appendix

More documents

Recommendations

Info

APPENDIX A Application Manual – Liquid Cooled Generator Sets Site Rated Max SkW and Max SkVA Displays the site–rated (derated when necessary for altitude and ambient temperature) maximum SkW and SkVA the generator set configuration can accommodate. If the display is red, the generator set cannot recover to a minimum of 90 percent of rated voltage with required Step or Peak load. One of the sizing philosophies for surge loading is that, with the surge load applied, the generator set must be able to recover to 90 percent of rated voltage so that motors can develop adequate accelerating torque. If the generator set recovers to 90 percent of rated voltage, a motor will develop 81 percent of rated torque, which has been shown by experience to provide acceptable motor starting performance. If the display is yellow, the generator set can recover to a minimum of 90 percent of rated voltage with required surge load, but only because the surge requirement has been reduced. GenSize will reduce the surge requirement in recognition of the fact that the generator set output voltage is reduced while loads having starting power requirements approaching the maximum generator set capacity are starting. Temperature Rise At Full Load Displays the temperature rise the alternator will not exceed while supplying load up to and including the generator set full–load rating. Each individual generator set model will have one or more of the following temperature rise alternators available which may be specified in the current project parameters: 80° C, 105°C, 125° C and 150° C. Of course, the actual temperature rise of an alternator is a function of actual connected load. Therefore, GenSize may recommend a generator set with a lower or higher temperature rise option than specified in the New Project Parameters since the set recommendation is based on connected load. Connected load may be less than the full generator set capacity or, in the case of non–linear loads, the alternator may be required to be rated at greater than the set capacity. In any case, the set recommendation will limit the alternator temperature rise to that specified in the New Project Parameters. Excitation Displays the type of excitation system to be supplied with a generator set. If the display is red, the generator set is shunt excited and the percentage of non–linear load exceeds 25 percent of the load running requirement, RkW. The PMG excitation system is recommended for applications that have a high–linear load content. Unless the PMG option is unavailable, Cummins Power Generation does not recommend using shunt excited generator sets if the non–linear load requirement is more than 25 percent of the total load requirement. The non–linear load requirement is calculated by adding the Running kW from all of the loads where Alternator kW exceeds Running kW. This will be the case for UPS loads, variable frequency motors, and solid state motor starters which are not equipped with an automatic bypass. This Alternator kW sum is then divided by the sum of the Running kW from all of the loads. Why a generator set may not be recommended: Several factors can cause a generator set to not be recommended. • Running kW requirement may exceed the rating of the generator set. Project parameters such as altitude, ambient temperature and prime power duty may cause the generator set to be derated and fall below project requirements. • The Running kW may be below the minimum of 10 to 30 percent of rated generator set capacity, as specified in the current project parameters (30 percent is default, as recommended by Cummins Power Generation). • The surge kW requirement may exceed generator capacity, which may have fallen below project requirements because of derating for altitude and ambient temperature. GenSize uses the greater Cumulative kW and Peak kW to determine the load surge kW. Rev. Jan 2011 A–19
Application Manual – Liquid Cooled Generator Sets • The surge kVA exceeds generator set capacity. The surge kVA requirement is similar to the surge kW requirement except that there is no derating for altitude or ambient temperature. GenSize uses the greater of cumulative kVA and Peak kVA (if any) to determine the load surge kVA requirement. • The alternator kW required exceeds the alternator capacity, which may be derated for altitude and ambient temperature by the project parameters. The altitude knee for alternators, however, is 1000m (3280 ft) and the temperature knee 40° C (104° F). Alternator kW will be derated 3% per 500m (1640 ft) of altitude above the knee and 3% per 5° C (9° F) of ambient temperature over the knee. • The alternator kVA required exceeds alternator capacity, which can be derated by altitude and temperature in the same way as the alternator kW. • The total non–linear load requirement exceeds 25 percent of the total load requirement. This will exclude shunt–excited generators where PMG excitation is not available. The total non–linear load requirement is the sum of the Alternator kW values of all of the non–linear loads. • The calculated voltage and frequency dips exceed the limits set in the current project parameters. • Starting voltage dip is calculated using the higher of two values: dip based on the maximum Step kW or on the maximum step kVA. • Peak voltage dip is calculated only if loads in the project exhibit a running surge (cyclic loads or loads like medical imaging that have a high peak power requirement when they are operated. • Frequency dip is calculated using the higher of two values: maximum Step kW or Peak kW from loads which exhibit running surge. • The message, “No generator set is available that meets your running load requirements” usually means that something in the New Project Parameters has been changed after having specified the running load. For instance, you will get the message if you change from diesel to natural gas fuel or from no sound attenuation to Quite Site and the running load you had specified exceeds the capacity of the largest natural gas or Quite Site generator set available. It may also mean that your project falls into a “gap” in the Cummins Power Generation product line. At this point, lowering the minimum percent rated load in the project parameters could allow a recommended set. If this is the case, contact your local Cummins Power Generation distributor for help. • The message, “No generator set is available which meets your frequency or voltage dip requirements” generally means that the surge requirement of some load step is forcing selection of such a large generator set that the steady state running load falls below 30 percent of the generator set capacity. Since Cummins Power Generation does not recommend running at less than 30 percent of rated capacity, no set can be recommended. At this point, you may have several choices: • Increase the allowable voltage or frequency dip. • Reduce the minimum percent rated load to less than 30 percent. • Apply loads in more steps to lower the individual step surge load. • Provide reduced–voltage motor starting. • Parallel generator sets. • Add loads that do not have a high starting surge (lights, resistive loads, etc.). A–20 APPENDIX A Rev. Jan 2011
Page 1 and 2: Chapter 8 Appendices
Page 3 and 4: Application Manual - Liquid Cooled
Page 19: Application Manual - Liquid Cooled
Page 23 and 24: APPENDIX B CONTENTS APPENDIX B CONT
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
Page 55 and 56: Application Manual -- Liquid Cooled
Page 57 and 58: Application Manual -- Liquid Cooled
Page 59: Application Manual -- Liquid Cooled

appendix

Create successful ePaper yourself

Delete template?

Save as template?