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ABSTRACT: One of the main factors limiting the reliability of metallized polypropylene capacitors is degradation of the electrode/sprayed end contacts, a process known to be caused by thermal effects and the effects of electrical discharges. It has also been suggested that electrodynamic effects could contribute to the phenomenon; an experiment was performed to investigate the possibility and the findings confirm that this is indeed the case.
IEEE Power Engineering Review 08/2002; 22(7):64-64.
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ABSTRACT: The benefits of machine condition monitoring have been widely
recognized as superior with respect to other alternative maintenance
approaches. Condition monitoring is an operational strategy for machine
integrity assessment, fault identification and life extension. The
cost-benefit ratio will be reduced in progress owing to the commercial
diagnostic environment availability. This paper presents the
implementation of a diagnostic procedure to detect induction machine
stator faults based on the LabVIEW environment. The diagnosis is
performed by using a suitable neural network, trained by a faulted
machine simulator, that has, as input variables, the negative sequence
current component and the variation of the positive sequence current
component between actual and healthy machine conditions. The statement
of a trigger threshold that discerns between true faults and intrinsic
dissymetry of the machine is discussed as well
Electrotechnical Conference, 1996. MELECON '96., 8th Mediterranean; 06/1996
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ABSTRACT: An automatic procedure to identify online the induction machine
parameters of the steady-state equivalent circuit is presented. The
procedure starts with the acquisition of input current and voltage
instantaneous values and their processing to obtain the following
dataset of variables: current and voltage first harmonic values; their
displacement; and the slip value. The slip value is obtained through the
current spectrum lines due to the rotor slotting. This first step is
automatically iterated if the operating condition changes, in order to
obtain more sets of variables. Different methods identify the parameters
of the equivalent circuit, starting from the available sets of
variables. All this process, configured as a virtual instrument, is
implemented in the LabVIEW environment and can be included in a
diagnostic system to detect machine health conditions, in order to
expand system capabilities
Industrial Electronics, 1995. ISIE '95., Proceedings of the IEEE International Symposium on; 08/1995
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ABSTRACT: Results of research carried out at the Institute of Industrial
Electrical Engineering of the University of Bologna on self-healing
metallized polypropylene (MPP) power capacitors are presented. The aim
of the tests is to characterize the degradation of these capacitors when
employed in automatic power factor correction systems or in power
electronic applications with special reference to the disconnection of
the `sprayed ends' from the electrode-edges, one of the main reasons for
failure of MPP capacitors employed in the above systems. The research is
carried out also in view of the definition of adequate type-test
standards, presently not yet available for this kind of
application
IEEE Transactions on Power Delivery 02/1995; · 1.35 Impact Factor
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ABSTRACT: An example of simulation of a closed loop controlled electric
device that shows the feasibility of simulating the equipment by means
of a general-purpose electronic circuit analysis program is described.
The SPICE program was used because of its well-known facilities for
simulating electronic circuits. A method for extending the SPICE
facilities to simulate the electromechanical energy conversion and the
drive control is reported. The simulation of a switched reluctance motor
drive with closed loop speed control is considered, and the results were
validated by experimental tests executed on an industrial drive
IEEE Transactions on Industry Applications 12/1991; · 1.66 Impact Factor
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ABSTRACT: An explanation of the disconnection of `sprayed ends' from the
electrode edges of metallized polypropylene capacitors is given.
Experimental observations using transparent cells and post-test analyses
of the end-edge contacts show that the disconnection is due to erosion
caused by electric sparks. The sparks are a consequence of the irregular
nature of the contacts and of high intensities of the current flowing
through them. Results of laboratory tests show that the degradation of
the contacts is related to the peak value of the current pulses, in
agreement with the above explanation. In addition, the results confirm
that the degradation is not related to the energy content of the applied
pulses
Properties and Applications of Dielectric Materials, 1991., Proceedings of the 3rd International Conference on; 08/1991
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ABSTRACT: Experiments performed on the end-edge contacts of polypropylene
capacitors to determine whether the thermal effect is the main cause of
their degradation are described. Current pulses with different
wave-shapes but with the same value of the Joule integral were applied
to the contacts, and the degradation levels were ascertained by
measuring the tan δ variation, since degradation of the contacts
results in an increase of the equivalent series resistance of the
capacitor. The results obtained show only a partial dependence of the
degradation level on thermal stress, revealing a contribution from the
electrical and mechanical stresses
IEEE Transactions on Electrical Insulation 03/1991;
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ABSTRACT: One of the most frequent reasons for failure of self-healing
polypropylene capacitors is the detachment of the `sprayed ends' from
the electrode edges. This is typical in power-electronic applications
due to the action of voltage and current pulses which may result in
electrical, thermal, and mechanical stresses. A study is carried out
starting from the hypothesis that, according to previous results
obtained, one of these stresses is dominant and a combined effect is not
to be considered. Assuming that the thermal stress is the most
significant one, several tests have been carried out in order to verify
such hypothesis. The purpose of these tests was to check whether current
pulses with different wave-shapes but with the same value of Joule's
integral lead to the same degradation level of the end-edge contact. The
degradation level is ascertained by measuring the tan δ variation,
since the degradation of the contact results in an increase in the
equivalent series-resistance of the capacitor. Contrary to the starting
assumption, the results obtained show only a partial dependence of the
degradation level on the thermal stress, revealing also a contribution
of the electrical and mechanical stresses
Properties and Applications of Dielectric Materials, 1988. Proceedings., Second International Conference on Properties and Applications of; 10/1988
