1. The unit capacity and number of units should be determined comprehensively according to factors such as emergency load size and input sequence, as well as the starting capacity of a single motor. When the emergency load is large, multiple machines can be operated in parallel, and the number of units should be 2 to 4. When restricted by parallel conditions, district power supply can be implemented. When the harmonics of the electrical load are large, its impact on the generator should be considered.

2. In the stage of plan and preliminary design, the capacity of diesel generators can be estimated at 10% to 20% of the total capacity of distribution transformers. In the construction drawing design stage, the capacity can be determined according to the capacity of primary load, fire load and some important secondary loads according to the following methods: 1) Calculate the generator capacity according to the stable load; 2) According to the single motor or Calculate the generator capacity for the starting needs of the group motor; 3) Calculate the generator capacity according to the allowable voltage drop of the generator bus when starting the motor.

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

4. When there are multiple units, units and supporting equipment with the same model, specifications and characteristics should be selected.