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The paper presents the results of an experimental work to examine the times-to-failure of various types of turn insulations used in form-wound stator coils. A unipolar PWM waveform with a peak of 12 kV, rise time of approximately 270 ns and switching frequency of 3 kHz is used for aging. The types of insulations studied include enamel, Daglas®, mica tape with polyester film, and enamel plus mica glass tape. The time-tofailure data are analyzed using two-parameter Weibull statistics. The breakdowns are examined microscopically providing information as to the probable reason for the failures. The role of each type of insulation; enamel, Daglas® and mica polyester film tapes, and their dimensions are discussed to explain the times-tofailure under PWM aging.

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Several investigations show that there is an effective process to break a microorganism's membrane using the pulsed electric field (PEF) in order to pasteurize liquid foods. Such pulsed electric fields are produced by high voltage, high peak current and fast rise-time pulses applied to a chamber with liquid passing through it. Due to the nature of the short pulses the processes is non thermal; hence, it helps to save the nutritional values of the treated food as well as its taste. Thus PEF treatment is considered as a good alternative to the conventional pasteurization treatments that are thermal processes.The aim of this work is to study the effect of design parameters such as switch type, gate drive circuit, and circuit configuration on the output voltage rise and fall times using a newly developed solid state pulsed generator. The paper presents the results obtained from treating liquid samples whose electrical conductivities fall in the range of a variety of liquid foods, using a variable 0-6 kV, with 3f.1s flat-top pulses; and rise-time of 70-1000ns. The peak current rating of the pulse generator 1500A, can sustain the heavy loading due to the high conductivities of the treated samples.