HOUSING 4W0249 - Caterpillar

Loading of the Generator
When a generator is installed or reconnected, be sure that the total current in one phase does not exceed the nameplate rating. Each phase should carry the same load. This allows the engine to work at the rated capacity. If one phase current exceeds the nameplate amperage, an electrical unbalance can result in an electrical overload and overheating.Allowable combinations of unbalanced loads are shown in Illustration 1. When you operate with significant single-phase loads, the combinations of single-phase load and three-phase load may be used. Such combinations should be located below the line on the graph.
Illustration 1 g00627416
Allowable Combinations of Unbalanced Loads
Block Loading
Block loading is the instantaneous application of an electrical load to a generator set. This load may be anywhere from a moderate percentage of the rated load up to the rated load.The block loading capability of a generator set depends on the following factors.
Engine transient response
Voltage regulator response
Type of the voltage regulator
Altitude of operation of the generator set
Type of load (power factor for the load)
The percentage of load before the application of the block loadIf derating for the block load is required, refer to ISO 3046 Standards or SAE J1349 Standards. Also, reference Engine Data Sheet, LEKX4066, "Loading Transient Response" and Engine Data Sheet, LEKX4067, "Block and Transient Response".Note: ISO stands for International Standards Organization.Power Factor
The power factor represents the efficiency of the load. Power factor is the ratio of apparent power to total power. The power factor is expressed as a decimal. The power factor represents that portion of the current which is doing useful work. The portion of current which is not doing useful work is absorbed in maintaining the magnetic field in motors or other devices.In most applications, electric motors and transformers determine the power factor of the system. Induction motors usually have a 0.8 or smaller power factor. Incandescent lighting is a resistive load of about 1.0 power factor, or unity.The power factor of a system may be determined by a power factor meter or by calculations. Determine the power requirement in kW by multiplying the power factor by the kVA that is supplied to the system. As the power factor increases, the total current that is supplied to a constant power demand will decrease. For example, a 100 kW load at a 0.8 power factor will draw more current than a 100 kW load at 0.9 power factor. High power factor will result in full engine load at less than the rated amperage of the generator. A lower power factor increases the possibility of overloading the generator.Note: If no other power factor is specified, Caterpillar generators are designed for a 0.8 lagging power factor.Excitation Systems
Permanent Magnet Pilot Excited Generators
Note: The PMPE generator is standard.Permanent Magnet Pilot Excited (PMPE) generators receive power for the voltage regulator from a pilot exciter, rather than the main armature. The pilot exciter consists of a permanent magnet rotor and a permanent magnet stator. The pilot exciter operates independently from the generator output voltage. Constant