Diesel Generator Set Components
Diagram 1: Composition of Diesel Generator Set
The diesel generator(Genset) set is composed of several systems including the engine, generator, safety monitoring, and controller.
- Engine: Converts chemical energy from fuel into rotating mechanical energy. such as Weichai, Shangchai, Cummins Engine ETC…
- Generator: Converts mechanical energy into electrical energy. also called Alternator, One of the best brands is Stamford alternator
- Speed Regulation System: Adjusts fuel supply to control engine speed and frequency of electricity, regulating output active power at a fixed frequency.
- Excitation Voltage Regulation System: Adjusts excitation current to regulate generator voltage (and reactive power and power factor in grid-connected generators).
- Controller: Manages local/remote start and stop of the generator, displays, records, and monitors operational parameters to ensure safe operation, and supports automatic synchronization and remote data transmission and control, along with operational logic settings for grid-connected operations.
Diesel Engine System Components
The engine consists of several subsystems: fuel supply and speed regulation, intake and exhaust, lubrication, cooling, and starting/charging systems.
- Fuel Supply and Speed Regulation System
- Components: Fuel pump, fuel filter, fuel cooler, injection pump, and injectors.
- Function: Supplies fuel timely, quantitatively, and under pressure into the combustion chamber. Controls engine operation at specified conditions via the injection pump and governor.
- Types: Plunger-type injection pump, PT fuel system, electronic injection (including common rail).
- Intake and Exhaust System
- Components: Air filter, intake/exhaust pipes, muffler, turbocharging system.
- Lubrication System
- Function: Supplies oil to reduce wear on friction surfaces, provides cooling, cleaning, sealing, and corrosion protection.
- Components: Oil pump, oil filter, centrifugal filter, regulating valves, lubrication pipes, oil cooler.
- Cooling System
- Function: Removes heat from combustion and friction to maintain optimal engine temperature.
- Types: Water-cooled (natural and forced circulation) and air-cooled systems.
- Components: Radiator, cooling fan, water pump, cooling strength regulator, antifreeze.
- Starting and Charging System
- Function: Converts external energy to initiate engine operation from rest.
- Methods: Manual, electric motor, compressed air, small gasoline engine. Electric motor starting is most common in data centers.
- Components: Electric motor, battery, charger.
Generator
The generator operates based on electromagnetic induction, where a conductor moving in a magnetic field generates induced voltage:
E=BVL=4.44fϕE = BVL = 4.44f\phiE=BVL=4.44fϕ
- E: Induced voltage
- B: Magnetic field strength
- V: Conductor speed
- L: Effective length of conductor in magnetic field
- f: Generator frequency
- ϕ\phiϕ: Magnetic flux per pole
Generators are categorized by voltage into low voltage (0.4KV) and high voltage (10.5KV). Structurally, they comprise a stator, rotor, excitation system, and control system.
When loaded, the magnetic field strength B decreases due to armature reaction, lowering induced voltage E. To stabilize terminal voltage, a DC excitation system (excitation source, AVR/DVR, excitation generator, three-phase rectifier diodes) adjusts excitation current. Excitation systems are either self-excited or separately excited, with separately excited systems preferred in data centers for their stability under non-linear loads.
Generator Set Controller
The main functions of the generator set controller ensure safe and efficient operation:
- Local/remote switching
- Starting the set
- Monitoring and displaying engine and generator parameters (speed, oil pressure, voltage, current, water temperature, battery voltage) with warnings and protection for anomalies
- Stopping the set
- Automatic synchronization
- Setting operational logic for grid-connected sets
Operating Conditions of Diesel Generator Sets
According to GB/T2819 “General Technical Conditions for Mobile Power Stations,” the generator set operates reliably and outputs rated power under specific environmental conditions.
| Environmental Condition | Absolute Atmospheric Pressure (kPa) | Ambient Temperature (°C) | Relative Humidity (%) | Remarks |
|---|---|---|---|---|
| First Condition | 100 (100m altitude) | 25 | 30 | |
| Second Condition | 89.9 (1000m altitude) | 40 | 60 | |
| Third Condition | ≤4000m altitude | Upper limit 40/45/50 | Lower limit -15/-25/-40 | Dew and mold |
Output power correction is allowed.
Power Rating of Diesel Generator Sets
- Rating Standards
- Continuous Power (COP): Maximum power for continuous operation under specified conditions, with no time limitation annually.
- Prime Power (PRP): Maximum power for variable load continuous operation, with no time limitation annually. Average power output over 24 hours should not exceed 70% of PRP.
- Limited-Time Running Power (LTP): Maximum power for up to 500 hours of operation annually.
- Emergency Standby Power (ESP): Maximum power for up to 200 hours annually during utility power interruptions, with each run typically not exceeding 1 hour. Average power output over 24 hours should not exceed 70% of ESP.
- Power Ratings (GB/T2820.1 and ISO8528.1)
- Continuous Power (COP): Maximum power for continuous, constant load operation.
- Prime Power (PRP): Maximum power for continuous, variable load operation, with average power output not exceeding 70% of PRP.
- Limited-Time Running Power (LTP): Maximum power for up to 500 hours annually.
- Emergency Standby Power (ESP): Maximum power for variable load operation during utility interruptions, with average power output not exceeding 70% of ESP.
Power Correction for Diesel Generator Sets
Actual output power needs correction when operating under non-standard conditions:
Pg=Ƞ(K1⋅K2⋅Pe−Np)Pg = Ƞ(K1·K2·Pe – Np)Pg=Ƞ(K1⋅K2⋅Pe−Np)
- Pg: Generator output power (KW)
- Pe: Rated power of the diesel engine under standard conditions (KW)
- K1: Long-term operation power correction factor (0.9 for long-term, 1 for <12 hours)
- K2: Environmental condition correction factor
- Np: Power loss due to fans and auxiliary equipment (KW)
- Ƞ: Generator efficiency (94%-95%)
Environmental condition correction factors are based on temperature, altitude, and humidity:
- For every 5°C increase in ambient temperature, output power decreases by 2%-3%.
- For every 500m increase in altitude, output power decreases by 4%-5%.
- Humidity has minimal impact, generally reducing output power by no more than 2%.