Guide for Correctly Applying Load to A Diesel Generator Set

In modern industrial, commercial, and emergency power supply scenarios, diesel generator sets serve as core power sources. The rationality of their load matching directly impacts the stability, economy, and safety of equipment operation. Correctly applying load to a diesel generating set is crucial for ensuring its stable operation, extending its service life, and guaranteeing electrical safety. Below are the detailed steps and precautions for correctly applying load to a genset.

1. Preparations before applying load

Check diesel generator status: Confirm that the generator set has started normally and reached the rated speed and voltage (typically 1500 rpm/1800 rpm, voltage 400V/230V). Check whether parameters such as oil pressure, coolant temperature, and fuel level are within normal ranges. Ensure there are no abnormal noises, vibrations, or alarm signals from the generator set.

Check load equipment: Confirm that the total power of the load equipment does not exceed the diesel generator set's rated power. It is recommended to reserve a 10%-20% margin. Check the starting methods of the load equipment to avoid voltage sags caused by direct starting of high-power motors. Ensure the load equipment is properly grounded to prevent electric shock risks.

Connect the load: Use cables that comply with standards to connect the generator set to the load, ensuring the cable cross-sectional area is sufficient to avoid overheating. Adopt a step-by-step connection method: first connect low-power equipment, then gradually add high-power loads.

2. Steps for applying load to diesel generator

Gradually increase load: Start by powering light-load equipment (e.g., lighting, small motors) and observe whether the generator set's voltage and frequency are stable. Increase the load every 5-10 minutes, with each increase not exceeding 20% of the rated power, to avoid instantaneous overload. During the loading process, voltage fluctuation should be ≤ ±5%, and frequency fluctuation should be ≤ ±1%.

Monitor operating parameters: Continuously monitor instruments such as voltmeters, ammeters, and frequency meters to ensure parameters remain within rated ranges. Pay attention to parameters like exhaust temperature and oil temperature to avoid overtemperature operation. If a voltage sag, frequency fluctuation, or abnormal noise is detected, immediately reduce the load and investigate the cause.

Avoid sudden load application/removal: Sudden load application may cause voltage sags, frequency fluctuations, or even trigger protective shutdowns. Sudden load removal may cause overvoltage (triggering overvoltage protection), potentially damaging equipment.

3. Maintenance after applying load to generator set

Checks after stable operation: Confirm there are no fuel or coolant leaks from the diesel generator set. Check that the load equipment is operating normally, without overheating or abnormal vibrations.

Unloading steps: First reduce high-power loads, then turn off low-power equipment to avoid voltage surges. After unloading, let the diesel generator run at no-load for 3-5 minutes before shutting it down to allow for cooling.

Regular generator maintenance: Clean air filters and fuel filters, replace oil and coolant. Check key components such as battery charge and the starter motor. Maintain operation logs to analyze the impact of load variations on the generator set.

4. Precautions for special scenarios

Inductive loads (e.g., motors, transformers): The starting current for inductive loads can be 5-7 times the rated current, requiring sufficient power margin. Using soft starters or variable frequency drives is recommended to reduce starting impact.

Non-linear loads (e.g., UPS, VFDs): Non-linear loads generate harmonics, which may cause voltage distortion or overheating. It is necessary to install harmonic filters or select diesel generators with strong harmonic resistance capabilities.

Parallel operation: When operating multiple diesel generator sets in parallel, ensure voltage, frequency, and phase are synchronized to avoid circulating currents. Use synchronization controllers or parallel panels to achieve automatic synchronization.

By following the above steps and precautions, the safe and efficient operation of the diesel generator set under load can be ensured, extending equipment life and guaranteeing electrical safety.

Dingbo Power is a professional diesel generator manufacturer in China with almost 20 years’ production experience. We are an OEM supplier and provide high-quality diesel generators ranging from 5kW to 3000kW with a competitive price. Feel free to contact us with any questions, concerns, or inquiries to learn more about the products & services we provide.