Secondary Waveform Research Articles

A parallel resonant converter with postregulators

A parallel resonant power converter (PRC) with postregulator(s) power synchronized to the primary switching frequency is investigated for discontinuous-conduction mode operation. It is analyzed with a magnetic amplifier, which blocks the rising edge of the secondary voltage, and with a synchronized buck regulator, which blocks part of the trailing edge of the secondary voltage waveform under the steady-state conditions. As a result, it has been shown that magnetic amplifiers are not suitable for resonant mode power converters, since the step change of the load from low to high during the same switching period as the primary makes the operating conditions worse. However, postregulators that block the trailing edge of the secondary voltage waveform do not adversely affect the operating conditions of PRC and work satisfactorily. As an alternative, a PRC with a magnetic postregulator is presented. An offline 150 W 250 kHz PRC is designed with a magnetic postregulator for a personal computer application, and experimental waveforms are included.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Method of reducing the adaption time in the cancellation of repetitive vibration

A method of reducing the adaption time needed to adapt a synthetically generated secondary waveform so that it nulls a primary repetitive waveform (e.g. noise) from a source (1) of vibration, the secondary waveform generation (5) being synchronized by the source (1). The clarity and/or the amplitude of at least a part of the signal resulting from interaction between the primary and secondary waveforms is sensed (6) and used (7, 8) to reshape the secondary waveform. The invention finds application in the cancelling of repetitive vibrations (e.g. in quietening the driving cab of a vehicle).

Parametric Acoustic Waveform Generation from Spherical Primary Fields

Parametric acoustic secondary signals which are generated largely within the nearfield of the primary sound beam exhibit a waveform proportional to ∂2F2/∂t2, where F is the envelope of the primary waveform and t is the time. However, the secondary waveform can be expected to tend toward ∂F2/∂t as more of the parametric generation occurs in the farfield of the primary beam. In an experiment conducted at the Millstone Quarry facility of the Naval Underwater Systems Center, the latter waveform has been produced by the modulation of a 330-kHz primary pulse from a 1.5-in.-diam underwater sound projector. [This work was supported in part by the National Science Foundation.]

The secondary circuits of synchronous induction motors

The use of synchronous induction motors has steadily increased in the last 15 years, and much information about them is now contained piecemeal in various papers. No critical account of the various types of secondary circuit and of the ways of exciting them is yet available, however, and in the first part of this paper the author considers these systematically. The characteristics desirable are first elucidated, and each winding is then considered in the light of these characteristics. Their properties are finally summarized in tabular form.The second part of the paper describes experiments by the author on the load reactance of synchronous induction motors. The relation between load and synchronous reactance for a machine with a barrel rotor is established practically, as is also the dependence of both these quantities on the secondary wave form. A correction for “magnetic backlash” is introduced.The third part of the paper deals shortly with parasitic currents in secondary circuits, with oscillograms of these currents.The appendices give mathematical results for secondary wave forms, ratings, starting torques and exciting currents. These results serve as standards with which actual results can be compared.