1-Phase Auto Transformer

This component models a single-phase auto transformer and is based on the classical modeling approach.

Options are provided so that the user may choose between either a magnetizing branch (linear core), or a current injection routine to model magnetizing characteristics. If desired, the magnetizing branch can be eliminated altogether, leaving the transformer in 'ideal' mode, where all that remains is a series leakage reactance.

Input Parameters

Transformer MVA	REAL	Constant	The apparent power rating of the transformer [MVA]

Base Operation Frequency	REAL	Constant	The base frequency of the electrical system, in which the transformer resides [Hz]

Leakage Reactance	REAL	Constant	The total leakage reactance of transformer. This can be calculated based on short-circuit test results [pu]

No Load Losses	REAL	Constant	The total no-load core losses of the transformer. Winding losses are not to be included in value [pu]

Copper Losses	REAL	Constant	Enter the total copper losses for the transformer. Equivalent winding resistances are calculated based on this entry so that losses are distributed evenly among all the windings. These resistances are then placed in series with the windings [pu]

Ideal Transformer Model	Choice		Select Yes or No. This input must be Yes when modeling core saturation NOTE: 'Ideal' transformer should not be confused with an ideal ratio changer. 'Ideal' here simply means that the magnetizing branch has been eliminated (leakage reactance is still present as well)

On Load Tap Changer	Choice		Select Yes or No. Selecting Yes will enable the on-load tap changer, which requires an external signal input (see On-Load Tap Changer).

Winding Voltage (RMS)

REAL

Constant

The RMS voltage rating of the corresponding winding [kV]

NOTE: See Adjusting Saturation Properties for more details on these inputs

Saturation Enabled	Choice		Select Yes or No to enable or disable the core saturation routine NOTE: Always set the transformer to 'ideal' when enabling saturation. Otherwise, both the magnetizing branch and the saturation routine will both be used.

Air Core Reactance	REAL	Constant	Usually approximately twice the leakage reactance [pu]

Inrush Decay Time Constant	REAL	Constant	The decay time for the transformer inrush current [s]

Knee Voltage	REAL	Constant	The knee point voltage corresponding to the knee point of the saturation curve [pu]

Time to Release Flux Clipping	REAL	Constant	Time interval from start-up in which the model will 'clip' (limit) the calculated flux linkage values. This is simply a modeling 'trick' to prevent instability at start-up [s]

Magnetizing Current	REAL	Constant	The percentage of primary winding current that flows through the transformer magnetizing susceptance. This value can be calculated based on the open-circuit test results. The magnetizing susceptance is calculated based on this value [%]

Name for Winding Current	REAL	Output	Name for the specified winding current [kA]

Name for LV Side Current	REAL	Output	Name for the low voltage side current [kA]

Name for Magnetizing Current (pu)	REAL	Output	Name for the magnetizing current [pu]

Name for Flux Linkage (pu)	REAL	Output	Name for the calculated flux linkage [pu]

1-Phase Auto Transformer

Description

Input Parameters