How to choose a diesel generator set

The factors that should be considered when selecting a diesel generator unit mainly include mechanical and electrical performance, the purpose of the unit, the capacity and range of load variation, the environmental conditions of the unit's use (including altitude, climate conditions, noise), automation functions, etc. Due to the fact that diesel generator sets can be used in three situations: commonly used, standby, and emergency, the requirements for diesel generator sets vary for different purposes.

① The selection of commonly used diesel generator sets.

The commonly used generator sets have a long continuous working time and significant changes in the load curve. The selection of unit capacity, number of units, type, and the control method of the unit are different from those of emergency units.

② Selection of standby diesel generator sets.

When the calculated load is less than the capacity of the emergency diesel generator set after multiplying the sum of load capacities by the demand factor, the standby factor is considered to be 1.2, that is, 1.2 times the calculated capacity is less than the capacity of the emergency diesel generator set. After a power outage, the emergency generator set supplies power to the load. When the calculated load is greater than the capacity of a single emergency diesel generator set after multiplying the sum of load capacities by the demand factor, two automatic generator sets of the same model, capacity, and similar voltage and speed regulation characteristics can be selected. After a power outage in the city, one or two units provide power to domestic and commercial electricity; When there is a power outage and a fire occurs, two units supply power to the firefighting load for the convenience of firefighting.

③ The selection of emergency diesel generators.

Emergency diesel generators are generally recommended to use high-speed, turbocharged, low fuel consumption, and diesel generator sets of the same capacity. The high-speed turbocharged diesel engine has a large single unit capacity and occupies little space; Diesel engines are equipped with electronic or hydraulic speed control devices, which have good speed control performance; Synchronous motors equipped with brushless excitation or phase compound excitation devices should be selected for generators, which are more reliable, have a low failure rate, and are easier to maintain and repair; When the capacity of a single air conditioner or motor is large in the first level load, it is advisable to choose a generator set with third harmonic excitation; Assembled on a shared chassis with shock absorbers; Silencers should be installed at the exhaust pipe outlet to reduce the impact of noise on the surrounding environment.

④ The selection of the starting method for the unit.

There are three ways to start a diesel engine: ① manual start; ② Electric starting; ③ Compressed air starting. It is advisable to use electric starting method in high-rise buildings and avoid using compressed air starting method. In a type of high-rise building, it is necessary to choose a diesel generator set with a self starting device. Once the power supply to the city grid is interrupted, it must be supplied within 15 seconds (high regulations require 30 seconds). When conditions permit in Class II high-rise buildings, it is also advisable to use units with self starting devices. If there are difficulties, manual starting devices can also be used.

Attention should be paid to matching with three-phase motors. When selecting the capacity of a diesel generator set and a three-phase motor, it is recommended to consider a safety factor of 1.5, which is 1.5 times the motor capacity (it must be a soft start method). Pay attention to the relationship between rated power and reserve power, as well as the relationship between KVA and KW. KVA is the apparent power, KW is the effective power, and their relationship is IKVA=0.8KW. Imported units are generally represented by KVA for power units, while domestic electrical equipment is generally represented by KW.

Recognizing the machine