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Transformer
Last Post 12 Jun 2012 10:07 AM by Aqua_Azul. 2 Replies.
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Aqua_Azul
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Posts:2

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06 Jun 2012 10:02 AM
    I wanted to see if I could get some kind of input on this issue at hand. I have two Electrical control panel which powers two UV Systems. The incoming Power is 120 VAC with each Panel on its own breaker of 20 AMPS. The transformer, which was provided by others, has a Primary Voltage of 480 and has three leads of 120 VAC on the Secondary. Recently we had swapped out the ballast which caused the Breakers to trip due to Higher Amp draw from the ballast. So we reverted to the old ballast that had been initially on the panel. Two weeks later The transformer blew one leg on the Secondary Voltage. So what my question is if the panels are protected by, two things, a fuse in the Panel and a Circuit Breaker, how could the UV Panel have caused the transformer to burn out if it's protected?
    jwd217
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    06 Jun 2012 12:42 PM
    You state that the incoming power is 120 VAC but the transformer primary is 480 with secondaries of 120. So if you really have 120V on the 480 primary you will only get 30 VAC on the output. Which means that the transformer is 4:1 voltage ratio and a 1:4 current ratio. So if the primary is protected by a 20 amp breaker, the secondaries would have to draw 80 amps to trip the breaker. The transformer probably is not rated for that much current. So it could be overloaded and still draw less current than the 20 amp breaker would trip at. To properly protect the transfomer, it needs to be connected to a smaller breaker. The proper size depends on the transformer current rating. If the load needs more current than the transformer is rated for, then you need a bigger transformer.
    Aqua_Azul
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    12 Jun 2012 10:07 AM
    Well thank you for the insight on this issue I will present this to my other engineers in house to see if we can come up with a solution.
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