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#1 |
diyAudio Member
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I have a pair of Electronic R-core 300VA 230V primary 2x 21v secondary that I plan use in Peter Daniels LM3875 monoblocks.
I understand for larger toroids it is a good idea to use inrush/soft start protection. Does the same apply for R-core transformers? I have Sjostrom SST03 soft start modules that I could use but if not necessary would hold them for another project. Thanks |
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#2 |
diyAudio Member
Join Date: Oct 2004
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My understanding is that such a circuit would be needed when a large bank of capacitors were to put a strain on the rectifier array upon startup. A transformer won’t produce enough heat in the short burst at power on to be a problem in most cases.
I have large amps with no means of soft starting, and are working fine after some 40 years. A speaker protection circuit with a relay to eliminate the possibility of a blast of DC at startup is a great thing. |
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#3 |
diyAudio Member
Join Date: Oct 2011
Location: Kyiv
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#4 |
diyAudio Member
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#5 | |
diyAudio Member
Join Date: Oct 2011
Location: Kyiv
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Quote:
I think it is always a good idea to use a soft-start (at least small value NTC) with any transformer. You may test the exact inrush current value with an oscilloscope (or any fast AC ammeter). Or, if you have a lot of fuses of different ratings then you may test it with a go through a few different fuses (from a small value to large or vice versa). My simple estimated rule is this: if a fuse rated as the twice as rated load doesn't burn then it is ok. If you have to use a much higher fuse value then use some soft-start. |
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#6 |
diyAudio Member
Join Date: Feb 2006
Location: Athens
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Sthcoaster, Put a NTC resistor, e.g. CL 60, in series with transformer primary.
That’s all.
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Esoteric K-03, Viva Solista MK3, Sonus Faber Amati Aniversario, First One L, Salas DCG3, PeeCeeBee V4H. |
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Thread | Thread Starter | Forum | Replies | Last Post |
testing without inrush protection | ultrachrome | Power Supplies | 16 | 6th December 2009 12:59 AM |
Inrush current protection for big toroidal transf ? | nina | Chip Amps | 3 | 19th April 2006 04:40 PM |
Thermistor or relay for inrush protection | Kees | Solid State | 17 | 14th April 2005 06:14 AM |
Aleph 5 inrush current protection | vossie | Pass Labs | 33 | 6th December 2002 03:36 PM |
Inrush protection failures. | Peter Daniel | Pass Labs | 32 | 27th September 2002 12:01 PM |
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