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Capacity selection and calculation of diesel generators

- Apr 24, 2017 -

When the motor start, the terminal voltage should be able to guarantee the mechanical requirements of the starting torque, and when the starting, the power distribution Busbar voltage should meet the following requirements:
When the motor is not frequent starting, not less than the nominal voltage of 85% (data center room in the diesel generator power supply, the motor is not frequent start);
When the power distribution bus is not connected to the illumination or other voltage-sensitive load, it should not be less than 80% of nominal voltage;
The only motor on the distribution bus can be determined according to the condition of guaranteeing the starting torque of the motor. For low-voltage motors, the contactor coil voltage should also be guaranteed not less than the release voltage (from the product sample, can be found in the sample, can be considered as 70%)
(1) In the capacity of all contingency loads,
SG1--the generator capacity, KVA according to the full contingency load; PSZ--accident illumination Load, kw; the efficiency of illumination load of SZ--accident; TG φ SZ--accident illumination load factor angle tangent; Rated capacity of the PM--motor, KW; The rated efficiency of the ETA M--motor, which can usually be taken by 0.8~0.9 or by product samples; TG φ M--motor power factor angle tangent value; K--need coefficient, in the data center room emergency situation to take 1.
(2) in calculating the power of the generator's overload capacity of the
SG2--the generator capacity, KVA according to the start-up of the large capacity motor which satisfies the need of start-up;
P0--PMmax the load capacity that has been put into operation before the shipment, KVA;
Cos φ 0--P0 load power factor;
The sine of the power factor angle of the sin φ 0--P0 load;
The rated capacity of the maximum capacity motor of PMmax--inputs, KW;
Cos φ Mmax--The starting power factor of the maximum capacity motor;
Sin φ Mmax--the sine of the starting power factor angle of the maximum capacity motor;
KG--Generator is a multiple of the overload, generally desirable 1.5;
β-the equivalent of the KVA value of the PMmax motor starting with the rated capacity of the electric machine;
Beta '= beta/eta mnxcos φ mn
In the upper type, β-the starting current multiples of the motor;
The efficiency of the maximum capacity motor of ETA mn--;
Cos φ mn--The power factor of the maximum capacity motor;
Kq--starting current multiples, see table 2.

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