30 amps imbalance

[Frank DuVal]

Actually, 70 AMPS!

QO170

Editing to try and remove need to download page to read..... hold on....

 

[Frank DuVal]

 

[Frank DuVal]

Why would a transformer care if only one side of a center tap was fully loaded? The power rating would still be higher than the load on it. A center tap winding is just two secondary windings that happen to be tied together inside the transformer.

A transformer with several secondary windings would not care if some of the windings are unused.

The load is still single phase on the primary side, typically one phase to neutral, although some power companies use two phases and no neutral for the primary winding (have not seen those in these parts in 50 years!)

 

[wwhitney]

Why would a transformer care if only one side of a center tap was fully loaded?

That's true for a single phase secondary, but with a center-tapped delta secondary, imbalance can lead to transformer overload even when all the load currents are less than the transformer rated current, due to additional circulating current. See https://forums.mikeholt.com/threads...-of-3-phase-transformer.2582774/#post-2941681 for the details.

Cheers, Wayne

 

[OldBroadcastTech]

"That's true for a single phase secondary,"

which is where this discussion started.......no doubt there are 'concerns' that "with a center-tapped delta secondary, imbalance can lead to transformer overload " but we have strayed from the original question of whether or not 30 amps of neutral current is necessarily a Bad Thing

 

[ptonsparky]

IMO you would need to work at getting a sustained imbalance of 30 amps.

 

[Elect117]

"That's true for a single phase secondary,"

which is where this discussion started.......no doubt there are 'concerns' that "with a center-tapped delta secondary, imbalance can lead to transformer overload " but we have strayed from the original question of whether or not 30 amps of neutral current is necessarily a Bad Thing

As long as everything is done properly. No.

Neutral current is to be understood in context and reduced when able. Imbalance is not ideal.

Most replies are including context. For example, is the sky blue? Well, yes. But not always. Like at dusk or dawn. Or if it is cloudy. etc.