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Entering Loads Definition of Terms APPENDIX A Rev. Jan 2011 Application Manual – Liquid Cooled Generator Sets A minimum of 10 percent overload capability is available for prime power ratings per engine rating standards BS 5514 and DIN 6271. Not every generator set configuration is available for prime duty. When generator sets are paralleled with a utility service for an extended period of time, they should not be operated in excess of their base load rating. Generally the base load rating of a generator set is significantly lower than its prime power rating. Base load ratings for generator sets are available from the factory or your local Cummins Power Generation distributor. Voltage Available voltage choices are a function of selected frequency. Default values are 277/480, Series Wye. The next and most important step in sizing a generator set is identifying every type and size of load the generator set will power. As with most operations in GenSize, the loads can be entered either from the menu under Projects, Add New Load, or from the icons located on the tool bar. After selecting a load type, the load entry form will appear. Each load form will open with load characteristic defaults which can all be changed. Enter all of the required information. If you are unsure what any of the items are, check the online Help for an explanation. As each load is entered, they will appear in a list on the left side of the screen under the project you are working on. Selecting (with a mouse click) one of the loads in the list will display the load operating characteristics on the right of the screen. Double clicking a load icon will open the load entry form for that load and you can edit the load from here. The following is intended to help you understand load parameters and the way they are calculated by GenSize. Identify all of the different type and size loads the generator set will need to support. If you have more than one load of a given size and type, you only need to enter it once, unless you want each of the loads to carry a different description. The quantity of each load can be set when you enter the load in the step starting sequence. As described later in this section Cummins Power Generation has researched the starting and running characteristics of many of the common loads and have included defaults for these load characteristics in GenSize. You can choose to use the defaults or, if you know the characteristics of your load are different, change the load characteristic. If you have a load type other than what is identified in GenSize, use a miscellaneous load to define the load starting and running requirements. Based on the load characteristics, GenSize calculates values for running kW (RkW), running kVA (RkVA), starting kVA (SkVA), starting kW (SkW), starting power factor (SPF), peak kVA (PkVA), peak kW (PkW), and running amps (RAmps). When non–linear loads are present, it may be necessary to over–size the alternator, and GenSize calculates a value for the alternator kW (AkW) for the load. Note that when entering single–phase loads on a three–phase generator set, GenSize assumes that all three phase loads will be balanced among the three phases. Therefore, the single–phase loads are converted to an equivalent three–phase load for sizing purposes. This results in the single–phase load current being distributed across the three phases so the single–phase load current is divided by 1.73. When a single phase load is entered for a three phase set application, the actual single phase current will be displayed in the load entry form, but when the load is entered into a step (the step load is the balanced load applied to the generator), the step load current is converted to the equivalent three phase current. The following abbreviations are used in GenSize for calculating individual load running and starting requirements, step load requirements, and transient surge load requirements. These abbreviations are used on load forms and reports in the application and in the following discussion intended to document some of the calculations performed in GenSize. A–7
Application Manual – Liquid Cooled Generator Sets Load Running Requirements (Individual Load Steady–State Running) • Running kVA (RkVA) – the running kilovolt–amperes load. • Running kW (RkW) – the running kilowatt load. • Alternator kW (AkW) – the alternator capacity provided to compensate (to oversize) for non–linear distortion. • Running PF (RPF) – the steady–state running power factor of the load. • Efficiency – the ratio of output power to input power. • Running Amps (RAmps) – the running amperes for a load or step. Load Starting Requirements (Individual Load Starting) • Starting kW (SkW) – starting kilowatts of a load. • Starting kVA (SkVA)– starting kilovolt–amperes of a load. • Starting PF (SPF) – starting power factor is the power factor of the load at the time it is initially energized or started. Transient Step Load Requirements (Combined Load in Each Step Load Application) • Maximum Step kW – the maximum step load in kW (sum of individual load starting kilowatts (SkW)) in the step. • Maximum Step kVA – the maximum step load in kVA (sum of individual load starting kilovolt–amperes (SkVA)) in the step. • Cumulative Step kW – the Maximum Step kW added to the running kW of the previous step(s). • Cumulative Step kVA – the Maximum Step kVA added to the running kVA of the previous step(s). • Effective Step kW – the Cumulative Step kW times a multiplier to account for the reduced load effect due to sustained reduced output voltage during the transient step load. • Effective Step kVA – the Cumulative Step kVA times a multiplier to account for the reduced load effect due to sustained reduced output voltage during the transient step load. Transient Surge Load Requirements (Combined Load for all Loads that Require Random Peak Operating Power) • Peak kW (PkW) – the sudden increase of power in kW demanded by a cyclical load as it starts, or by other surge loads like welders and medical imaging equipment when they operate. • Peak kVA (PkVA) the sudden increase of power in kVA demanded by a cyclical load as it starts, or by other surge loads like welders and medical imaging equipment when they operate. • Cumulative Surge kVA – the Peak kVA added to the running kVA of all other non– surge loads. • Cumulative Surge kW – the Peak kW added to the running kW of all other non–surge loads. A–8 APPENDIX A Rev. Jan 2011
Page 1 and 2: Chapter 8 Appendices
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Page 25 and 26: LINE APPENDIX B 3 2 1 Autotransform
Page 27 and 28: LINE 3 2 1 APPENDIX B MOTOR STARTIN
Page 29 and 30: APPENDIX B FULL-VOLTAGE KVA CURVE k
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