26-06-2012, 11:37 AM
FE-Circuit Coupled Model of Electric Machines for Simulation and
Evaluation of EMI Issues in Motor Drives
FE-Circuit Coupled Model of Electric Machines.pdf (Size: 403.34 KB / Downloads: 26)
INTRODUCTION
HIGH frequency motor models play important roles in the
evaluation of EMI in an integrated motor drive system.
In earlier work by these authors, the high frequency phase variable
model of PM synchronous motor was developed and implemented
in Simulink environment [1]. In this model, the per
phase distributed winding circuit was developed considering the
high frequency effects and then lumped to form the high frequency
winding branch. This branch was connected in parallel
to the low frequency phase variable model to form the high frequency
phase variable model. The phase variable model is a
database representation of the machine’s numerical model and
it allows one to perform dynamic simulation with hardware in
the loop [3].
DISTRIBUTED PARAMETER MODEL OF THE COIL
Simulations were performed on a small 3-phase, 42-V,
10-pole, 0.28-HP, 3600-rpm, 7.8-A PM synchronous motor.
The simulated motor model was built based on its actual
geometry information. The individual turns in each coil were
considered. The motor has double layer windings with random
winding arrangement. There are four coils per phase with each
coil having 13 turns. Therefore, each half slot contains 13 conductors
of wire gauge number 22. All the slots were modeled
so that the effects of geometrical variation in the magnetic
circuit on the machine circuit parameters could be considered.
The machine was modeled to take into consideration the conductor
skin and proximity effects. The resistance value at high
frequency can be much higher than the low frequency value.
Skin effects in the core was also considered by assigning proper
resistivity value. The capacitance effect comes into play at high
frequencies.
REDUCED ORDER MODEL
In this model, reduced order models for resistance, and capacitances
were calculated. Lumping of the parameters was performed
by matrix reduction method [2]. A nodal model was created
in which half of each capacitance is shifted towards the two
ends of the conductor and then the nodal capacitance matrix is
formed from the conductor’s capacitance matrix by recognizing
which elements are connected to each node. The resulting matrix
is of the order 2N. To reduce the order of the model, the
series connected conductors in one slot are lumped to form a
section. In short, the process is shifting of internal capacitances
towards pre-established section nodes.
CONCLUSION
The coupled FE-circuit high frequency electric machine
model for simulating electromagnetic interference in a motor
drive was presented. The model can predict EMI caused by
the ground current and motor terminal overvoltage. Use of this
procedure could prove economical, as it would help designers
develop new motor designs for high frequency operating conditions
numerically. The proposed model can be used as a
computational prototyping tool. Therefore, the development
to design and final product stages can be completed without
the need for repeated build and test procedures in an industrial
environment.