HOUSING 8U5724 - 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 process allows the engine to work at the rated capacity. An electrical unbalance can result in an electrical overload and overheating if one phase current exceeds the nameplate amperage.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 LoadsBlock Loading
When an electrical load is applied to a generator set, block loading occurs. 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
the amount of load that is already present If a block load derating is required, refer to ISO 8528 Standards or SAE J1349 Standards. Power Factor
The power factor represents the efficiency of the load. The power factor is the ratio of apparent power to total power. This ratio is expressed as a decimal. The power factor represents the 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. This current is called the reactive load. Engine power is not required to maintain the reactive load.In most applications, electric motors, solid-state controls, and transformers determine the power factor of the system. Induction motors usually have a power factor that is no larger than 0.8. Incandescent lighting is a resistive load of about 1.0 power factor, or unity. Solid-state controls (motor starters), variable frequency drivers, variable speed drivers, and UPS systems can operate at any power factor, leading, or lagging. In this case, the power factor can be between 0.4 and 1.0.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. With equal loads, a lower power factor will draw more current. A high-power factor will result in full engine load that is less than the generator rated amperage. A lower power factor increases the possibility of overloading the generator.Note: Normally, Cat generators are designed for a power factor of 0.8 lagging. Consult your Cat dealer in order to check the generator rating if operation at less than 0.7 lagging power factor is desired.Excitation Systems
Self-Excited Generators
Self-excited generators receive excitation power and regulator-voltage sensing from the generator main armature output. The voltage regulator senses the generator output voltage. A regulated output is provided to