International audienceIn this communication, we describe a methodologic tool (software) that give instruction to design the coil winding of low voltage machines fed by inverters. The aim of this tool is to bring useful information to the coil manufacturer who has, first, to respect the size of the slots, the total copper section (slot occupancy) and the coil voltage that are imposed by the motor designer. Then, to increase the PDIV between turns and between turns and ground to the highest value. For that purpose, by using a numerical simulation that takes into account the Paschen's law, the developed software will provide how to choose and arrange the enameled wires in the slots: random or form-wound coils, wires shape (round or rectangular), number of wires in parallel by turn, insulation thickness (grade), turns arrangement,... up to find the best solution that allow to respect both motor designer and PDIV constraints. Some practical examples will be given to prove the efficiency of such a tool

Collin, Philippe

Lefèvre, Yvan

Malec, David

English

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HAL Id: hal-02360834
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Submitted on 13 Nov 2019
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Tool to design the primary electrical insulation system
of low voltage rotating machines fed by inverters
Philippe Collin, David Malec, Yvan Lefèvre
To cite this version:
Philippe Collin, David Malec, Yvan Lefèvre. Tool to design the primary electrical insulation system
of low voltage rotating machines fed by inverters. 2018 IEEE Electrical Insulation Conference (EIC),
Jun 2018, San Antonio, United States. pp.0. ￿hal-02360834￿
Any correspondence concerning this service should be sent to the repository administrator: 
staff-oatao@listes-diff.inp-toulouse.fr 
To link to this article : DOI:10.1109/EIC.2018.8481037 
URL : https://doi.org/10.1109/EIC.2018.8481037 
Open Archive Toulouse Archive Ouverte (OATAO) 
OATAO is an open access repository that collects the work of Toulouse 
researchers and makes it freely available over the web where possible.  
This is an author-deposited version published in: http://oatao.univ-toulouse.fr/ 
Eprints ID: 24563 
To cite this version: Collin, Philippe  and Malec, David  and Lefèvre, 
Yvan  Tool to design the primary electrical insulation system of low 
voltage rotating machines fed by inverters. (2018) In: 2018 IEEE 
Electrical Insulation Conference (EIC), 17 June 2018 - 20 June 2018 (San 
Antonio, United States) 
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2018 Electrical Insulation Conference (EIC), San Antonio, TX, USA, 17-20 June 2018
4OOL TO DESIGN THE PRIMARY ELECTRICAL INSULATION 
SYSTEM OF LOW VOLTAGE ROTATING MACHINES FED BY 
INVERTERS
simulations performed with Ansys Mechanical APDL will 
justify the use of such a tool. 
....... l\.1� �ul(lK; 
hne-b�foflœlb 
Fig 1. Electromechanical chain of full electric aircraft 
li. SLOTMODELLING
The model of the slot is a first level one. One considers 
a slot whose siz.es are hs1o1,tor 1.4 cm by Ls10r=5 mm. The slot is 
supposed to carry two phases. In this work only one phase is 
studied. The slot is then divided in two and only the lower half 
is drawn on Ansys Mechanical APDL as can be seen in Fig 2. 
The choice is made to consider 8 conductors per slot and per 
phase. The different nominal diameters are chosen so that the 
filling factor is close to 0.2 in order to have lot of free space in 
the slot. In all the numerical simulations, the slot sizing and the 
copper cross section remain constant . 
There are two kinds of interface: conductor/conductor 
and conductor/slot. These interfaces are presented in Fig 3. 
L,,ot 
Fig 2. Slot cross section 
Mylar 
Slot 
h,lot 
Fig 3. Interfaces (left: conductor/slot, right: cooductor/conductor) 
Ill. FIRsTLOOK ON 1HE TOOL 
The tool is coupling Matlab 2016 with Ansys Mechanical 
APDL. Fig 5 presents the different steps in order to determine if 
PD may exist. First of all, the parameters are typed in a Matlab 
script. This script then executes the Ansys Mechanical APDL 
model which proceeds to an electrostatic solution. The problem 
is solved in tenu of scalar electric potential V. Let's remind that 
under the following hypothesis of a linear analysis this potential 
V and the electric field E are linked by (1) [4]: 
Ea=-grad(V) (1) 
For each interface, the potential drops other the distances d 
is computed on Matlab. The Vsimu(d) curves obtained are then 
compared to the Paschen's curve with p the pressw-e equals to 1 
bar. If Vsimu(d;) � VPascben(d;) there are probably PD at the 
distance d;. 
This Paschen's curve is the experimental one measured in 
the air by Dakin [5]. The measurement was performed between 
2 plate metallic electrodes. This experimental curve is different 
from the theoretical one usually found in the literature. The latest 
considers a uniform electric field E between the electrodes and 
consists in reflecting the Townsend breakdown mechanism in 
gazes; the ionization process is can-ied by "primary electron" 
and "secondary electron" emission at the cathode by ion 
bombardrnent [6]. The experimental curve however takes into 
account other phenomenas such as photoionization, the 
ionization by light. It explains why the minimums are not the 
same on both curves. 
As it was previously indicated, this experimental curve is 
obtained using 2 plate metallic electrodes. However, in the 
model presented here the conductors are covered with a 
polyimide (Pl) layer. This changes the ionization mechanism 
especially the value of the secondary electron emission at the 
cathode. This coefficient is usually designed with y in the 
literature. It is the ratio of the number of electrons leaving the 
cathode over the number of incoming ions (at the cathode). It is 
easy to calculate analytically y with metallic electrodes but with 
electrodes covered in polymer the only way to determine it is to 
measure it [7] due to the complexity of the involved mechanism. 
Besides, in the model the interfaces are not plane/plane but 
rather cylindrical/cylindrical (between conductors) or 
cylindrical/plane (between conductor and slot). 
As a first level approach the hypothesis have been done to 
consider a constant and straight electric field E at each interface 
(i.e interface plane/plane). Referring to [3], for distances 
d�l mm, the error on the electric field length is lower than 20%. 
For upper distances, the electric field cannot be considered as 
unifonn, so one cannot use Paschen's curve to detennine the 
breakdown voltage of the air in these interfaces. ln  this 
communication, the electric field is supposed uniform (i.e 
dslmm). Moreover, the experimental measurement of the y 
coefficient between 2 round conductors covered in Pl has yet to 
be clone. In consequence, the experimental Paschen's curve 
given by Dakin will be used as criteria of PD existence in this 
work. 
10·1 '--------------' 
IO
..) 
10'
1 
10"
1 
t0
° 10
1 tcf lif 
pd lkir.nun) 
Fig 4. Paschen's cwves 
Parameters entry 
Numerical simulation 
Pick up of the voltage 
values on conductors 
and slot 
Computation of V ,muid) 
curve in each zone 
Design validated 
� Matlab 
� Ansys 
Fig 5. Overview of the process 
IV. NUMERICAL SIMULATIONS 
ln this paragraph, 4 cases are presented which 
illustrates the use of this tool. As it has been introduced in part 
2, the main idea is to compared the computed V simu( d) curves 
with the Paschen's cw-ve. First the slot has been divided in 
zones (Fig 6). Each zone represents either a 
conductor/conductor or a conductor/slot interface. ln  ail the 
coming curves only the zones with the highest stress (i.e closer 
to the Paschen's cw-ve) have been retained. 
Ali the simulations have been performed under the following 
hypothesis: 
-a star winding machine fed by an inverter working on full wave
modulation.
-DC voltage bus is U1,us=690V.
-one coi! per phase per slot so the voltage drop amplitude
between the first and the last tum of the coi! is equal to the 
single-phase voltage amplitude:
Vcoil �*.Jz 488V
2 
(2) 
However, the worst case which can happen during the 
transient regime is taken into account by considering an 
overshoot on the coi! corresponding to twice the DC bus 
voltage. So, the voltage amplitude applied on the coi! is 
V max=976V. Moreover, short coi! hypothesis is clone so that the 
voltage drop between 2 consecutive turns is linear. At last it is 
reminded that the filling factor is chosen close to 2. 
Fig 6. Zones under study 
A. Tums arrangement
The first simulation consists in studying the influence of
tums arrangement. For that 3 configurations have been 
investigated (Fig 7). The nominal diameter of the copper wires 
is 1.06 mm and the insulation layer is e=l 7 µm [9]. Mylar 
thickness is fixed to 100 µm [8]. Numbers inside the copper 
wires refer to the tum number (i.e: 1 is the first turn and 8 is the 
Jast one). The red rectangles designated the focused zones (i.e: 
zones 1, 11 and 21 ). The 3 configurations have been chosen in 
the way to make the turn shift (green numbers) vary between 2 
adjacent tums. Results are presented on Fig 8 and summarized 
on Table 1 (values taken at d=O.0lmm). One notices that in 
zone 21 the voltage value at d=0.01 mm remains constant 
whatever the case. That is because the turn drop at this interface 
does not change. The same can be said for the voltage value of 
zone 1 in the better and optimal case. 
Zone V(d=0.0lmm) wont V(d=0.0lmm) V(d=0.0lmm) optimal 
case (kV) better case case (kV) 
(kV) 
1 0.543 0.078 0.078 
10 0,337 0,253 0,168 
21 0.183 0.183 0.183 
Zone Vworst Vbetter Vbetter Voptlmal Vworst Voptlmal 
Uoo•--•• frh•H•- Uoo•-•• 
1 86% 0% 86% 
10 25% 34% 50% 
21 0% 0% 0% 
Table 1. Voltage values (top) and voltage reduction (low) for 3 tums 
arrangement 
Fig 7. 3 tums arrangement top left worst case, top rigbt better case, low: 
optimal case 
� s 
ô 
> 
--t-Paschen curve 
-+-Vsimu(d) 20ne 1 (worst) 
-+-Vsimu(d) zone 1 (better) 
· +-Vsimu(d) zone 1 ( optimal) 
/...-­
/ 
102 L.......-------------' 
104 102 Irfl I<r Iif 
pd [bar.mm] 
j 100 � 
1s / 
102c......--�-----------' 
10 4 102 10° 102 104 
pd [bar.mm] 
--t-Paschen curve 
[ 
102 
-Vsimu(d) zone 10 (worst) 
-+-Vsimu(d) zone 10 (better) 
� s 
·+-·Vsimu(d) zone 10 (optimal) 
100 
102 
104 10 2 ,rP 102 104 
pd [bar.mm] 
Fig 8. V,;..,(d) vs v-(d) in zones 1 (top), 21 (middle) and 10 (low) for 
different tums arrangement 
B. Grade influence
Here the winding is formed of 8 wires which nominal
diameter is 1.12 mm. They are connected so that they form 2 
turns (1 and 2) as shown in Fig 9. Mylar thickness remains fixed 
to 100 µm [8]. The results obtained in zone 16 are presented in 
Fig 10 and are summarized in the following table: 
Zone V (d=0.027 mm) V (d=0.027 mm) V (d=0.0027 mm) 
min erade 3 averaee erade 3 max erade 3 (e=64 
(e=49 µm) [9) (e:56.Sµm) j!m)[9) 
16 0.514 kV 0.48kV 0.45 kV 
Zone Vml-ngdl - vavgg,t1.3 1 vavg6dl - vmax,9dl 1 Vmlng43 -vmaxg43 VmL-n� Vavo .. ,n Vml-n .n 
16 6.6% 1 6.3% 1 12.5% 
Table 2. Voltage values (top) and voltage redue bon (low) for 3 enamel 
thickness 




Tool to design the primary electrical insulation system of low voltage rotating machines fed by inverters

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Tool to design the primary electrical insulation system of low voltage rotating machines fed by inverters

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