Essential Daily Knowledge for Prime Diesel Generators

Generator Manufacturer Explains: Essential Daily Knowledge for Prime Diesel Generators

When estimating the required capacity for a Prime Diesel Generator set—meant for long-term continuous operation—it must be sized to handle the site's maximum calculated electrical load. According to the Chinese national standard GB1105.1-1987 ("Test methods for internal combustion engines – Standard reference conditions, declarations of power, fuel, and lubricating oil consumption"), the rated power of a diesel engine is defined under standard environmental conditions (atmospheric pressure=100kPa, relative humidity=30%, ambient temperature=25°C, intercooler coolant inlet temperature=25°C) as the power it can sustain for a minimum of 15 minutes.

However, environmental factors significantly impact performance. In conditions of high altitude or humidity, air density decreases. This reduces the oxygen supply for combustion, necessitating a downward adjustment (derating) of the generator's output power. Therefore, the selected generator's power rating must be higher than the total load requirement to compensate for this power loss in non-standard conditions. Power correction calculations for the diesel engine are essential.

Under standard conditions, the sustainable continuous output power for a diesel generator is typically 0.9 times its rated power. Choosing the wrong size has serious consequences:

• Undersizing: A generator with insufficient capacity will fail to power all loads or may stall when starting large equipment.

• Oversizing: An excessively large generator leads to higher initial investment, increased maintenance costs, and wasted resources. Moreover, running a diesel engine consistently at very low loads (underloading) is detrimental. It causes severe carbon buildup in piston rings and injector nozzles, accelerates cylinder wear, and can lead to premature engine failure.

It's also crucial to understand load types, as they affect the required generator capacity:

• Resistive Loads: Devices like light bulbs, electric stoves, or ovens. Their resistance is relatively constant, and current decreases proportionally with voltage.

• Inductive (Reactive) Loads: Equipment like machine tools, water pumps, or large motors. These require extra power (surge current) to start and establish their magnetic fields.

The presence of inductive loads, in particular, means the generator's capacity must be recalculated, not just based on the sum of wattages. The generator must handle both the running watts and the higher starting (surge) demands of such equipment to ensure reliable operation.