Single phase two winding variable ratio transformer

This section describes the single phase two winding variable ratio transformer component

The single phase two winding variable ratio transformer component models two coupled windings on the same core. The magnetization inductance Lm can be modeled as linear or with saturation. Core losses are modeled as a shunt resistance Rm. Both Lm and Rm are modeled on the primary side of the transformer. It is possible to neglect Lm and Rm by selecting Lm/Rm neglected in the Core model property. For more information on the core model, please refer to Core model.

When the Core model property is set to Lm/Rm neglected, the primary inductance L1 may be degenerated. If it is desired to preserve L1, a snubber can be defined under the stability tab to provide an alternative current path at the transformer primary. Alternatively, the Refer L1 to secondary checkbox provides the option to refer the effects of inductance L1 to the secondary side of the transformer. If this option is selected, inductances L1 and L2 are replaced with a single variable inductor L2_var on the transformer secondary.

The schematic symbol and input parameters for the single phase two winding variable ratio transformer component are given in Table 1.

Table 1. The single phase two winding variable ratio transformer component
component component dialog window component parameters

Single phase two winding variable ratio transformer
  • Input parameters option – SI/p.u.
  • Nominal Power of the transformer in VA (Sn)
  • Nominal frequency in Hz (fn)
  • Nominal voltage of the primary winding (n1)
  • Nominal voltage of the secondary winding (n2)
  • Leakage inductance of the primary winding (L1)
  • Initial current on primary side (I1)
  • Leakage inductance of the secondary winding (L2)
  • Initial current on secondary side (I2)
  • Core model - Linear, Non-Linear, Rm/Lm neglected
  • Magnetization Inductance (Lm)
  • Primary winding resistance (R1)
  • Secondary winding resistance (R2)
  • Equivalent resistance representing the iron core losses (Rm)
  • Import from PU button

  • Enable signal output - passes individual phase voltage and current values to a signal processing output port.
  • Execution rate - defines the execution rate of measurement and signal processing components.
  • Use RMS - passes RMS values for measured voltages and currents.
  • Snubber Type - adds a snubber to the current source side of the embedded single phase transformers.
  • Resistance - sets the series resistance value of the snubber if Snubber Type is set to R or RC.
  • Capacitance - sets the series capacitance value of the snubber if Snubber Type is set to RC

A schematic block diagram of the single phase two winding transformer block with the corresponding component arrangement and naming is shown in Figure 1.

Figure 1. The schematic block diagram of a single phase two winding variable ratio transformer with corresponding components naming

Analog output signals from Enable signal output

When the Enable signal output checkbox is checked, a vector of internal variables of the transformer is passed to the output port out. These values are the primary and secondary voltages and currents for the individual single phase transformers. Each of the analog output signals is instantaneous in nature by default. If the Use RMS option is checked, the RMS values of each output will be returned instead.
Analog output variable nameDescription
VprmPrimary voltage of the transformer 
IprmPrimary current of the transformer 
VsecSecondary voltage of the transformer 
IsecSecondary current of the transformer