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  1. #11
    Thanks, guys. I have just wired the AC to DC transformer bits together for the first time and connected it to the mains. I have not yet used a 'delay on' timer relay and just wired an NTC thermistor on the live between mains in and the primary winding. On first switch on nothing dramatic happened and I am getting 53 volts at the DC output which is close to what I wanted. I was surprised that the thermistor did not get hot like I thought they were supposed to. Could this be because there is no load on the DC output? Similarly the bridge rectifier does not seem hot or even warm. Is this normal? The thermistor is a SL15 2R507 that Airlink transformers recommend for toroidals up to 1kVA
    Regards ...Chris
    Last edited by chillybo; 11-07-2019 at 05:00 PM.

  2. #12
    Doddy's Avatar
    Lives in Preston, United Kingdom. Last Activity: 3 Hours Ago Has been a member for 5-6 years. Has a total post count of 534. Received thanks 86 times, giving thanks to others 20 times.
    Quote Originally Posted by chillybo View Post
    Similarly the bridge rectifier does not seem hot or even warm. Is this normal? The thermistor is a SL15 2R507 that Airlink transformers recommend for toroidals up to 1kVA
    Regards ...Chris
    Keep an eye on it under load, but there's many toroidal running with just NTCs - that's what they're designed for. If it works - you've saved yourself 40.

    (Mine has just an NTC on a 800VA transformer)

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  4. #13
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    Just need to create a load for it now so I need to know what are the best stepper drivers for my set up. It will probably be better to start a new thread for this.

    Regards ...Chris

  5. #14
    Muzzer's Avatar
    Lives in Lytham St. Annes, United Kingdom. Last Activity: 5 Hours Ago Has been a member for 1-2 years. Has a total post count of 39. Received thanks 12 times, giving thanks to others 2 times.
    The second one looks like a bit of a home project, TBH. The first (German) one looks pretty sensible, containing an NTC, timer relay and overtemp protection.

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  7. #15
    In post 10 ,the second link for the
    "Soft-start, inrush current limiter for toroidal transformers-assembled, tested"

    reminded me of project 39 from Elliott Sound Products
    Soft-Start Circuit For Power Amps
    http://sound.whsites.net/project39.htm

    project list
    http://sound.whsites.net/p-list.htm

    John

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