Current Vs Power Transformer

Discussion in 'General Electronics Chat' started by spaminator, Dec 12, 2004.

  1. spaminator

    Thread Starter New Member

    Oct 1, 2004

    I've been looking around the internet and have so far been unsuccessful in finding info on the differences between current and power transformers (3-phase).
    My guess is that a current transformer steps-up current by having less secondary windings... and a power transformer steps-up voltage by increasing the number of secondary windings when compared to the primary windings.

    This explanation seems a little too simple!

    Another thing i was wondering about, is that a superior of mine was telling me that when dealing with current transformers, it's important not to short circuit the terminals (or open circuit them, i can't remember which one)... when i asked why this was the case, he said he wasn't sure, but that it caused arcing between the terminals.

    Would there be a similar issue to consider in power transformers?

    Does this make any sense!? I would really appreciate a response.
    Thanks for your help
  2. spaminator

    Thread Starter New Member

    Oct 1, 2004
    I am replying to myself as i think i've answered my questions by checking this site out more thoroughly...
    i found the section on CT's, and how they shouldn't be operated with an open-circuited secondary winding, because they are wound as as voltage step-up transformers. So apart from safety issues, i guess this is what could cause arcing?
    i've also come to conclude that the power transformer i wanted info on, is actually is 'potential' transformer. my colleagues told me it was a power transformer as it is listed PT on the diagram, but being a potential transformer would make much more sense.

    I'm still wondering though, if you operated a PT with a short circuit, like the one described in the "Special transformers and applications" part of this website, would we just blow up the transformer due to excessive current which would overheat it?

  3. Xray

    Well-Known Member

    Nov 21, 2004

    I believe you are confused about names. The term "power transformer" is simply a transformer that is use to convert the AC Mains voltage to some other voltage that is useful for the circuit being powered. Some power transformers are step-up and some are step-down. Some power transformers include multiples of both functions. A current transformer (CT) is used to monitor the current in a circuit, and at the same time having minimal effect on the circuit. For example, the "primary" winding of a CT may consist of only one turn, or a half turn, of wire. The "secondary" winding has enough windings to provide a voltage to the device that is monitoring the current (usually a meter). So, a CT is a current-to-voltage converter. As far as shorting or opening the windings, of course a power transformer would overheat and burn out. A CT "may" burn out depending on the type of transformer, and the amount of current that flows through the short circuit.

    Hope this helps.