Characteristics and purchase requirements of diesel generators

Diesel generator is a small power generation equipment that refers to a power machinery that uses diesel as fuel and diesel engine as the prime mover to drive the generator to generate electricity. The entire unit is generally composed of diesel engine, generator, control box, fuel tank, starting and control battery, protection device, emergency cabinet and other components. Below is a brief introduction to the characteristics and purchase precautions of diesel generators:

1、 The two main characteristics of emergency diesel generators:

The first characteristic is to respond to urgent needs, with a short duration of continuous operation, usually only requiring a few hours of continuous operation (≤ 12H);

The second characteristic is to serve as a backup. The emergency generator set is usually in a shutdown waiting state. Only when the main power supply is completely blocked and cut off, the emergency diesel generator set will start running to supply emergency electricity load. When the main power supply is restored to normal, it will immediately switch to shutdown.

2、 Key points for selecting emergency diesel generators

(1) Determination of emergency diesel generator capacity

The rated capacity of the emergency diesel generator set is the 12 hour rated capacity after atmospheric correction, and its capacity should be able to meet the total calculated load of emergency electricity. It should be verified according to the generator capacity that can meet the requirements of starting a single maximum capacity electric motor in the first level load. Emergency generators generally use three-phase AC synchronous generators, with a calibrated output voltage of 400V

(2) Determination of the number of emergency diesel generator sets

When there are multiple backup generator sets, generally only one emergency diesel generator set is set up. From reliability considerations, two sets can also be selected for parallel power supply. The number of urgently needed generator sets should generally not exceed 3. When selecting multiple units, it is advisable to choose a complete set of equipment with the same model and capacity, similar pressure and speed regulation characteristics, and consistent fuel properties for maintenance and shared spare parts. When there are two urgently needed generator sets in supply, the self starting device should enable the two sets to serve as backup for each other. That is, after the delay confirmation of the mains power failure and power outage, a self starting command should be issued. If the first set fails to self start for three consecutive times, an alarm signal should be issued and the second diesel generator should be automatically started.

(3) Selection of emergency diesel generators

Emergency units should choose diesel generators with high speed, turbocharging, low fuel consumption, and 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; The exhaust pipe outlet should be installed to reduce the impact of noise on the surrounding environment.

(4) Control of emergency diesel generator set

The control of emergency diesel generator sets should have fast self starting and automatic switching devices. When the main power supply fails and loses power, the emergency unit should be able to quickly start and restore power. The allowable power outage time for the first level load ranges from tens of seconds to tens of seconds