scholarly journals Design of inorganic coils for high temperature electrical machines

Open Physics ◽  
2019 ◽  
Vol 17 (1) ◽  
pp. 698-708 ◽  
Author(s):  
Hamed Elmadah ◽  
Daniel Roger ◽  
Noureddine Takorabet
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Equivalent Circuit ◽  
High Frequency ◽  
Electrical Machines ◽  
Nickel Layer ◽  
Voltage Distribution ◽  
Frequency Model ◽  
Coil Structure ◽  
Fast Transients

Abstract The paper deals with a high frequency model of inorganic coils used to build high temperature (HT∘) motor. The HT∘ wire has a nickel layer that protects the copper against oxidation and a thin inorganic coating, which has poor electrical and mechanical properties. Therefore, the coils must be designed with a special care for getting a good distribution of turn-to-turn voltage during the fast transients excited by the steep fronted voltages of the PWM inverter.A specific coil structure is proposed and a high frequency (HF) equivalent circuit able to compute the turn-to-turn voltages during transients. The voltage distribution between the coils of a stator phase is also detailed.

Voltage distribution in inorganic insulation windings for high-temperature motors

2016 ◽  
Vol 35 (6) ◽  
pp. 2074-2086 ◽  
Author(s):  
Daniel Roger ◽  
Vadim Iosf ◽  
Sylvain Babicz
Keyword(s):  
High Temperature ◽  
Equivalent Circuit ◽  
Copper Wire ◽  
Transient State ◽  
Voltage Distribution ◽  
Anodized Aluminum ◽  
Content Type ◽  
Aluminum Strip ◽  
Starting Point ◽  
Electronic Switches

Purpose The purpose of this paper is to present a method for computing voltage spikes endured by the insulation of the first coils of high-temperature (HT°) synchronous machines fed by PWM inverters that deliver fast-fronted voltage pulses. Design/methodology/approach The transient state following each steep edge is computed by SPICE using the global high-frequency (HF) equivalent circuit of the motor winding. This equivalent circuit is automatically built using the proposed elementary coil model. Two inorganic HT° technologies are compared: the first one uses a round copper wire insulated by a thin ceramic layer and the second one is made with an anodized aluminum strip. Findings The winding made with an anodized aluminum strip, which has a higher turn-to-turn capacitance, yields a better voltage distribution between coils of the machine. Research limitations/implications The elementary coil equivalent circuit is computed from impedance measurements performed on an elementary coil. Another starting point could be developed with an FE analysis to determine the parameters of the HF equivalent circuit, which would avoid the need for a prototype coil before the machine design. Practical implications For inorganic motors, the insulation layers have poorer electrical characteristics compared with standard organic ones. Therefore, the computation of voltage spikes distribution along the coils of each phase represents a major issue in the design of HT° machines. Originality/value The presented approach is a step toward the design of HT° (400-500°C) actuators fed by PWM inverters based on fast SiC electronic switches.

Voltage distribution in the windings of high temperature inverter-fed motors

2018 ◽  
Vol 37 (5) ◽  
pp. 1824-1836 ◽  
Author(s):  
Daniel Roger ◽  
Ewa Napieralska-Juszczak
Keyword(s):  
High Temperature ◽  
Equivalent Circuit ◽  
Time Windows ◽  
Critical Time ◽  
Equivalent Circuits ◽  
State Variables ◽  
Voltage Distribution ◽  
Content Type ◽  
Pwm Inverter ◽  
Magnetic Couplings

Purpose High-temperature (HT°) motors are made with inorganic coils wound with a ceramic-coated wire. They must be carefully designed because the HT° insulating materials have a lower breakdown voltages than the polymers used for insulating standard machines. Design/methodology/approach The voltage distribution between stator coils is computed with high-frequency (HF) equivalent circuits that consider the magnetic couplings and the stray capacitances. Two time scales are used for getting a fast computation of very short voltage spikes. For the first step, a medium time scale analysis is performed considering a simplified equivalent circuit made without any stray capacitance but with the full PWM pattern and the magnetic couplings. For the second step, a more detailed HF equivalent circuit computes voltage spikes during short critical time windows. Findings The computation made during the first step provides the critical time windows and the initial values of the state variables to the second one. The rise and fall time of the electronic switches have a minor influence on the maximum voltage stress. Conversely, the connection cable length and the common-mode capacitances have a large influence. Research limitations/implications HF equivalent circuits cannot be used with random windings but only to formed coils that have a deterministic position of turns. Practical implications The proposed method can be used designing of HT° machine windings fed by PWM inverter and for improving the coils of standard machine used in aircraft’s low-pressure environments. Originality/value The influence of grounding system of the DC link is considered for computing the voltage spikes in the motor windings.

scholarly journals Aging monitoring of electrical machines using winding high frequency equivalent circuits

Open Physics ◽  
2019 ◽  
Vol 17 (1) ◽  
pp. 670-677
Author(s):  
Sonia Ait-Amar ◽  
Daniel Roger ◽  
Serghei Savin
Keyword(s):  
Equivalent Circuit ◽  
High Frequency ◽  
Impedance Analysis ◽  
Electrical Machines ◽  
Monitoring Method ◽  
Insulation Aging ◽  
Capacitance Variation ◽  
Resonance Frequencies ◽  
Predetermined Level ◽  
Frequency Behavior

Abstract This study defines a monitoring method based on impedance analysis in the upper part of the spectrum. It focuses on the analysis of the high frequency behavior of electrical machines windings considering the turn-to-turn capacitance variations (delta-C) due to insulation aging. An equivalent circuit is automatically generated from the turn arrangements in coils; parameters are computed considering the coil shape and the characteristics of insulation materials. PSpice analysis of the equivalent circuit yields the resonance frequencies to be monitored. With this software and a database giving the relationship between the turn-to-turn capacitance variation delta-C and the reduction of insulation performances due to aging, it is possible to build a monitoring system able to produce an alert when the probability of failure becomes higher than a predetermined level.

Lattice Imaging of Grain Boundaries in Ceramics

1977 ◽  
Vol 35 ◽  
pp. 114-115
Author(s):  
D. R. Clarke ◽  
G. Thomas
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Silicon Nitride ◽  
Grain Boundaries ◽  
High Temperature Strength ◽  
Current Interest ◽  
Lattice Imaging ◽  
Special Significance ◽  
Structural Applications ◽  
Refractory Ceramics

Grain boundaries have long held a special significance to ceramicists. In part, this has been because it has been impossible until now to actually observe the boundaries themselves. Just as important, however, is the fact that the grain boundaries and their environs have a determing influence on both the mechanisms by which powder compaction occurs during fabrication, and on the overall mechanical properties of the material. One area where the grain boundary plays a particularly important role is in the high temperature strength of hot-pressed ceramics. This is a subject of current interest as extensive efforts are being made to develop ceramics, such as silicon nitride alloys, for high temperature structural applications. In this presentation we describe how the techniques of lattice fringe imaging have made it possible to study the grain boundaries in a number of refractory ceramics, and illustrate some of the findings.

TEM Studies of Grain Boundary Films in Si3N4 Ceramics

1991 ◽  
Vol 49 ◽  
pp. 930-931
Author(s):  
H.-J. Kleebe ◽  
J.S. Vetrano ◽  
J. Bruley ◽  
M. Rühle
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Silicon Nitride ◽  
Hot Isostatic Pressing ◽  
Amorphous Film ◽  
Liquid Phase Sintering ◽  
Second Phase ◽  
High Temperature Mechanical Properties ◽  
Triple Points ◽  
Boundary Films

It is expected that silicon nitride based ceramics will be used as high-temperature structural components. Though much progress has been made in both processing techniques and microstructural control, the mechanical properties required have not yet been achieved. It is thought that the high-temperature mechanical properties of Si3N4 are limited largely by the secondary glassy phases present at triple points. These are due to various oxide additives used to promote liquid-phase sintering. Therefore, many attempts have been performed to crystallize these second phase glassy pockets in order to improve high temperature properties. In addition to the glassy or crystallized second phases at triple points a thin amorphous film exists at two-grain junctions. This thin film is found even in silicon nitride formed by hot isostatic pressing (HIPing) without additives. It has been proposed by Clarke that an amorphous film can exist at two-grain junctions with an equilibrium thickness.

AEM of reaction-bonded SiC

1992 ◽  
Vol 50 (1) ◽  
pp. 344-345
Author(s):  
K Das Chowdhury ◽  
R. W. Carpenter ◽  
W. Braue
Keyword(s):  
Mechanical Properties ◽  
Phase Transformation ◽  
High Temperature ◽  
Epitaxial Growth ◽  
Liquid Silicon ◽  
Structural Ceramic ◽  
Few Data

Research on reaction-bonded SiC (RBSiC) is aimed at developing a reliable structural ceramic with improved mechanical properties. The starting materials for RBSiC were Si,C and α-SiC powder. The formation of the complex microstructure of RBSiC involves (i) solution of carbon in liquid silicon, (ii) nucleation and epitaxial growth of secondary β-SiC on the original α-SiC grains followed by (iii) β>α-SiC phase transformation of newly formed SiC. Due to their coherent nature, epitaxial SiC/SiC interfaces are considered to be segregation-free and “strong” with respect to their effect on the mechanical properties of RBSiC. But the “weak” Si/SiC interface limits its use in high temperature situations. However, few data exist on the structure and chemistry of these interfaces. Microanalytical results obtained by parallel EELS and HREM imaging are reported here.

Sign in / Sign up

Export Citation Format

Share Document