary, that is, it may be any valid function of system dynamics (e.g., time and/or node voltages and/or branch currents).
 Below is a netlist example of an inductor with simple saturation.
@@ Line 12: / Line 12: @@
   flux={L*Is}*tanh(x/{Is}) ; L= inductance and Is= "saturation" current
-Here this is further extended to add exponential control of saturation "sharpness".
+Here this is further extended to add exponential control of saturation "sharpness" where an exponent of 1 = normal and >1 = sharper.
   flux={L*Is}*tanh((x/{Is})**{a})**{1/a} ; a= saturation "sharpness" (1=normal, >1=sharper)
@@ Line 20: / Line 20: @@
   .param L=330mH Is=2A a=3 ; fairly sharp saturation at 2A (the "a" factor is exponential)
-Unlike the standard inductor, which defaults to a series resistance of 1mΩ, the arbitrary inductor has no series resistance unless explicitly specified (ctrl-right mouse button click on the inductor).&nbsp; Also note that the numerical dynamic range of the arbitrary inductor seems to be about only 15 decades or so.
+Unlike the standard inductor, which defaults to a series resistance of 1mΩ, the arbitrary inductor has no series resistance unless explicitly specified (ctrl-right mouse button click on the inductor).&nbsp; Also note that the numerical dynamic range of the arbitrary inductor seems to be about 15 decades or so.

← Older revision		Revision as of 23:58, 20 September 2009
Line 20:		Line 20:
	.param L=330mH Is=2A a=3 ; fairly sharp saturation at 2A (the "a" saturation factor is exponential)		.param L=330mH Is=2A a=3 ; fairly sharp saturation at 2A (the "a" saturation factor is exponential)

−	Unlike the standard inductor, which defaults to a series resistance of ~~1mOhm~~, the arbitrary inductor has no series resistance unless explicitly specified (ctrl-right mouse button click on the inductor).  Also note that the numerical dynamic range of the arbitrary inductor seems to be about only 15 decades or so.	+	Unlike the standard inductor, which defaults to a series resistance of 1mΩ, the arbitrary inductor has no series resistance unless explicitly specified (ctrl-right mouse button click on the inductor).  Also note that the numerical dynamic range of the arbitrary inductor seems to be about only 15 decades or so.