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  1. #1
    Join Date
    Jun 2007
    Posts
    36

    Slowstart for transformer?

    I have a transformer with primary 220V and secondary 0-260V 16A
    It is as of now fitted with a electronic fuse that is too quick so it blows every time it is turned on and you have to "triple click" to get it to work. It also blows the main fuse sometimes.

    I was thinking of putting a bulb or resistor in series to energize the coil before putting it on full mains. Is this a good way to solve the problem?

    Or is there some other simple circuit that will prevent the high current spike when turned on?

  2. #2
    Join Date
    Dec 2003
    Posts
    24223
    Make sure you use a slow-blow fuse, if you are using a large DC supply on the secondary, you could have a switch that controlled the DC side after the initial inrush on the primary.
    Also with the VA Txfr rating you are using, the primary circuit should be rated at least 20amps.
    There a are negative temparature thermisters but it would be rather large for your case.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  3. #3
    Join Date
    Jun 2007
    Posts
    36
    10A 230V Mains. I will never get close to draw full power for it anyway. Only for testing things with etc.
    I turn it on with no load.
    I am thinking of using it to control the speed of motors etc but I need to have it starting reliably first.
    I will go out to the garage and get some more info on it when I get time. It's a lot of things in front of it.
    I'm not sure what "VA Txfr" is.
    Did I mention it is heavy? I can post some pictures later if it helps.
    I could replace the fuse with a normal slow fuse and a separate switch but I feel that it will still a problem when turning it on. It could have been an old fuse that blew and it will be fine runnig it as is. (with new fuse and switch) But I still think it might be better to give it a slow start as I hate low spikes on the mains.

  4. #4
    Join Date
    Dec 2003
    Posts
    24223
    Quote Originally Posted by David_Web View Post
    But I still think it might be better to give it a slow start as I hate low spikes on the mains.
    If the secondary is in fact 16a at 260v then it is roughly 4kva!

    As Crocodile Dundee said that's not a spike, This is a SPike
    Attached Thumbnails Attached Thumbnails SPIKE.jpg  
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  5. #5
    Join Date
    Jun 2007
    Posts
    36
    IBM had a server that required a very slow fuse.
    It draw in exess of 200A when turned on. Ether 220V 1 phase or 2 phase 360V. Can't remember.

    Anyway I will change fuse and awitch to run it as is. If it becomes a problem in the future I will see to it then. Thanks.

  6. #6
    Join Date
    Dec 2003
    Posts
    218
    A slow blow or antisurge fuse on your supply will solve the local problem.

    You can also get different breakers for your main fuse box. I forget what they are called .. I think it is a D-type or F-type breaker which is immune to high current draw at startup.

    I ended up buying 4 x 1kva transformers and I use timer relays to sequence the start up. Avoids all the problems of drawing too much in one go.
    Dom
    http://www.ukrobotics.com/projects

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