# Design Elements of Diesel Generator Sets Multi Unit Parallel Connection

Sep. 01, 2022

Nowadays, the society's demand for electricity is increasing, and the diesel generator set as a backup power source and an emergency power source is also facing the trend of increasing capacity demand. Sometimes a single generator set can no longer meet the demand, and there must be two generator sets. Or more than two diesel generator sets can be used in parallel to meet the needs of the load. So, when is the size of the generator set needed, and how many units are suitable for parallel operation? How to determine these?

1. The capacity and number of diesel generator sets should be comprehensively determined according to the emergency load size and input sequence, as well as the maximum starting capacity of a single motor. When the emergency load is large, multiple units can be used for parallel operation, and the number of units should be 2 to 4 units. When limited by parallel conditions, partition power supply can be implemented. When the power load harmonic is large, its influence on the generator set should be considered.

2. In the preliminary design stage of the scheme, the capacity of diesel generators can be estimated according to 10% to 20% of the total capacity of distribution transformers. In the construction design stage, the maximum capacity calculated by the following methods can be determined according to the capacity of primary load, fire protection load and some important secondary loads:

1) Calculate the capacity of the generator set according to the stable load;

2) Calculate the diesel generator capacity according to the needs of starting the largest single motor or group of motors;

3) Calculate the capacity of the generator set according to the allowable voltage drop of the generator bus when the motor is started.

3. When there is elevator load, the generator bus voltage should not be lower than 80% of the rated voltage in the case of starting the cage motor with the maximum capacity at full voltage; when there is no elevator load, the bus voltage should not be lower than the rated voltage. 75%. When conditions permit, the motor can be started in an automatic step-down mode.

Of course, paralleling is not as easy as imagined, and additional parallel cabinets, fully automatic parallel cabinets and switching cabinets are required. The requirements are also very high, and the parameters, model, power, etc. of the unit need to be strictly considered. Therefore, Starlight recommends that if you have the need for parallel operation, it is best to have the operation performed by professional technicians.

Starlight Power has advanced testing equipment, modern production technology, professional manufacturing technology, perfect quality management system, and strong technical research and development capabilities. It can provide 3KW～2500KW various specifications of ordinary, automatic, four protection, automatic switching, low noise and mobile generator sets, high quality and low energy consumption to meet the diverse power needs of customers, and can also meet users with different voltages and different frequencies. It is required to create a parallel power supply system for multiple units. If you are interested in our product or any question on generator, welcome to send email to sales@dieselgeneratortech.com.