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0MLMHTK65RUENUB
Mechanical Bypass
follows these precautions when operating SWMB
SWMB must not be closed on a UPS that is off and that is connected in parallel with other units operating
normally. This operation may cause a fault on the UPS’s which may create a dangerous voltage at the
output. SWMB may be closed with the UPS operating by following the procedure described in the section
“Operating modes”.
operation not to be executed
If SWMB is closed on any unit, the whole system switches to bypass.
If all the switches are then opened to allow maintenance operations to be carried out, all the power
required by the load will switch onto the mechanical bypass line of the unit in which SWMB has been
closed.
WARNING: both the automatic and the mechanical bypass line of each UPS is sized for the rated
power of the single unit.
NOTE To mechanically bypass the entire UPS system the switches SWMB of all the units must be
closed.
Mechanical bypass on a single unit
This is the procedure to perform a mechanical bypass operation
on a single unit
(e.g. UPS1):
Open switches SWBY, SWOUT, SWIN and the battery cabinet circuit breaker/disconnect on unit 1 only.
If the active UPS’s can power the load, the system remains in normal operation and maintenance can be carried out
on UPS1.
Mechanical bypass on the whole system
The sequences of operations to be carried out to place the system in mechanical bypass are described below. The
procedures vary depending on the initial state:
- All the UPS are in NORMAL OPERATION
procedure a)
the power supplied to the load is not interrupted in any way
;
- whole system with output not synchronized with the bypass line
procedure b)
the power supplied to the load is interrupted
(therefore, this operation should be used only if absolutely necessary).
Procedure a)
The bypass line is present and its frequency and voltage are within the acceptable range.
the
UPS display panel indicates
NORMAL OPERATION.
1.
Close all the switches SWMB (the control logic automatically disables the inverter)
2.
Open all the switches on the UPS (SWIN, SWOUT, SWBY and the battery cabinet circuit
breaker/disconnect) and keep only SWMB (mechanical bypass switch) closed. The control panel
remains off.
After carrying out the above operations, personnel must wait at least ten minutes for the
capacitors to discharge before working on the inside of the UPS.
In this situation, any disturbance (such as a blackout) on the mains supply line will have an effect on the
load (since the batteries are deactivated in this state).
