230 to 120 transformer help

Discussion in 'The Projects Forum' started by tonyromano1544, Apr 24, 2012.

  1. tonyromano1544

    Thread Starter New Member

    Feb 13, 2012
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    The theory of two hot connections has always been a little confusing for me. I am trying to get a 115v little pump to run off of 230v.

    I have a 240vac connection on a piece of medical equipment. There is a little pump on there that runs on 220v @.11amps. The pump that I am talking about is no longer supported at 220vac they only make it in 115v now.

    I bought this transformer http://www.alliedelec.com/search/productdetail.aspx?SKU=70009008 and I can not get it to work. I hooked black and red to the two pin connector which is 240vac. And I hooked Black and white to my meter and BOOM tripped the breaker. Will this transformer work? The connector is 120v on each side relative to ground (the machine Chassis) it is a 2 pin connector. The pump is just a little 115v pump with two wires.


    PLEASE help!
     
  2. MrChips

    Moderator

    Oct 2, 2009
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    What kind of meter did you use? What range was the meter set at?
    Sounds like your meter or meter leads were set for 10A or 20A range.
    You should make sure your meter is set for 500VAC or 1000VAC and the leads in the correct sockets.
     
  3. tonyromano1544

    Thread Starter New Member

    Feb 13, 2012
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  4. cmwilson7

    New Member

    Apr 24, 2012
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    Did you have all of this wired up, i.e. machine to transformer and transformer to meter and then apply power and trip the breaker? Or, did you just touch the meter leads to the transformer and then trip the breaker?


    Also, Although the pump will still work at 50Hz. A transformer is not going to convert the frequency to 60Hz either. It will run slower, hotter, draw more current, etc.
     
  5. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    The connection is correct. The transformer should also be able to supply the current to the pump, it has a 50VA rating...
    Are you sure about the 115V pump's current rating?
     
  6. tonyromano1544

    Thread Starter New Member

    Feb 13, 2012
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    I am positive about the 115v @ .11amp rating, and the line and the motor are 60hz. I know that this transformer will not change that. Does anyone know if an autotransformer (which is what this is) causes problems with no load? The meter was already in the circuit when I turned it on. And the main instantly tripped. So there was basically no load due to the high impedance of the meter. (btw after disconnecting the transformer it didn't trip again) Thanks for the help everyone.
     
  7. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    No, that's not normal.

    What is the circuit breaker rating? (peak current) Can you tell us the model number/manufacturer?

    Above you were saying 220V/0.11A. Now you are saying 115V/0.11A. Since this is a new model with a lower voltage rating it should actually draw more current. Do you have it's spec sheet?
     
  8. cmwilson7

    New Member

    Apr 24, 2012
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    Asked about the 60Hz thing because I didn't know where you were located.... You are in the U.S.?

    I have a feeling that the chasis of the autotransformer is tied to the black wire internally and the hot leg of your connection from the machine was shorted to ground through the case of the transformer/machine. Was the transformer touching the case of the machine? On the plug coming from the machine that is 230V.....take your meter set to AC and read the voltage between one of the pins and the chasis? Should be 120V. You could connect this way. Or, since you have an autotransformer and I bet that the black wire is connected to the chasis of the transformer, you would have to isolate the chasis of the transfomer and pump to be able to use it. (Check continuity between the black wire of the transformer and the chasis of the transformer...without it powered, of course)
     
  9. MrChips

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    That doesn't sound right to have a short from the winding to the laminate.
    If so, the transformer is defective.
     
  10. cmwilson7

    New Member

    Apr 24, 2012
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    I bet it is made this way! Intended to be used line to neutral on 400V/230V maybe?
     
  11. GetDeviceInfo

    Senior Member

    Jun 7, 2009
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  12. tonyromano1544

    Thread Starter New Member

    Feb 13, 2012
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    I was checking output voltage before inserting the motor, so the AC setting was set on the Fluke. The rating of the motor doesn't really matter yet because it isn't even in the circuit. I just showed the amp rating because it is a small transformer and I knew someone would comment on that. I will try again today. What I am thinking is that transformer is designed for 230v with a neutral line instead of the two hot 115 lines like I have. It is an auto transformer (link below) so it is one coil and not two so technically it is shorted.

    http://en.wikipedia.org/wiki/Autotransformer (I know it is wikipedia but it is the most straight forward description)

    Thanks guys. Will let you know.
     
  13. GetDeviceInfo

    Senior Member

    Jun 7, 2009
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    you probably don't want to be bothered, but it seems like a miss application. How could one justify non isolation in the medical industry?
     
    shortbus likes this.
  14. MrChips

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    A properly working meter set to measure voltage would present a high impedance and would not cause the circuit breaker to trip.

    If the meter was the reason the breaker tripped then either the leads and meter were set to measure 10A or the meter is faulty.
     
  15. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    I totally agree with this! If this is in a hospital or nursing home I can see a law suit in the OPs future!
     
  16. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    He had a 230VAC pump in there before, so apparently no transformer at all...

    If it is designed for 230VAC then you should be able to connect 230VAC to it without tripping circuit breakers. It doesn't matter how you call the terminals.

    I would check if there are no shorts from the terminals to the core.

    You could confirm that the transformer is working by connecting the 115V terminals to the grid and measuring if you get 230V out of it.
     
  17. cmwilson7

    New Member

    Apr 24, 2012
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    Get rid of the transformer and wire line to neutral. If the pump switches on and off with the 230v, then use one leg off the switch (plug that feeds the 230v) and neutral.
     
  18. tonyromano1544

    Thread Starter New Member

    Feb 13, 2012
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    Ok guys here is what it was... My transformer was an autotransformer which is a single coil with a tap, basically an inductor. Since the only load I had on it was my meter the current had nowhere to go and it tripped. When I hooked one a light bulb and tested it worked. Moral of the story, if an autotransformer does not have a (big enough) load it will basically be a short and it won't work.
     
  19. praondevou

    AAC Fanatic!

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    Strange enough. I worked with several autotransformers (bigger ones though) , and never experienced this problem.

    An inductor on AC is not a short.

    Glad you solved the problem.
     
  20. MrChips

    Moderator

    Oct 2, 2009
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    No, that should not happen. Something is still wrong.
     
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