Blown neutral line on 3 Phase System

Discussion in 'General Electronics Chat' started by olivepearl, May 17, 2009.

  1. olivepearl

    Thread Starter New Member

    May 17, 2009
    I have a system that requires 3 phase power. When connecting a cable that supplies 3 phase power to the system the neutral line arced, smoked and melted causing destruction of system. I do not expect anyone to tell me the exact cause but what are the general causes of 3 phase neutral line to suddenly carry so much power?
    Last edited: May 17, 2009
  2. Cav1.6E-19

    New Member

    May 17, 2009
    Three phase systems don't use a neutral.

    What exactly do you mean by "three phase system"?
    Is this a single piece of equipment which uses three phase power, or is it a collection of single and multiple phase equipment wired into a three phase system?

    Senior Member

    May 15, 2009
    Please try to add some sort of diagram and a bit more discription
  4. DonQ

    Active Member

    May 6, 2009
    Star (or Wye) certainly do have a neutral. If the loads on the 3-phases are balanced, then there will ideally be no net current in the neutral, and it is often sized smaller than the hot wires. Star systems are much less used than Delta. Is this what you are using?

    If, for example, one of the phases of a 3-phase motor is open (or shorted!), then the current in the neutral can be huge. Even an improperly rewound motor can cause problems in this regard.

    There are protection devices that can detect phase imbalance and open the circuit much quicker than a breaker or motor-starter. Might be worth a look.

    Delta systems can be wired with one leg grounded, but I would not call this wire a neutral in this case, in that it carries the full load current.
  5. Jsw123

    Active Member

    Jun 20, 2009
    Possibly you have a lot of line to neutral nonlinear (inductive or capacitive) loads on the phases. Single phase motor loads are a common example. This causes harmonic neutral currents. (neutral currents may add to 1.73 x phase current)

    Does this load supply a dedicated piece of 3 phase equipment or an electrical panel?