Specifications

SP121E Rev. 000 Siel S.p.A. Pag. 14 of 42

Issued date: 2005-05-06

GREEN POINT

Differential (Residual Current Device (RCD))

In the standard version, where no input isolation transformer exists, the mains supply input neutral is

connected to the UPS output neutral. The UPS does alter the arrangement of the neutral regime within

the system, as a result, the electrical systems both up stream and down stream are identical.

Additional differential (RCD) devices may be installed on the output of the UPS, corresponding to

those installed on the input.

The differential devices installed on the system input must have the following characteristics:

§ A differential current of not less than 100mA (to avoid nuisance tripping)

§ type A or type B with delay equal to or greater than 0.1 s

The UPS rated output current is indicated in the previous table (under the heading “Output current

rated”)

UPS OUTPUT PROTECTION, SHORT CIRCUIT AND DISCRIMINATION

Short circuit

During a fault within the load or a short circuit, the UPS will limit the amount and the duration of the

current supplied (current limited), in order to protect the UPS inverter output(short circuit current).

The amount of current available will depend upon the operating mode of the UPS at the time of the

fault.

UPS in Normal Operation mode: The load is instantly switched onto the by-pass supply, thus

guaranteeing the values indicated in the technical data section, before the FBY fuse(s) intervenes.

UPS in Battery Operation mode: The UPS protects itself by supplying an output current of

approximately 2 times the rated current for 0.5s.

Discrimination

The following table provides an indication as to the maximum rating and type of fuse that can be

discriminated by the UPS, the table contains two values for each size of UPS, the recommended fuses

are dependent on the operational mode of the UPS when the fault or overload occurs, these being

either Normal Operation or Battery Operation.

UPS with single-phase output

kVA Rating 10 15 20

Max output fuse size & type [A]

Discrimination in Battery Operation mode