VM121

VM121
Voltage Forced Coil

Overview

Reference:	P.J. Leonard and D. Rodger, “Voltage Forced Coils for 3D Finite-Element Electromagnetic Models”, IEEE Transactions on Magnetics, Vol. 24, No. 6 (1988).
Analysis Type(s):	Transient Analysis (ANTYPE=4)
Element Type(s):	3D 20-Node Electromagnetic Solid (SOLID236)
Input Listing:	vm121.dat

Test Case

A circular coil of rectangular cross-section is modeled between two aluminum plates (first solution) and in free-space (second solution). A transient analysis is performed with a 20 volt step excitation. The total current flowing through the coil is calculated.

Material Properties

Geometric Properties

Loading

µr = 1.0 (Air)

µr = 1.0 (Plate)

µr = 1.0 (Coil)

R = 12.4 Ω (Resistance of Coil)

R = 3 x 10^-8 Ω-m (Resistivity of Plate)

Coil:

n = 700 turns

R_i = 0.087 m (Inner Radius)

H = 0.028 m (Height)

R_o = 0.116 m (Outer Radius)

Plates:

0.24 x 0.24 x 0.0127 m³

Gap = 0.03435 m

V = 20 Volt

Analysis Assumptions and Modeling Notes

This model solves the voltage forced coil problem using 20-node electromagnetic SOLID236 elements with different key options:

SOLID236 elements with KEYOPT (1) = 0 for air (AZ).
SOLID236 elements with KEYOPT (1) = 1 for plate (AZ, VOLT)
SOLID236 elements with KEYOPT (1) = 2 for stranded coil (AZ, VOLT, EMF)

A 1/8 symmetric 3D model is constructed (Figure 171: Finite Element Mesh of the Coil and Plate). The step voltage input is applied on the coil. The current source density in the coil and the plate are shown in Figure 173: Current Density in the Plate and Figure 174: Coil Current vs. Time .

The target data is obtained from Figure 4 in the reference paper.

Figure 171: Finite Element Mesh of the Coil and Plate

Figure 172: Current Density in the Coil

Figure 173: Current Density in the Plate

Figure 174: Coil Current vs. Time

Results Comparison

Time=1x10^-2 sec	Target	Mechanical APDL	Ratio
Current in coil with plate (A)	1.160	1.156	0.997
Current in coil in free space (A)	0.970	0.975	1.005

Time=4x10^-2 sec	Target	Mechanical APDL	Ratio
Current in coil with plate (A)	1.510	1.512	1.002
Current in coil in free space (A)	1.570	1.578	1.005

Time=7x10^-2 sec	Target	Mechanical APDL	Ratio
Current in coil with plate (A)	1.580	1.586	1.004
Current in coil in free space (A)	1.610	1.611	1.000