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A (INV: UNSYNCHRONISED) warning message is displayed on the
operator control panel when the inverter and bypass supplies are not
synchronised; a second manually controlled, ‘maintenance bypass’
supply is also incorporated into the UPS design. Its purpose is to
enable the critical load to be powered from the mains (bypass) supply
while the UPS is shut down for maintenance or troubleshooting.
Note: The load is unprotected against mains power supply aberrations
or failure when it is connected to either the static bypass or maintenance
supply.
The power switch locations in the various 7400-M models are shown
in Figure 1-3. Figure 1-2 illustrates the 7400-M Series UPS module in
what is known as the “Split Bypass” configuration. In the “Split
Bypass” configuration the static bypass line is connected by a separate
power switch to a dedicated “Bypass” power source which also feeds
the maintenance bypass line. Where a separate power source is not
available, the bypass (Q2) and Rectifier input supply connections
would be linked together.
With the exception of the maintenance bypass isolators, all the
isolators shown must be closed during normal UPS operation.
The battery is connected to the DC busbar, through a circuit breaker
fitted inside the battery cabinet or located adjacent to the batteries
where a battery cabinet is not used. This circuit breaker is closed
manually, but it contains an under-voltage release coil which enables
it to be tripped down from the UPS control electronics following
certain detected faults. It also has a magnetic trip facility for overload
protection.
The batteries associated with the UPS are generally housed in a
purpose built cabinet/ racks located alongside the main UPS
equipment.
It is possible to install batteries of various types and capacity in the
cabinet/ rack to obtain the required autonomy characteristics.
The battery cabinet can be purchased in one of the following forms:
1. Complete installation comprising the battery cabinet/ rack,
batteries and circuit breakers.
2. Battery cabinet/ rack and circuit breaker only – with no batteries.
3. Battery cabinet/ rack only – with no batteries or c/b..
As an alternative to the battery cabinet, a battery circuit breaker can
be provided in a custom built box. This Battery Circuit Box is
designed to be wall or rack mounted and is connected between the
UPS and Battery.
For systems with batteries installed in non-optimized temperature
conditions, the 7400-M offers a battery temperature compensation
(optional). As the temperature inside the battery cabinet / area rises
the DC busbar voltage reduces in order to sustain the battery at its
optimum charge voltage. This will assist in prolonging the life of the
batteries.
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