Quick start_MUST400T_ENG_REV00
10
1.5.1 Rectifier and Bypass Input Supply of the UPS
Over currents
Install suitable protective devices in the distribution unit of the incoming mains supply, considering the power
cable current-carrying capacity and overload capacity of the system (
see Tab. 9-7
). Generally, the magnetic
circuit breaker with IEC60947-2 tripping curve C (normal) at the 125% of the current listed in Tab. 9-7 is
recommended.
Dual input: In case of double mains used, separate protective devices should be installed for the rectifier input
and bypass input in the incoming mains distribution panel.
Note: The rectifier input and bypass input must use the same neutral line
.
So don’t remove the neutral common copper bridge present between input and bypass terminals
Protection against earth faults (RCD devices):
The RCD device installed upstream of the input supply should be comply with:
Sensitive to DC unidirectional pulses (class A) in the network
Insensitive to transient current pulses
Have an average sensitivity that is adjustable between 0.3A and 1A.
Fig.1- 3: The Symbols of RCCB
When using the RCD in the split bypass system or parallel system, the RCD should be installed upstream of
the input distribution to avoid wrong alarm.
The residual current introduced by RFI filter in the UPS is between 3.5mA and 1000mA. It is recommended to
confirm the sensitivity of each RCD of upstream input distribution and downstream distribution (to load).
1.5.2 External Battery
The DC compatible circuit breaker provides over current protection for UPS system and battery, which is
provided by the external battery cabinet.
1.5.3 UPS Output
In case of an external distribution cabinet is used for load distribution, the selection of protective
devices must provide discrimination with those that are used at the input to the UPS
(
see Tab. 9-7
).
