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. 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.
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| Illustration 1 | g00627416 |
Allowable Combinations of Unbalanced Loads | |
Block Loading
The 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
- The amount of load
If derating is required in order to block load, refer to ISO 3046 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 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. This current is called the reactive load. This current does not require engine power to be maintained.
In most applications, electric motors and transformers determine the power factor of the system. Induction motors usually have a power factor of 0.8 or less. 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 goes up, the total current that is supplied to a constant power demand will go down. A 100 kW load that is at 0.8 power factor will draw more current than a 100 kW load that is at 0.9 power factor. A high power factor will result in a full engine load at less than the generator rated amperage. A lower power factor increases the possibility of overloading the generator.
Note: Cat generators are rated at a power factor of 0.8 unless the generator is specified otherwise.
Excitation System
The generator can use "SHUNT", "AREP", or "PMG" excitation systems.
Standby Electric Sets
Most standby units are installed with controls for automatic starting. Standby units start without an operator in attendance.
Standby units cannot automatically change the governor speed. Standby units cannot automatically change the setting of the voltage level. The governor speed and voltage level must be preset for the proper operation of that unit. Whenever the generator is operated manually, ensure that the settings for governor speed and voltage level are correct for automatic operation. Check all switches on the Standard Control Panel for the proper setting. Check all push buttons on the Premium Control Panel for the proper setting. On the Standard Control Panel, the Start Select Switch should be in the AUTOMATIC position. On the Premium Control Panel, the "AUTO" push button is pressed.
Generator Options
Battery Disconnect Switch
This switch is a single-pole switch. This switch cannot be used with dual electric starters.
Instrumentation
Three different remote start/stop panels are available. Extensions for the wiring harness are available in order to mount the panels. Contact your Cat dealer for more information.