What Factors Should be Considered When Choosing a Generator Set

Generators are widely used in our life. For example, they are used in the agriculture machine, such as the tractor. It is an important tractor parts. Since it is very important, so how to choose a right generator set?

 

Several factors should be considered when choosing a generator set, which mainly includes mechanical and electrical performance, the purpose of the unit, the capacity and change range of the load, the use of the unit's environmental conditions (including altitude, climatic conditions, noise), and automation functions. Because diesel generator sets can be used in three situations: common, standby and emergency, the requirements for diesel generator sets are different according to different uses.

Selection of Common Generator Sets

Common generators have long continuous working hours, large changes in load curves, and the choice of unit capacity, number, type, and control method of the unit are different from emergency units.

(1) Determination of capacity: According to the long-term continuous operation, the output power can meet the maximum calculation load selection of the entire project, and the capacity of the standby unit of the generator set should be determined according to the importance of the load. The continuous output power of a diesel engine is generally 0.9 times the nominal power.

 

(2) Determination of the number of units: The general setting is usually more than two units to ensure the continuity of power supply and adapts to changes in the load curve of electricity consumption. Only with a large number of generating units can the number of generating units put into operation be determined according to the change in the power load, so that diesel engines are often operated under economic loads to reduce fuel consumption and reduce power generation costs. The best economic operating state of a diesel engine is between 75% -90% of the rated power. In order to ensure the continuity of power supply, the common unit itself should be considered to set up a standby unit.

 

(3) Determination of rotation speed: In general, high speed units with a rotation speed of 1000 to 1500 rpm should be selected for general civilian use, and low speed units with a rotation speed of 300 to 350 rpm are suitable for use as marine main engines.

 

(4) Determination of voltage: The determination of the output voltage of the generator is the same as that of the emergency generator set, which is generally 400V. Individual projects with large power consumption and long transmission distances can choose high-voltage generator sets.

 

Selection of Standby Generator Set

The sum of the load capacity, when the calculated load after multiplying by the required coefficient is less than the capacity of the emergency diesel generating set, the reserve factor is considered to be 1.2, that is, 1.2 times the calculated capacity is less than the capacity of the emergency diesel generating set. The unit supplies power to the load after mains power failure. When the sum of the load capacity and the calculated load after multiplying the required coefficient is greater than the capacity of a single emergency diesel generator set, two automatic generator sets with the same model, the same capacity, and similar voltage and speed characteristics can be selected. After the mains power is cut off, one or two units will supply power to domestic and commercial electricity. When the mains power is cut off and a fire occurs, the two sets will supply power to the fire-fighting load to facilitate fire fighting.

 

 

Selection of Emergency Generator

Emergency generators are generally suitable for high-speed, supercharged, low fuel consumption, and same-capacity generator sets. High-speed turbocharged diesel engines have a large single-unit capacity and occupy a small space. Diesel engines are equipped with electronic or hydraulic speed regulators for better speed regulation performance. Generators should be equipped with synchronous motors equipped with brushless excitation or phase-complex excitation for reliable and faulty operation. The rate is low and the maintenance is convenient. When the capacity of a single air conditioner or the motor is large in the first-level load, a third-harmonic excitation generator set should be selected. The machine is assembled on a common chassis with shock absorbers, exhaust smoke mufflers should be installed at the pipe outlet to reduce the impact of noise on the surrounding environment.

 

(1) Determination of capacity: The emergency generator set is used for emergency purposes, and it is often in the standby emergency starting state, and the continuous operation time is not long, generally it does not exceed 8h, so the capacity can be determined according to "backup power". According to the sum of the capacity of the first-stage load (excluding the reserve capacity), the revised unit capacity is considered, and the starting requirement of the largest motor in the first-stage load can be met, and the capacity of the emergency diesel generator set is determined accordingly. Emergency generators generally use three-phase AC synchronous generators with a nominal output voltage of 400V.

 

(2) Determination of the number of units: Generally, one generator set with automation, rotation speed of 1000-1500 rpm, brushless excitation, 400 / 230V, three-phase four-wire with control screen, charging and discharging equipment and shared chassis is selected. A common chassis with a daily fuel tank can be required to reduce piping and footprint. In addition, from the perspective of reliability, two units can also be selected for power supply in parallel. Generally, the number of generator sets for emergency use should not exceed three. When multiple units are selected, the units should try to use complete sets of equipment with the same model and capacity, similar pressure and speed characteristics, and the fuel properties used should be the same for maintenance and shared spare parts.