Transformer Efficiency Model

The output power from the transformer is calculated as:

$$P_\text{trans,out} \left( t \right) = \frac{\sqrt{c_0 + c_1 P_\text{trans,in} \left(t\right)} - 1}{c_2}$$

Where \(c_0\), \(c_1\) and \(c­_2\) are calculated from the transformer parameters \(P_\text{noload}\), \(P_\text{full}\) and \(P_\text{rating}\) as follows (to optimise amount of precalculation possible):

$$c_0 = 1 - \frac{4 P_\text{noload} P_\text{full}}{P_\text{rating}^2}$$

$$c_1 = \frac{4 P_\text{full}}{P_\text{rating}^2}$$

$$c_2 = \frac{2 P_\text{full}}{P_\text{rating}^2}$$

Transformer parameters:

\(P_\text{noload}\) - no-load or core loss [kW] (often given as a % of \(P_\text{rating}\) in inverter documentation)

\(P_\text{full}\) - full-load ohmic (i.e. non-core) loss [kW] (often given as a % of \(P_\text{rating}\) in inverter documentation). (Some data sheets may use the term full-load to refer to the combined core and ohmic losses at rated power, but this is not consistent with IEEE or IEC standards. You may need to be careful which interpretation is used in the data sheet you refer to.)

\(P_\text{rating}\) - output power rating.

Therefore:

$$P_\text{trans,loss} \left( t \right) = P_\text{trans,in} \left( t \right) - P_\text{trans,out}(t)$$