In 2003, the e-Rated Transformer Corporation developed a sophisticated computer program that calculates transformer excitation and impedance losses under linear or any nonlinear load condition, annual savings, payback, return-on-investment and environmental benefits, based on the load’s harmonic current profile, cost-of-power and loading.

The PQI Calculator™
Figure 1

The PQI Calculator™ will allow an engineer to compare any two transformers, each having the same or different kVA and voltage ratings, under the same or different harmonic current profiles, at any load level.

Programming

With reference to Figure 1, to make a comparison, the values shown in all dark gray windows must be completed. With reference to Figure 2, the first data entry screen allows the programmer to enter the project name, date and comparison scenario, kVA ratings, secondary winding information, published linear efficiencies, utility rates, air conditioning requirements, and transformer and/or installation costs.

Figure 2

The programmer then has the option of entering either the transformers' efficiencies, at a specific load, Figure 3, or their losses, Figure 4

Figure 3

Figure 4

The programmer must then enter the load’s harmonic current magnitudes. The default values, shown in Figure 5, are typical for single-phase, nonlinear switch-mode power supplies, as per IEEE Std 519-1992.

Figure 5

The programmer then has the option of entering the transformers’ Custom Load profile, Figure 6, or any one of four NEMA TP 1-2002 profiles, at a specified load level, Figure 7.

Figure 6

Figure 7

Computations

Once these selections have been made, The PQI Calculator™ will compute all values contained in the red and green windows, and generate loss and efficiency curves for both transformers under linear and nonlinear load conditions, Figures 8, 9 & 10.
 

Linear and Nonlinear Losses
75kVA K-13 Transformer vs. 75kVA Type GY Distribution TransFilter™
Figure 8

Linear Efficiencies
75kVA K-13 Transformer vs. 75kVA Type GY Distribution TransFilters™
Figure 9

Nonlinear Efficiencies
500kVA K-13 Transformer vs. 500kVA Type GY Distribution TransFilter™
Figure 10

With reference to Figure 1, The PQI Calculator™ shows the various outcomes when comparing the performance of two 75kVA transformers in a Custom Load scenario.

In order to display the Annual Savings, ROI and Payback, in a substitution scenario, the programmer has entered the Capital Cost for both transformers. The Annual Energy Savings, ROI and Payback, calculated by The PQI Calculator™, are based on transformer performance only.

System Performance

The reduction of harmonic currents and voltages in the remaining elements of the electrical distribution system will further reduce its ‘penalty losses’ and increase its efficiency. In medium to large distribution systems, these additional financial benefits can equal or exceed those produced by the application of Distribution TransFilters™ in isolation.

The PQI Solution™

Power Quality international, inc. uses The PQI Calculator™ to optimize the financial benefits of The PQI Solution™. This service is available on a free-of-charge basis. Please call PQI at (888) 539-7712 for additional information.