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Εργαστήριο - Ανακοινώσεις
Quasimodo Ver.4.0 Snubber Test
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<blockquote data-quote="lemon" data-source="post: 1057764039" data-attributes="member: 16016"><p>Ναι δυστυχώς το νήμα το κάνανε μεγάλο, άνευ λόγου και ουσίας. Συνεχείς μετρήσεις επί των ίδιων θεμάτων και συνεχής θεωρια-τυπολατρεία με υπολογισμούς!</p><p></p><p>Προσπαθείς να πάρεις την ουσία, αλλά θέλει πολύ μελέτη.</p><p></p><p>Κάπου θυμάμαι ότι ο Mark, είχε στηρίξει την άποψή του ότι δεν είναι απαραίτητο να μετρήσεις <em>In Situ</em>. Δεν είναι τυχαίο, ότι το παραμετροποίησε για μέτρηση εκτός λειτουργίας.</p><p></p><p>Τα αγγλικά σου είναι άψογα μπροστά στα δικά μου. Σου παραθέτω μια απάντηση μέλους (post 885) κάνοντας σε μερικά σημεία μορφοποίηση έντονου ή υπογραμμισμένου.</p><p></p><p>"The purpose of Quasimodo is to provide wide-band excitation to a circuit comprising the leakage inductance of the transformer, <strong><u>whatever capacitance is present (parasitic and/or Cx-added)</u></strong>, and some small resistance of the secondary winding being tested. The excitation energy comes from the steep falling edge in the secondary current when the output MOSFET starts conducting in each pulse.</p><p>Depending upon the configuration, an oscillatory circuit is characterised by one or more so-called natural frequencies, sometimes referred to as modes, and will oscillate at these frequencies if there is enough excitation energy. We then speak of resonance(s).</p><p>Assuming that there is only a single natural frequency, we see a sinusoidal pattern on the oscilloscope, generally decaying with time due to the natural damping in the circuit, provided by e.g. winding resistance.</p><p>So the key facts are that there are a circuit that can oscillate if excited and enough excitation energy at the circuit's natural frequency.</p><p><u>Going over to the same transformer in a PSU with rectifiers</u>, whenever a rectifier diode stops conducting there will be a more or less steep falling edge in the secondary voltage, which in turn may provide excitation energy for the resonance to happen. Without a snubber, this oscillation is clearly visible on the scope in most cases; and by connecting an appropriate Rs-Cs combination parallel to the secondary winding the oscillation can be quenched. Note that the PSU must be loaded for this test to work, but not necessarily with the full load. Several screenshots obtained in such testing can be seen in Post #735.</p><p>So from the standpoint of physics, both methods satisfy the purpose of the procedure, i.e. determining the snubber configuration that prevents the parasitic oscillations from taking place. However, due to the different testing conditions, they may not produce the same Rs value.</p><p><strong>I routinely use Quasimodo to determine an optimal snubber for every incoming transformer, but I also check for ringing in the PSU built with this transformer. In my experience, oscillations in situ can usually be quenched with a higher Rs value than determined with Quasimodo, which results in less dissipation.</strong>"</p><p></p><p>Τέλος είναι γνωστό σε όλους ότι οι Soft Recovery Diodes δίνουν λιγότερο κωδωνισμό στο M/T, για του λόγου το αληθές σε όσους ενδιαφέρονται... <a href="https://linearaudio.net/article-detail/2242" target="_blank">https://linearaudio.net/article-detail/2242</a></p><p>Αναφέρει 10Χ-20Χ λιγότερο κωδωνισμό από τις απλές. Το άρθρο αυτό είναι του κατασκευστή του Quasimodo, αλλά δυστυχώς για να το διαβάσεις όλο θέλει ένα μικρό ποσό.</p><p>[h=1][/h]</p></blockquote><p></p>
[QUOTE="lemon, post: 1057764039, member: 16016"] Ναι δυστυχώς το νήμα το κάνανε μεγάλο, άνευ λόγου και ουσίας. Συνεχείς μετρήσεις επί των ίδιων θεμάτων και συνεχής θεωρια-τυπολατρεία με υπολογισμούς! Προσπαθείς να πάρεις την ουσία, αλλά θέλει πολύ μελέτη. Κάπου θυμάμαι ότι ο Mark, είχε στηρίξει την άποψή του ότι δεν είναι απαραίτητο να μετρήσεις [I]In Situ[/I]. Δεν είναι τυχαίο, ότι το παραμετροποίησε για μέτρηση εκτός λειτουργίας. Τα αγγλικά σου είναι άψογα μπροστά στα δικά μου. Σου παραθέτω μια απάντηση μέλους (post 885) κάνοντας σε μερικά σημεία μορφοποίηση έντονου ή υπογραμμισμένου. "The purpose of Quasimodo is to provide wide-band excitation to a circuit comprising the leakage inductance of the transformer, [B][U]whatever capacitance is present (parasitic and/or Cx-added)[/U][/B], and some small resistance of the secondary winding being tested. The excitation energy comes from the steep falling edge in the secondary current when the output MOSFET starts conducting in each pulse. Depending upon the configuration, an oscillatory circuit is characterised by one or more so-called natural frequencies, sometimes referred to as modes, and will oscillate at these frequencies if there is enough excitation energy. We then speak of resonance(s). Assuming that there is only a single natural frequency, we see a sinusoidal pattern on the oscilloscope, generally decaying with time due to the natural damping in the circuit, provided by e.g. winding resistance. So the key facts are that there are a circuit that can oscillate if excited and enough excitation energy at the circuit's natural frequency. [U]Going over to the same transformer in a PSU with rectifiers[/U], whenever a rectifier diode stops conducting there will be a more or less steep falling edge in the secondary voltage, which in turn may provide excitation energy for the resonance to happen. Without a snubber, this oscillation is clearly visible on the scope in most cases; and by connecting an appropriate Rs-Cs combination parallel to the secondary winding the oscillation can be quenched. Note that the PSU must be loaded for this test to work, but not necessarily with the full load. Several screenshots obtained in such testing can be seen in Post #735. So from the standpoint of physics, both methods satisfy the purpose of the procedure, i.e. determining the snubber configuration that prevents the parasitic oscillations from taking place. However, due to the different testing conditions, they may not produce the same Rs value. [B]I routinely use Quasimodo to determine an optimal snubber for every incoming transformer, but I also check for ringing in the PSU built with this transformer. In my experience, oscillations in situ can usually be quenched with a higher Rs value than determined with Quasimodo, which results in less dissipation.[/B]" Τέλος είναι γνωστό σε όλους ότι οι Soft Recovery Diodes δίνουν λιγότερο κωδωνισμό στο M/T, για του λόγου το αληθές σε όσους ενδιαφέρονται... [url]https://linearaudio.net/article-detail/2242[/url] Αναφέρει 10Χ-20Χ λιγότερο κωδωνισμό από τις απλές. Το άρθρο αυτό είναι του κατασκευστή του Quasimodo, αλλά δυστυχώς για να το διαβάσεις όλο θέλει ένα μικρό ποσό. [h=1][/h] [/QUOTE]
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Quasimodo Ver.4.0 Snubber Test
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