ANSOFT INTRODUCES NEW DYNAMIC ELECTROMAGNETIC SIMULATOR FOR
ELECTROMECHANICAL SYSTEMS

Maxwell EM System Simulator performs accurate time domain simulation of
electromagnetic devices including mechanical motion and SPICE models of
driver and load circuitry.

DETROIT MI, AUTOFACT, November 14, 1994 --Ansoft Corporation, the leading
supplier of electromagnetic field simulation based electromechanical (EM)
and signal integrity (SI) design tools, announced today that it is adding
a new product, the Maxwell EM System Simulator, to its electromechanical
product line. The new simulator enables electromagnetic device
characteristics to be combined with equations of motion and circuit
excitation to predict the behavior of the complete electromechanical
system. Typical applications include:

* Electric motor systems. Phase voltages, currents, and motor torque are
computed as functions of rotor position.

* Transformers. Voltages and currents are computed as a function of time.
This analysis includes the nonlinear variations in flux.

* Actuators. The position and velocity of the moving parts are computed as
are the voltage and current waveforms in the coils and drive circuitry.
Accounts for all the electromagnetic forces in the actuator, the equations
of motion, and circuit excitations.

Ansoft's founder Dr. Zoltan Cendes said, "Ansoft is offering a unique
solution to the problem of predicting the temporal behavior of
electromechanical systems with moving parts. For a decade, we have focused
on extracting accurate parameters characterizing electromagnetic behavior
at the component level. The Maxwell EM System Simulator employs Basis
Evaluation State Space Techniques (BESST) to combine parametric Finite
Element Analysis with SPICE based circuit simulation to model
electromechanical devices with their associated drive and load
circuitry."

"The Maxwell EM System Simulator leverages our expertise and experience
with our proven EM field solvers. These products accurately model
complicated structures with detailed geometry and saturation effects. This
ensures accurate and reliable models for inductance, resistance, force,
torque, flux linkage, and induced-back EMF and enables us to meet our
continuing commitment to help our customers expand the scope of their
pre-prototype design phase by including SPICE models and load circuitry,"
added Dr. Cendes.

The Maxwell EM System Simulator supports a wide variety of electrical
devices, including nonlinear elements and moving parts. The time
integration and nonlinear iteration techniques used for circuit simulation
in SPICE are well-suited for electromechanical systems, when the physical
parameters are represented using circuit voltages and currents. The
simulator comes with an enhanced version of SPICE (called Maxwell SPICE)
to effectively model an electromechanical system using only electrical
elements.

According to Dr. Ren Wang, Senior Technical Analyst at the Motor Technology
Development group of Black & Decker, "Ansoft's Maxwell electromechanical
products offer the most accurate link between parametric finite element
analysis and system simulation. The parametric solutions from the Maxwell
EM 2D Field Simulator can be automatically converted to circuit models
that are solved by Maxwell SPICE. SPICE uses these models to represent the
actual electromechanical system parameters at each step in the transient
analysis."

The EM System Simulator includes a new schematic capture module to drive
SPICE simulations. This module offers graphical editing of electrical
circuit models, with automatic node numbering and either interactive or
batch execution of SPICE from the schematic. Signal plotting and other
post processing features are included.

The schematic capture module provides a convenient way to use the SPICE
models and subcircuits derived from Maxwell EM Field Simulators for
nonlinear inductors, transformers, rotating machines, and other devices.
User-defined or third-party models and subcircuits are incorporated in the
schematic capture module as "black boxes", as long as they adhere to
Berkeley SPICE syntax. This also opens the door to other compatible SPICE
simulators such as Analogy's SABER, and Intusoft's IsSPICE.
Ansoft's new Maxwell EM System Simulator is being demonstrated on PCs
running Windows NT and UNIX workstations from SUN, HP, IBM and SGI for the
first time at Autofact in Detroit MI, November 15 through 17, 1994 at
Booth #832.

The Maxwell EM System Simulator will be available Q2 95 with a 2D option
priced at US $24,900 ($19,900 on PCs). The 2D option is followed by the
complete 3D option (which includes 2D) priced at US $44,900 for both
workstations and PCs. Current customers of Maxwell EM 2D or 3D Field
Simulator can easily upgrade to the EM System Simulator.

Ansoft Corporation, the leading supplier of electromagnetic field
simulation design tools, has over 1000 customers in the United States,
Europe and Asia Pacific, with customers in the automotive, magnetic
recording, medical, semiconductor, communications, computer and aerospace
sectors. Founded in 1984 by Zoltan Cendes, an internationally renowned
authority in electromagnetics, Ansoft entered the electromechanical market
with Maxwell 2D Field Simulation in 1985 and the signal integrity market
with Maxwell Spicelink in 1992. Ansoft is privately held and headquartered
at Four Station Square, Suite 660, Pittsburgh, PA 15219-1119 USA. Phone
412-261-3200. Fax 412-471 9427. E-mail EMinfo@ansoft.com.
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Maxwell EM System Simulator Application Examples
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Transformers

In nonlinear transformers, the magnitude of the input current affects the
amount of flux linked by the device. The Maxwell EM System Simulator
creates a parametric model as a table with current as a variable to model
this effect. Each row of the table represents different excitation levels
or operating points for the device. Because nonlinear materials are
present, the flux between the coils varies non linearly with the current.
The Simulator generates a circuit model from this table, with self and
mutual inductances representing the transformer. Within the model, as in
the actual device, current magnitude affects the inductances. This
transformer model is compatible with SPICE driver and load models for
transient analysis. The Maxwell EM System Simulator also calculates and
plots the transformer's voltages and currents.

Motors

An electric motor consists of a rotor and a stator in which the flux
linkage and inductance oscillate with rotor position. To model a motor,
the Maxwell EM System Simulator analyzes the field effects at different
rotor positions. The Simulator creates a parametric table with rotor
position as a variable and automatically solves for the resulting
inductances. Using these inductances, the Simulator creates a circuit
model. The controlling variable (rotor position) is taken as an input to
the model (represented by a voltage). The motor and its circuitry are
analyzed using time domain simulation. The drive can contain switches,
diodes, transformers or other standard circuitry. The Maxwell EM System
Simulator calculates and plots the resulting phase voltages, currents and
motor torque.

Actuators

The movement, positioning and activation of electromagnetic actuators are
controlled by the electromagnetic forces in the actuator, the equations of
motion for the moving parts, and the circuit excitation. The Maxwell EM
System Simulator builds a model for simulating the actuator dynamics by
coupling the electromagnetic field solution with the differential
equations governing the actuator dynamics and the electronic circuits.
First, the simulator creates a parametric model of the actuator using
position and excitation level as variables. It then automatically solves
for the forces and inductances in the actuator as a function of these
parameters. The position and velocity are represented by equivalent
circuit parameters. This allows the equations of motion, which are
represented as differential equations, to be conveniently modeled in
SPICE. This model of the equations of motion can be defined in the
simulator, and then automatically combined with the SPICE model of the
drive circuitry and the nonlinear, position dependent actuator inductance
model. Transient simulation of the coupled system in SPICE provides a
number of useful design parameters including:

* values and plots of the position and velocity of the moving
  parts
* voltage and current waveforms in the coils and drive circuitry.

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