APC 480kW User Manual download pdf (Page 6)

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APC

APPLICATION NOTE

Fig. 3: Top: Output voltage on the diesel generator.

Bottom: Output voltage on 480kW. Here 480kW is loaded with 100% resistive load.

A number of measuring on the 480kW supplied from diesel generator has been carried out. Fig. 1 and 3 show that the ramp-in

time on the generator has an influence on how much the frequency on the generator decreases at ramp-in and on how much

the frequency changes when the ramp-in ends. Therefore some additional tests have been carried out on the 480kW, showing

that if a long ramp-in time is chosen, then the slew rate can be de-creased. This is important if a short ramp-in time is wanted,

because then a higher slew rate time has to be accepted. By installation of systems with diesel generator, both slew rates as

well as ramp-in time have therefore to be adjusted to the used generator. The total conclusion is that 480kW has handled the

diesel operation to satisfaction.

Requirements of the diesel generator

When dimensioning the diesel generator for an APC Silcon UPS is aware of the following recommended requirements:

kVA rating

As APC Silcon has PF 1 on the input, there is no requirement of kVA rating of the generator.

kW rating

When APC Silcon is going to operate on the diesel generator, the batteries of the APC Silcon UPS have already been

discharged. Therefore the generator must take over full charging power, loss in inverter, as well as load.

On figure 4 the input current of the APC Silcon can be calculated using table and curve.

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APC 480kW User Manual Page 6