As an emergency power supply or main power supply, the starting method of
diesel generator sets directly affects the life of the equipment and the safety of operation. No-load starting is an industry standard operating specification, which requires that the unit is not connected to any load during the starting process, and gradually loads after the speed is stable and the voltage is normal. This article will analyze the technical principles, core functions and scientific basis of no-load starting for you.
1. Working principle of no-load starting
The no-load starting process of diesel generator sets can be divided into three stages:
Starting stage:
The starting motor drives the engine crankshaft to rotate, compressing the air in the cylinder to generate high temperature.
The injector accurately sprays diesel, which is mixed with high-temperature air and ignites spontaneously, pushing the piston to work.
Idle warm-up stage:
The engine speed is increased to 50%-70% of the rated speed (such as 1500rpm The idle speed of the unit is 800-1000rpm).
The oil pump establishes oil pressure to lubricate moving parts such as bearings and pistons to reduce friction losses.
Synchronous grid preparation stage:
The voltage regulator (AVR) stabilizes the generator output voltage to the rated value (such as 400V).
The frequency meter shows 50Hz (or 60Hz), and the phase is synchronized with the mains or load demand.
Technical key points: Under no-load condition, the engine only needs to overcome the internal friction resistance, and the load rate is 0%, which can achieve fast and stable start.
2. Four core functions of no-load starting
1. Protect the core components of the engine
Reducing mechanical shock: When starting with load, the engine needs to overcome the load torque, causing the crankshaft and connecting rod to bear instantaneous overload (peak stress increases by 30%-50%).
Avoid lubrication failure: The engine oil needs to form an effective oil film at a speed of ≥800rpm, and no-load starting can ensure that the lubrication system is fully established.
2. Ensure the stability of the electrical system
Voltage fluctuation control: Starting with load may cause a sudden drop in voltage (instantaneously drop to below 300V), causing the contactor to trip and the electronic equipment to restart.
Avoid reverse power risk: If there is residual voltage at the load end, starting with load may trigger reverse power protection and cause the unit to trip.
3. Extend equipment service life
Reduce thermal stress: The engine temperature rises slowly during no-load starting to avoid thermal shock caused by sudden load (the temperature difference of the cylinder head can exceed 100°C).
Reduce carbon deposit risk: Stable idling speed helps the fuel burn fully and reduces carbon deposits on the top of the piston.
4. Comply with safe operation specifications
Industry mandatory standard: GB/T 2820.5-2009 "AC generator set driven by reciprocating internal combustion engine" clearly requires that "the unit should run at no load for 3-5 minutes after starting".
Insurance clause constraints: Most equipment insurance regulations stipulate that damage caused by illegal start-up with load is not within the scope of compensation.
III. Potential hazards of starting with load
Engine damage:
Connecting rod bending: A data center was illegally started with load, resulting in deformation of the connecting rod, and the repair cost exceeded 100,000 yuan.
Turbocharger jamming: The exhaust temperature rises suddenly during load starting, which may burn the turbocharger bearing.
Electrical system failure:
Inverter alarm: Voltage fluctuation triggers UPS over-voltage and under-voltage protection, causing power outage of key loads.
Cable overheating: Instantaneous high current (up to 3-5 times the rated current) causes the cable insulation layer to melt.
Conclusion
No-load starting is the "first line of defense" for the safe operation of diesel generator sets. It provides reliable protection for emergency power supply by reducing mechanical shock, stabilizing electrical parameters, and extending equipment life. Enterprises should establish standardized operating procedures and combine intelligent control systems to achieve automatic protection to ensure that the units can be "pulled out, used, and stabilized" at critical moments.
More information:
http://www.huaquan168.com/
