XQ400 Power Module Caterpillar


Generator Operation

Usage:

XQG400 AL5

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. The equal load 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 1g00627416
Allowable Combinations of Unbalanced Loads

Block 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, Caterpillar generators are designed for a power factor of 0.8 lagging. Consult your Caterpillar dealer in order to check the generator rating if operation at less than 0.7 lagging power factor is desired.

Excitation Systems

Permanent Magnet Pilot Excited Generators

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 stator. The pilot exciter operates independently from the generator output voltage. Constant excitation during a large load application is possible because the irregularities that occur in the generator output voltage are not fed back into the excitation system. Such irregularities can be caused by load conditions. The independent operation also allows the generator to sustain an overload for a short duration better.

Low Idle Adjustment

The low idle on generator sets is typically 900 revolutions per minute. On 60 Hz units, low idle will be approximately 66 percent of the full load speed.

There is no low idle stop on generator sets with electronic governors. Low idle is set at the factory for generator sets with mechanical governors. The low idle is set at the factory for generator sets that are powered by natural gas. The low idle should only be adjusted by your Caterpillar dealer if adjustment is required.

Note: Operating the electric set at low idle speed for an extended time will cause some voltage regulators to shut off. The electric set must be completely shut down. Then, the electric set must be restarted. This process will allow the voltage regulator to produce an output again.

Standby Generator Sets

Most standby units are automatic. Without an operator in attendance, standby units will perform the following functions: start, pick up the load, run and stop.

Standby units will not change the governor speed control or voltage level settings automatically. The governor speed and voltage level must be preset for the proper operation of that unit. Whenever the set is operated manually, ensure that the governor speed and the voltage level settings are set correctly for automatic operation. Check all switches for the proper setting. The "Start Selector Switch" should be in the AUTOMATIC position. Emergency Stop Switches should be in RUN position.

Generator Options

Space Heaters

Most of the SR4B generators are provided with space heaters. These space heaters are installed for operation in all climates. The space heaters are especially useful in climates with high humidity. For more information on space heaters, refer to Maintenance Section, "Space Heater - Check".

Load Pan Door

Note: The section below only applies to the XG400 Generator Set.

The load pan door provides user access to both generator load connections, terminals, and connectors for customer interconnect wiring. There are two safety features regarding this access door that enhances personnel safety.

Auto-lock Feature

Note: The section below only applies to the XG400 Generator Set.

An electronically controlled dead-bolt type lock is provided to lock the door automatically. This lock prevents access to the load connection bus bars while energized. The onboard EMCP genset controller senses the bus voltage and energizes the locking mechanism.

Breaker Trip Feature

Note: The section below only applies to the XG400 Generator Set.

A switch is used to detect the load pan door is closed. This switch is used to prevent the onboard generator breaker from closing if the load pan door is open. The feature prevents the breaker from closing by issuing a trip signal directly to the breaker.

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