Jean-Marc Lupin

A comparison of electric and dielectric properties of standard and high-crystallinity polypropylene films

The dielectric properties of two grades of Bi-oriented isotactic polypropylene (BOiPP) are studied, using a variety of techniques: breakdown field measurements, dielectric spectroscopy, thermally stimulated depolarization currents, dc conduction currents. Standard (STPP) and high-crystallinity (HCPP) polypropylene films are investigated. Measurements are carried out over a wide temperature range, up to (-150°C/ +125°C). Breakdown field in both materials show a very small difference. On the other hand, dielectric losses and dc conduction currents are significantly lower in HCPP. Both materials show a decrease of dielectric losses versus temperature in the range (20-90°C), favorable for the application to ac power capacitors. The analysis of dc currents allows to evidence two main conduction mechanisms: (i) below 80°C in both materials, a hopping mechanism due to motion of electrons occurring in the amorphous phase; (ii) above 80°C, an ionic conduction in HCPP and a hopping conduction in STPP.

Metallized Film Power Capacitors End-of-Life Study Through Monitored Destruction Tests

A wide range of experiments was performed on metallized film capacitors. The monitoring of destruction tests was used to analyze the electrical properties of artificial critical defects. It is shown herein that these defects in the windings of the capacitors have a wide range of electrical properties and the behavior of the capacitor in the test is strongly related to these properties. A model is proposed to describe the degeneration of dielectric failure, the use of this model can help to predict the behavior of capacitors when they reach the end of life and to a more accurate design of the protection systems.

Relationship between structure and dielectric properties of Bi-oriented isotactic polypropylene films for capacitors

This work reports on the relationship between structure and dielectric properties of biaxially oriented polypropylene. The morphology of semi-crystalline bioriented isotactic polypropylene (BOiPP) films is investigated using Wide Angle X-ray Diffraction (WAXD) and Polarized Optical Microscopy (POM). A β-orthorhombic structure, with a crystallinity ratio of about 46%, and a “Crater” morphology of the β-form is identified. Dielectric properties are measured by Broadband Dielectric Spectroscopy (BDS) over a wide temperature range (-150°C to 125°C). Since the dissipation factor of the PP is very low, special care was taken to obtain valid data. Two main relaxation processes are observed: a α-relaxation peak associated to the glass transition temperature (Tg) at low frequency and temperature about -7°C, and a broad β*-relaxation at high frequency at about -60°C, attributed to CH orientation. The variation of the dissipation factor versus sample thickness (from 3.8 μm to 11.8 μm) is correlated and explained by the increase of crystallinity ratio at larger thicknesses.

Power Quality Improvements for an Electrical System with an Automobile Shredder

The quality of the power supplied by utilities today is effectively defined in the harmonic standards adopted by many countries or by local utility codes. This is primarily due to user demands for quality power so that user power interruptions are minimized. Presented are numerous possible solutions to address flicker and a case study for an automobile shredder from the planning stages through measurements after installation. The solution chosen for this application will be discussed and presented.