Traditional market sizing programs use simple rule of thumb multipliers to size the generator for non-linear loads. Given the vast variation between different types of loads from different manufacturers, simple multiplier sizing is just not adequate for today’s complex loads. Power Design Pro utilizes harmonic analysis to limit the harmonic voltage distortion to acceptable levels.
The program automatically selects an appropriate harmonic current signature for each load type but gives the user the ability to modify it to accurately model any load. Once the loads are entered, Power Design Pro calculates the resulting harmonic voltage distortion as that load is applied to various generators.
Accurate Load Modeling
Does your current sizing software ask questions applicable to your application, such as: Is the UPS technology passive, line interactive, ferroresonant, or double conversion? Is the variable frequency drive input 6 pulse unfiltered, filtered, or IGBT? How many compressor motors are being utilized in that 100-ton chiller system and is reheat being applied?
Most sizing programs don’t. How can a load’s true nature be accurately captured without asking the pertinent questions? The Power Design Pro system approach expertly provides safe default settings when specific information is limited while incorporating applicable questions in order to model the load’s true characteristics. For unusual applications, Power Design Pro allows users to build their own load types inclusive of starting, running, and harmonic characteristics.
When designing redundant power solutions, load shedding schemes are often implemented to maintain system integrity. Power Design Pro provides the ability to shed loads that are entered into the program and allows the user to evaluate the effects of running those loads against any generator configuration the user selects. The goal is not to simply provide a sizing recommendation, but provide an in-depth analysis tool that allows the user to compare multiple scenarios for the best possible solution.
Natural Load Sequencing, Cyclic Loading, and Load Factors
A common limitation and misapplication of traditional sizing programs occurs when too many loads are entered into a single step, resulting in a fictitious situation that assumes all the loads are running and starting simultaneously. To cope with this limitation, users were forced to manipulate the loads into some arbitrary load groupings. Power Design Pro easily overcomes this issue by supporting natural load sequencing, cyclic loading, and user definable load factors in addition to the traditional concurrent starting-load step method.
Most sizing programs use a simple voltage dip model to analysis motor starting transients and provide very limited analysis. Power Design Pro uses voltage and frequency tolerances that are customized for each load versus a single parameter for the entire project. It also provides the user with a detailed transient analysis, which identifies the load sequences and the loads in that sequence that are causing the greatest system transients – voltage and frequency.