4 wire three phase Wye connected system

[saw]

Hello there,

Can any one tell me what happens if in 4 wire three phase wye connection, one of the phase completely get diconnected?

Thanks

 

[Ship Wreck PE]

If you loose 1 phase in a 3 phase wye system, Strange thing will happen. Three-phase motors will not start, but if they are running, they will continue to run in a single phase mode, which causes high currents and overheating. If you were to loose the neutral conductor, bad things will happen.. Devices connected between a phase conductor and the neutral, will now be connected between two phase conductors in series with other devices, and the device with the highest resistance will get an unwelcome surprise.

 

[user 26087]

^^^ This is very true. We constantly lose a phase from the utility at work and one of the mechanical rooms is near my cubicle. I can always tell when we lose the phase due to the noise the motor makes. We will go and shut down the unit until the utility notifies us we are good. Also my in-laws lost their neutral from the utility side and it caused all of their electronics, and some appliances to get fried plus a small fire had started.

 

[saw]

Thanks a lot for the respond.

 

[Peele1]

We had a 3-phase system here, though nobody knew it was 3-phase. When they turned it off, the whole room powered off. Turns out it, the room was very unbalanced, and one leg had about 125% on it, and one leg only about 25%, and the other was about 75%, so this single 3-phase device was back feeding and balancing everything out. They had to re-wire a lot of stuff to re-balance just to turn off the one 3-phase device.

I don't know if it was Y or delta connected, most likely Y.