On a Open Delta connection, voltage fluctuation 1

[donsoy]

On a delta connection and one of the legs fails and creates an open delta. What causes the voltage fluctuation?

Is the fluctuation of voltage caused by the variants of the load (ie: load dependent?).

 

[jbartos]

Comment: Harmonics can propagate through the open delta and cause fluctuations, if the input power quality is inferior.

 

[alehman]

If the load is unbalanced, there will be a significant voltage change. Also, the available transformer capacity will be reduced to 58% of the 3-phase capacity.

 

[jbartos]

Comment: The load behavior and symmetry should not be overlooked.

 

[busbar]

On its own, a delta winding can devolve into open delta if the continuity of one coil within the delta is interrupted. Both are three-phase, given the limitation alehman pointed out. If instead one external connection to a pair of coils is opened, then what remains is a pair of series coils, in parallel with a full coil, with merely two external connections. That is a single-phase condition.

 

[jbartos]

Comment on the original posting marked ///\\
On a delta connection and one of the legs fails and creates an open delta. What causes the voltage fluctuation?
///Beside mentioned harmonics in my above posting; the open delta connection has the higher transformer current flowing through the transformer windings for the same rated load. This causes the higher voltage drop across the transformer, and the transformer overload. Therefore, the open delta transformer load should be decreased to sqrt3 x kVArated x (1/3) = .577 x kVArated.\\Is the fluctuation of voltage caused by the variants of the load (ie: load dependent?).
///Yes. The transformer voltage fluctuation is caused by the open delta connection. It is load dependent. The higher load, the higher voltage asymmetry. If the load is nonlinear, all harmonics will propagate through the open delta connection.\\